qemu-img
Invocationqemu-nbd
InvocationQEMU is a FAST! processor emulator using dynamic translation to achieve good emulation speed.
QEMU has two operating modes:
QEMU has the following features:
QEMU user mode emulation has the following features:
QEMU full system emulation has the following features:
The QEMU PC System emulator simulates the following peripherals:
SMP is supported with up to 255 CPUs.
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 http://www.deinmeister.de/gusemu/) by Tibor "TS" Schütz.
Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU must be told to not have parallel ports to have working GUS.
qemu-system-i386 dos.img -soundhw gus -parallel none
Alternatively:
qemu-system-i386 dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
Download and uncompress the linux image (linux.img) and type:
qemu-system-i386 linux.img
Linux should boot and give you a prompt.
qemu-system-i386
[options] [disk_image]
disk_image is a raw hard disk image for IDE hard disk 0. Some targets do not need a disk image.
Display help and exit
Display version information and exit
Select the emulated machine by name. Use -machine help
to list
available machines.
For architectures which aim to support live migration compatibility across releases, each release will introduce a new versioned machine type. For example, the 2.8.0 release introduced machine types “pc-i440fx-2.8” and “pc-q35-2.8” for the x86_64/i686 architectures.
To allow live migration of guests from QEMU version 2.8.0, to QEMU version 2.9.0, the 2.9.0 version must support the “pc-i440fx-2.8” and “pc-q35-2.8” machines too. To allow users live migrating VMs to skip multiple intermediate releases when upgrading, new releases of QEMU will support machine types from many previous versions.
Supported machine properties are:
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax or tcg can be available. By default, tcg is used. If there is more than one accelerator specified, the next one is used if the previous one fails to initialize.
Controls in-kernel irqchip support for the chosen accelerator when available.
Enables IGD GFX passthrough support for the chosen machine when available.
Enables emulation of VMWare IO port, for vmmouse etc. auto says to select the value based on accel. For accel=xen the default is off otherwise the default is on.
Defines the size of the KVM shadow MMU.
Include guest memory in a core dump. The default is on.
Enables or disables memory merge support. This feature, when supported by the host, de-duplicates identical memory pages among VMs instances (enabled by default).
Enables or disables AES key wrapping support on s390-ccw hosts. This feature controls whether AES wrapping keys will be created to allow execution of AES cryptographic functions. The default is on.
Enables or disables DEA key wrapping support on s390-ccw hosts. This feature controls whether DEA wrapping keys will be created to allow execution of DEA cryptographic functions. The default is on.
Enables or disables NVDIMM support. The default is off.
Enables or disables squashing subchannels into the default css. The default is off.
If enforce-config-section is set to on, force migration code to send configuration section even if the machine-type sets the migration.send-configuration property to off. NOTE: this parameter is deprecated. Please use -global migration.send-configuration=on|off instead.
Select CPU model (-cpu help
for list and additional feature selection)
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax or tcg can be available. By default, tcg is used. If there is more than one accelerator specified, the next one is used if the previous one fails to initialize.
Controls number of TCG threads. When the TCG is multi-threaded there will be one thread per vCPU therefor taking advantage of additional host cores. The default is to enable multi-threading where both the back-end and front-ends support it and no incompatible TCG features have been enabled (e.g. icount/replay).
Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs are supported. On Sparc32 target, Linux limits the number of usable CPUs to 4. For the PC target, the number of cores per socket, the number of threads per cores and the total number of sockets can be specified. Missing values will be computed. If any on the three values is given, the total number of CPUs n can be omitted. maxcpus specifies the maximum number of hotpluggable CPUs.
Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA distance from a source node to a destination node.
Legacy VCPU assignment uses ‘cpus’ option where firstcpu and lastcpu are CPU indexes. Each ‘cpus’ option represent a contiguous range of CPU indexes (or a single VCPU if lastcpu is omitted). A non-contiguous set of VCPUs can be represented by providing multiple ‘cpus’ options. If ‘cpus’ is omitted on all nodes, VCPUs are automatically split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to a NUMA node:
-numa node,cpus=0-2,cpus=5
‘cpu’ option is a new alternative to ‘cpus’ option which uses ‘socket-id|core-id|thread-id’ properties to assign CPU objects to a node using topology layout properties of CPU. The set of properties is machine specific, and depends on used machine type/‘smp’ options. It could be queried with ‘hotpluggable-cpus’ monitor command. ‘node-id’ property specifies node to which CPU object will be assigned, it’s required for node to be declared with ‘node’ option before it’s used with ‘cpu’ option.
For example:
-M pc \ -smp 1,sockets=2,maxcpus=2 \ -numa node,nodeid=0 -numa node,nodeid=1 \ -numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
‘mem’ assigns a given RAM amount to a node. ‘memdev’ assigns RAM from a given memory backend device to a node. If ‘mem’ and ‘memdev’ are omitted in all nodes, RAM is split equally between them.
‘mem’ and ‘memdev’ are mutually exclusive. Furthermore, if one node uses ‘memdev’, all of them have to use it.
source and destination are NUMA node IDs. distance is the NUMA distance from source to destination. The distance from a node to itself is always 10. If any pair of nodes is given a distance, then all pairs must be given distances. Although, when distances are only given in one direction for each pair of nodes, then the distances in the opposite directions are assumed to be the same. If, however, an asymmetrical pair of distances is given for even one node pair, then all node pairs must be provided distance values for both directions, even when they are symmetrical. When a node is unreachable from another node, set the pair’s distance to 255.
Note that the -numa option doesn’t allocate any of the specified resources, it just assigns existing resources to NUMA nodes. This means that one still has to use the -m, -smp options to allocate RAM and VCPUs respectively.
Add a file descriptor to an fd set. Valid options are:
This option defines the file descriptor of which a duplicate is added to fd set. The file descriptor cannot be stdin, stdout, or stderr.
This option defines the ID of the fd set to add the file descriptor to.
This option defines a free-form string that can be used to describe fd.
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" -drive file=/dev/fdset/2,index=0,media=disk
Set parameter arg for item id of type group
Set default value of driver’s property prop to value, e.g.:
qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img
In particular, you can use this to set driver properties for devices which are created automatically by the machine model. To create a device which is not created automatically and set properties on it, use -device.
-global driver.prop=value is shorthand for -global driver=driver,property=prop,value=value. The longhand syntax works even when driver contains a dot.
Specify boot order drives as a string of drive letters. Valid drive letters depend on the target architecture. The x86 PC uses: a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p (Etherboot from network adapter 1-4), hard disk boot is the default. To apply a particular boot order only on the first startup, specify it via once. Note that the order or once parameter should not be used together with the bootindex property of devices, since the firmware implementations normally do not support both at the same time.
Interactive boot menus/prompts can be enabled via menu=on as far as firmware/BIOS supports them. The default is non-interactive boot.
A splash picture could be passed to bios, enabling user to show it as logo, when option splash=sp_name is given and menu=on, If firmware/BIOS supports them. Currently Seabios for X86 system support it. limitation: The splash file could be a jpeg file or a BMP file in 24 BPP format(true color). The resolution should be supported by the SVGA mode, so the recommended is 320x240, 640x480, 800x640.
A timeout could be passed to bios, guest will pause for rb_timeout ms when boot failed, then reboot. If rb_timeout is ’-1’, guest will not reboot, qemu passes ’-1’ to bios by default. Currently Seabios for X86 system support it.
Do strict boot via strict=on as far as firmware/BIOS supports it. This only effects when boot priority is changed by bootindex options. The default is non-strict boot.
# try to boot from network first, then from hard disk qemu-system-i386 -boot order=nc # boot from CD-ROM first, switch back to default order after reboot qemu-system-i386 -boot once=d # boot with a splash picture for 5 seconds. qemu-system-i386 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format ’-boot drives’ is still supported but its use is discouraged as it may be removed from future versions.
Sets guest startup RAM size to megs megabytes. Default is 128 MiB. Optionally, a suffix of “M” or “G” can be used to signify a value in megabytes or gigabytes respectively. Optional pair slots, maxmem could be used to set amount of hotpluggable memory slots and maximum amount of memory. Note that maxmem must be aligned to the page size.
For example, the following command-line sets the guest startup RAM size to 1GB, creates 3 slots to hotplug additional memory and sets the maximum memory the guest can reach to 4GB:
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
If slots and maxmem are not specified, memory hotplug won’t be enabled and the guest startup RAM will never increase.
Allocate guest RAM from a temporarily created file in path.
Preallocate memory when using -mem-path.
Use keyboard layout language (for example fr
for
French). This option is only needed where it is not easy to get raw PC
keycodes (e.g. on Macs, with some X11 servers or with a VNC or curses
display). You don’t normally need to use it on PC/Linux or PC/Windows
hosts.
The available layouts are:
ar de-ch es fo fr-ca hu ja mk no pt-br sv da en-gb et fr fr-ch is lt nl pl ru th de en-us fi fr-be hr it lv nl-be pt sl tr
The default is en-us
.
Will show the audio subsystem help: list of drivers, tunable parameters.
Enable audio and selected sound hardware. Use ’help’ to print all available sound hardware.
qemu-system-i386 -soundhw sb16,adlib disk.img qemu-system-i386 -soundhw es1370 disk.img qemu-system-i386 -soundhw ac97 disk.img qemu-system-i386 -soundhw hda disk.img qemu-system-i386 -soundhw all disk.img qemu-system-i386 -soundhw help
Note that Linux’s i810_audio OSS kernel (for AC97) module might require manually specifying clocking.
modprobe i810_audio clocking=48000
Disable balloon device.
Enable virtio balloon device (default), optionally with PCI address addr.
Add device driver. prop=value sets driver
properties. Valid properties depend on the driver. To get help on
possible drivers and properties, use -device help
and
-device driver,help
.
Some drivers are:
Add an IPMI BMC. This is a simulation of a hardware management interface processor that normally sits on a system. It provides a watchdog and the ability to reset and power control the system. You need to connect this to an IPMI interface to make it useful
The IPMI slave address to use for the BMC. The default is 0x20. This address is the BMC’s address on the I2C network of management controllers. If you don’t know what this means, it is safe to ignore it.
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
Define slave address to use for the BMC. The default is 0x20.
file containing raw Sensor Data Records (SDR) data. The default is none.
size of a Field Replaceable Unit (FRU) area. The default is 1024.
file containing raw Field Replaceable Unit (FRU) inventory data. The default is none.
Add a connection to an external IPMI BMC simulator. Instead of locally emulating the BMC like the above item, instead connect to an external entity that provides the IPMI services.
A connection is made to an external BMC simulator. If you do this, it is strongly recommended that you use the "reconnect=" chardev option to reconnect to the simulator if the connection is lost. Note that if this is not used carefully, it can be a security issue, as the interface has the ability to send resets, NMIs, and power off the VM. It’s best if QEMU makes a connection to an external simulator running on a secure port on localhost, so neither the simulator nor QEMU is exposed to any outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for more details on the external interface.
Add a KCS IPMI interafce on the ISA bus. This also adds a corresponding ACPI and SMBIOS entries, if appropriate.
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
Define the I/O address of the interface. The default is 0xca0 for KCS.
Define the interrupt to use. The default is 5. To disable interrupts, set this to 0.
Like the KCS interface, but defines a BT interface. The default port is 0xe4 and the default interrupt is 5.
Sets the name of the guest. This name will be displayed in the SDL window caption. The name will also be used for the VNC server. Also optionally set the top visible process name in Linux. Naming of individual threads can also be enabled on Linux to aid debugging.
Set system UUID.
Use file as floppy disk 0/1 image (see disk_images).
Use file as hard disk 0, 1, 2 or 3 image (see disk_images).
Use file as CD-ROM image (you cannot use -hdc and -cdrom at the same time). You can use the host CD-ROM by using /dev/cdrom as filename (see host_drives).
Define a new block driver node. Some of the options apply to all block drivers, other options are only accepted for a specific block driver. See below for a list of generic options and options for the most common block drivers.
Options that expect a reference to another node (e.g. file
) can be
given in two ways. Either you specify the node name of an already existing node
(file=node-name), or you define a new node inline, adding options
for the referenced node after a dot (file.filename=path,file.aio=native).
A block driver node created with -blockdev can be used for a guest
device by specifying its node name for the drive
property in a
-device argument that defines a block device.
driver
Specifies the block driver to use for the given node.
node-name
This defines the name of the block driver node by which it will be referenced later. The name must be unique, i.e. it must not match the name of a different block driver node, or (if you use -drive as well) the ID of a drive.
If no node name is specified, it is automatically generated. The generated node name is not intended to be predictable and changes between QEMU invocations. For the top level, an explicit node name must be specified.
read-only
Open the node read-only. Guest write attempts will fail.
cache.direct
The host page cache can be avoided with cache.direct=on. This will attempt to do disk IO directly to the guest’s memory. QEMU may still perform an internal copy of the data.
cache.no-flush
In case you don’t care about data integrity over host failures, you can use cache.no-flush=on. This option tells QEMU that it never needs to write any data to the disk but can instead keep things in cache. If anything goes wrong, like your host losing power, the disk storage getting disconnected accidentally, etc. your image will most probably be rendered unusable.
discard=discard
discard is one of "ignore" (or "off") or "unmap" (or "on") and controls
whether discard
(also known as trim
or unmap
) requests are
ignored or passed to the filesystem. Some machine types may not support
discard requests.
detect-zeroes=detect-zeroes
detect-zeroes is "off", "on" or "unmap" and enables the automatic
conversion of plain zero writes by the OS to driver specific optimized
zero write commands. You may even choose "unmap" if discard is set
to "unmap" to allow a zero write to be converted to an unmap
operation.
file
This is the protocol-level block driver for accessing regular files.
filename
The path to the image file in the local filesystem
aio
Specifies the AIO backend (threads/native, default: threads)
Example:
-blockdev driver=file,node-name=disk,filename=disk.img
raw
This is the image format block driver for raw images. It is usually
stacked on top of a protocol level block driver such as file
.
file
Reference to or definition of the data source block driver node
(e.g. a file
driver node)
Example 1:
-blockdev driver=file,node-name=disk_file,filename=disk.img -blockdev driver=raw,node-name=disk,file=disk_file
Example 2:
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
qcow2
This is the image format block driver for qcow2 images. It is usually
stacked on top of a protocol level block driver such as file
.
file
Reference to or definition of the data source block driver node
(e.g. a file
driver node)
backing
Reference to or definition of the backing file block device (default is taken from the image file). It is allowed to pass an empty string here in order to disable the default backing file.
lazy-refcounts
Whether to enable the lazy refcounts feature (on/off; default is taken from the image file)
cache-size
The maximum total size of the L2 table and refcount block caches in bytes (default: 1048576 bytes or 8 clusters, whichever is larger)
l2-cache-size
The maximum size of the L2 table cache in bytes (default: 4/5 of the total cache size)
refcount-cache-size
The maximum size of the refcount block cache in bytes (default: 1/5 of the total cache size)
cache-clean-interval
Clean unused entries in the L2 and refcount caches. The interval is in seconds. The default value is 0 and it disables this feature.
pass-discard-request
Whether discard requests to the qcow2 device should be forwarded to the data source (on/off; default: on if discard=unmap is specified, off otherwise)
pass-discard-snapshot
Whether discard requests for the data source should be issued when a snapshot operation (e.g. deleting a snapshot) frees clusters in the qcow2 file (on/off; default: on)
pass-discard-other
Whether discard requests for the data source should be issued on other occasions where a cluster gets freed (on/off; default: off)
overlap-check
Which overlap checks to perform for writes to the image
(none/constant/cached/all; default: cached). For details or finer
granularity control refer to the QAPI documentation of blockdev-add
.
Example 1:
-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2 -blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
Example 2:
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
Please refer to the QAPI documentation of the blockdev-add
QMP command.
Define a new drive. This includes creating a block driver node (the backend) as well as a guest device, and is mostly a shortcut for defining the corresponding -blockdev and -device options.
-drive accepts all options that are accepted by -blockdev. In addition, it knows the following options:
This option defines which disk image (see disk_images) to use with this drive. If the filename contains comma, you must double it (for instance, "file=my,,file" to use file "my,file").
Special files such as iSCSI devices can be specified using protocol specific URLs. See the section for "Device URL Syntax" for more information.
This option defines on which type on interface the drive is connected. Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio, none.
These options define where is connected the drive by defining the bus number and the unit id.
This option defines where is connected the drive by using an index in the list of available connectors of a given interface type.
This option defines the type of the media: disk or cdrom.
These options have the same definition as they have in -hdachs.
These parameters are deprecated, use the corresponding parameters
of -device
instead.
snapshot is "on" or "off" and controls snapshot mode for the given drive (see -snapshot).
cache is "none", "writeback", "unsafe", "directsync" or "writethrough" and controls how the host cache is used to access block data. This is a shortcut that sets the cache.direct and cache.no-flush options (as in -blockdev), and additionally cache.writeback, which provides a default for the write-cache option of block guest devices (as in -device).
Specify which disk format will be used rather than detecting the format. Can be used to specify format=raw to avoid interpreting an untrusted format header.
This option specifies the serial number to assign to the device. This
parameter is deprecated, use the corresponding parameter of -device
instead.
Specify the controller’s PCI address (if=virtio only). This parameter is
deprecated, use the corresponding parameter of -device
instead.
Specify which action to take on write and read errors. Valid actions are: "ignore" (ignore the error and try to continue), "stop" (pause QEMU), "report" (report the error to the guest), "enospc" (pause QEMU only if the host disk is full; report the error to the guest otherwise). The default setting is werror=enospc and rerror=report.
copy-on-read is "on" or "off" and enables whether to copy read backing file sectors into the image file.
Specify bandwidth throttling limits in bytes per second, either for all request types or for reads or writes only. Small values can lead to timeouts or hangs inside the guest. A safe minimum for disks is 2 MB/s.
Specify bursts in bytes per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily.
Specify request rate limits in requests per second, either for all request types or for reads or writes only.
Specify bursts in requests per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily.
Let every is bytes of a request count as a new request for iops throttling purposes. Use this option to prevent guests from circumventing iops limits by sending fewer but larger requests.
Join a throttling quota group with given name g. All drives that are members of the same group are accounted for together. Use this option to prevent guests from circumventing throttling limits by using many small disks instead of a single larger disk.
By default, the cache.writeback=on mode is used. It will report data writes as completed as soon as the data is present in the host page cache. This is safe as long as your guest OS makes sure to correctly flush disk caches where needed. If your guest OS does not handle volatile disk write caches correctly and your host crashes or loses power, then the guest may experience data corruption.
For such guests, you should consider using cache.writeback=off. This means that the host page cache will be used to read and write data, but write notification will be sent to the guest only after QEMU has made sure to flush each write to the disk. Be aware that this has a major impact on performance.
When using the -snapshot option, unsafe caching is always used.
Copy-on-read avoids accessing the same backing file sectors repeatedly and is useful when the backing file is over a slow network. By default copy-on-read is off.
Instead of -cdrom you can use:
qemu-system-i386 -drive file=file,index=2,media=cdrom
Instead of -hda, -hdb, -hdc, -hdd, you can use:
qemu-system-i386 -drive file=file,index=0,media=disk qemu-system-i386 -drive file=file,index=1,media=disk qemu-system-i386 -drive file=file,index=2,media=disk qemu-system-i386 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" -drive file=/dev/fdset/2,index=0,media=disk
You can connect a CDROM to the slave of ide0:
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
If you don’t specify the "file=" argument, you define an empty drive:
qemu-system-i386 -drive if=ide,index=1,media=cdrom
Instead of -fda, -fdb, you can use:
qemu-system-i386 -drive file=file,index=0,if=floppy qemu-system-i386 -drive file=file,index=1,if=floppy
By default, interface is "ide" and index is automatically incremented:
qemu-system-i386 -drive file=a -drive file=b"
is interpreted like:
qemu-system-i386 -hda a -hdb b
Use file as on-board Flash memory image.
Use file as SecureDigital card image.
Use file as a parallel flash image.
Write to temporary files instead of disk image files. In this case, the raw disk image you use is not written back. You can however force the write back by pressing C-a s (see disk_images).
Force hard disk 0 physical geometry (1 <= c <= 16383, 1 <=
h <= 16, 1 <= s <= 63) and optionally force the BIOS
translation mode (t=none, lba or auto). Usually QEMU can guess
all those parameters. This option is deprecated, please use
-device ide-hd,cyls=c,heads=h,secs=s,...
instead.
Define a new file system device. Valid options are:
This option specifies the fs driver backend to use. Currently "local", "handle" and "proxy" file system drivers are supported.
Specifies identifier for this device
Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest.
Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files are stored using the same credentials as they are created on the guest. This requires QEMU to run as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these attributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" security model is same as passthrough except the sever won’t report failures if it fails to set file attributes like ownership. Security model is mandatory only for local fsdriver. Other fsdrivers (like handle, proxy) don’t take security model as a parameter.
This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notification will be sent to the guest only when the data has been reported as written by the storage subsystem.
Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.
Enables proxy filesystem driver to use passed socket file for communicating with virtfs-proxy-helper
Enables proxy filesystem driver to use passed socket descriptor for communicating with virtfs-proxy-helper. Usually a helper like libvirt will create socketpair and pass one of the fds as sock_fd
Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file".
Specifies the default mode for newly created directories on the host. Works only with security models "mapped-xattr" and "mapped-file".
-fsdev option is used along with -device driver "virtio-9p-pci".
Options for virtio-9p-pci driver are:
Specifies the id value specified along with -fsdev option
Specifies the tag name to be used by the guest to mount this export point
The general form of a Virtual File system pass-through options are:
This option specifies the fs driver backend to use. Currently "local", "handle" and "proxy" file system drivers are supported.
Specifies identifier for this device
Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest.
Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files are stored using the same credentials as they are created on the guest. This requires QEMU to run as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these attributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" security model is same as passthrough except the sever won’t report failures if it fails to set file attributes like ownership. Security model is mandatory only for local fsdriver. Other fsdrivers (like handle, proxy) don’t take security model as a parameter.
This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notification will be sent to the guest only when the data has been reported as written by the storage subsystem.
Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.
Enables proxy filesystem driver to use passed socket file for communicating with virtfs-proxy-helper. Usually a helper like libvirt will create socketpair and pass one of the fds as sock_fd
Enables proxy filesystem driver to use passed ’sock_fd’ as the socket descriptor for interfacing with virtfs-proxy-helper
Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file".
Specifies the default mode for newly created directories on the host. Works only with security models "mapped-xattr" and "mapped-file".
Create synthetic file system image
Enable the USB driver (if it is not used by default yet).
Add the USB device devname. Note that this option is deprecated,
please use -device usb-...
instead. See usb_devices.
Virtual Mouse. This will override the PS/2 mouse emulation when activated.
Pointer device that uses absolute coordinates (like a touchscreen). This means QEMU is able to report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse emulation when activated.
Mass storage device based on file. The optional format argument
will be used rather than detecting the format. Can be used to specify
format=raw
to avoid interpreting an untrusted format header.
Pass through the host device identified by bus.addr (Linux only).
Pass through the host device identified by vendor_id:product_id (Linux only).
Serial converter to host character device dev, see -serial
for the
available devices.
Braille device. This will use BrlAPI to display the braille output on a real or fake device.
Network adapter that supports CDC ethernet and RNDIS protocols.
Select type of display to use. This option is a replacement for the old style -sdl/-curses/... options. Valid values for type are
Display video output via SDL (usually in a separate graphics window; see the SDL documentation for other possibilities).
Display video output via curses. For graphics device models which support a text mode, QEMU can display this output using a curses/ncurses interface. Nothing is displayed when the graphics device is in graphical mode or if the graphics device does not support a text mode. Generally only the VGA device models support text mode.
Do not display video output. The guest will still see an emulated graphics card, but its output will not be displayed to the QEMU user. This option differs from the -nographic option in that it only affects what is done with video output; -nographic also changes the destination of the serial and parallel port data.
Display video output in a GTK window. This interface provides drop-down menus and other UI elements to configure and control the VM during runtime.
Start a VNC server on display <arg>
Normally, if QEMU is compiled with graphical window support, it displays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, you can totally disable graphical output so that QEMU is a simple command line application. The emulated serial port is redirected on the console and muxed with the monitor (unless redirected elsewhere explicitly). Therefore, you can still use QEMU to debug a Linux kernel with a serial console. Use C-a h for help on switching between the console and monitor.
Normally, if QEMU is compiled with graphical window support, it displays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, QEMU can display the VGA output when in text mode using a curses/ncurses interface. Nothing is displayed in graphical mode.
Do not use decorations for SDL windows and start them using the whole available screen space. This makes the using QEMU in a dedicated desktop workspace more convenient.
Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt). Note that this also affects the special keys (for fullscreen, monitor-mode switching, etc).
Use Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note that this also affects the special keys (for fullscreen, monitor-mode switching, etc).
Disable SDL window close capability.
Enable SDL.
Enable the spice remote desktop protocol. Valid options are
Set the TCP port spice is listening on for plaintext channels.
Set the IP address spice is listening on. Default is any address.
Force using the specified IP version.
Set the password you need to authenticate.
Require that the client use SASL to authenticate with the spice. The exact choice of authentication method used is controlled from the system / user’s SASL configuration file for the ’qemu’ service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate locations for the service config. While some SASL auth methods can also provide data encryption (eg GSSAPI), it is recommended that SASL always be combined with the ’tls’ and ’x509’ settings to enable use of SSL and server certificates. This ensures a data encryption preventing compromise of authentication credentials.
Allow client connects without authentication.
Disable copy paste between the client and the guest.
Disable spice-vdagent based file-xfer between the client and the guest.
Set the TCP port spice is listening on for encrypted channels.
Set the x509 file directory. Expects same filenames as -vnc $display,x509=$dir
The x509 file names can also be configured individually.
Specify which ciphers to use.
Force specific channel to be used with or without TLS encryption. The options can be specified multiple times to configure multiple channels. The special name "default" can be used to set the default mode. For channels which are not explicitly forced into one mode the spice client is allowed to pick tls/plaintext as he pleases.
Configure image compression (lossless). Default is auto_glz.
Configure wan image compression (lossy for slow links). Default is auto.
Configure video stream detection. Default is off.
Enable/disable passing mouse events via vdagent. Default is on.
Enable/disable audio stream compression (using celt 0.5.1). Default is on.
Enable/disable spice seamless migration. Default is off.
Enable/disable OpenGL context. Default is off.
DRM render node for OpenGL rendering. If not specified, it will pick the first available. (Since 2.9)
Rotate graphical output 90 deg left (only PXA LCD).
Rotate graphical output some deg left (only PXA LCD).
Select type of VGA card to emulate. Valid values for type are
Cirrus Logic GD5446 Video card. All Windows versions starting from Windows 95 should recognize and use this graphic card. For optimal performances, use 16 bit color depth in the guest and the host OS. (This card was the default before QEMU 2.2)
Standard VGA card with Bochs VBE extensions. If your guest OS supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if you want to use high resolution modes (>= 1280x1024x16) then you should use this option. (This card is the default since QEMU 2.2)
VMWare SVGA-II compatible adapter. Use it if you have sufficiently recent XFree86/XOrg server or Windows guest with a driver for this card.
QXL paravirtual graphic card. It is VGA compatible (including VESA 2.0 VBE support). Works best with qxl guest drivers installed though. Recommended choice when using the spice protocol.
(sun4m only) Sun TCX framebuffer. This is the default framebuffer for sun4m machines and offers both 8-bit and 24-bit colour depths at a fixed resolution of 1024x768.
(sun4m only) Sun cgthree framebuffer. This is a simple 8-bit framebuffer for sun4m machines available in both 1024x768 (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people wishing to run older Solaris versions.
Virtio VGA card.
Disable VGA card.
Start in full screen.
Set the initial graphical resolution and depth (PPC, SPARC only).
Normally, if QEMU is compiled with graphical window support, it displays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, you can have QEMU listen on VNC display display and redirect the VGA display over the VNC session. It is very useful to enable the usb tablet device when using this option (option -device usb-tablet). When using the VNC display, you must use the -k parameter to set the keyboard layout if you are not using en-us. Valid syntax for the display is
With this option, QEMU will try next available VNC displays, until the number L, if the origianlly defined "-vnc display" is not available, e.g. port 5900+display is already used by another application. By default, to=0.
TCP connections will only be allowed from host on display d. By convention the TCP port is 5900+d. Optionally, host can be omitted in which case the server will accept connections from any host.
Connections will be allowed over UNIX domain sockets where path is the location of a unix socket to listen for connections on.
VNC is initialized but not started. The monitor change
command
can be used to later start the VNC server.
Following the display value there may be one or more option flags separated by commas. Valid options are
Connect to a listening VNC client via a “reverse” connection. The
client is specified by the display. For reverse network
connections (host:d,reverse
), the d argument
is a TCP port number, not a display number.
Opens an additional TCP listening port dedicated to VNC Websocket connections.
If a bare websocket option is given, the Websocket port is
5700+display. An alternative port can be specified with the
syntax websocket
=port.
If host is specified connections will only be allowed from this host.
It is possible to control the websocket listen address independently, using
the syntax websocket
=host:port.
If no TLS credentials are provided, the websocket connection runs in unencrypted mode. If TLS credentials are provided, the websocket connection requires encrypted client connections.
Require that password based authentication is used for client connections.
The password must be set separately using the set_password
command in
the pcsys_monitor. The syntax to change your password is:
set_password <protocol> <password>
where <protocol> could be either
"vnc" or "spice".
If you would like to change <protocol> password expiration, you should use
expire_password <protocol> <expiration-time>
where expiration time could
be one of the following options: now, never, +seconds or UNIX time of
expiration, e.g. +60 to make password expire in 60 seconds, or<PHONE_NUMBER>
to make password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for this
date and time).
You can also use keywords "now" or "never" for the expiration time to allow <protocol> password to expire immediately or never expire.
Provides the ID of a set of TLS credentials to use to secure the VNC server. They will apply to both the normal VNC server socket and the websocket socket (if enabled). Setting TLS credentials will cause the VNC server socket to enable the VeNCrypt auth mechanism. The credentials should have been previously created using the -object tls-creds argument.
The tls-creds parameter obsoletes the tls, x509, and x509verify options, and as such it is not permitted to set both new and old type options at the same time.
Require that client use TLS when communicating with the VNC server. This uses anonymous TLS credentials so is susceptible to a man-in-the-middle attack. It is recommended that this option be combined with either the x509 or x509verify options.
This option is now deprecated in favor of using the tls-creds argument.
Valid if tls is specified. Require that x509 credentials are used for negotiating the TLS session. The server will send its x509 certificate to the client. It is recommended that a password be set on the VNC server to provide authentication of the client when this is used. The path following this option specifies where the x509 certificates are to be loaded from. See the vnc_security section for details on generating certificates.
This option is now deprecated in favour of using the tls-creds argument.
Valid if tls is specified. Require that x509 credentials are used for negotiating the TLS session. The server will send its x509 certificate to the client, and request that the client send its own x509 certificate. The server will validate the client’s certificate against the CA certificate, and reject clients when validation fails. If the certificate authority is trusted, this is a sufficient authentication mechanism. You may still wish to set a password on the VNC server as a second authentication layer. The path following this option specifies where the x509 certificates are to be loaded from. See the vnc_security section for details on generating certificates.
This option is now deprecated in favour of using the tls-creds argument.
Require that the client use SASL to authenticate with the VNC server. The exact choice of authentication method used is controlled from the system / user’s SASL configuration file for the ’qemu’ service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate locations for the service config. While some SASL auth methods can also provide data encryption (eg GSSAPI), it is recommended that SASL always be combined with the ’tls’ and ’x509’ settings to enable use of SSL and server certificates. This ensures a data encryption preventing compromise of authentication credentials. See the vnc_security section for details on using SASL authentication.
Turn on access control lists for checking of the x509 client certificate
and SASL party. For x509 certs, the ACL check is made against the
certificate’s distinguished name. This is something that looks like
C=GB,O=ACME,L=Boston,CN=bob
. For SASL party, the ACL check is
made against the username, which depending on the SASL plugin, may
include a realm component, eg bob
or<EMAIL_ADDRESS>.
When the acl flag is set, the initial access list will be
empty, with a deny
policy. Thus no one will be allowed to
use the VNC server until the ACLs have been loaded. This can be
achieved using the acl
monitor command.
Enable lossy compression methods (gradient, JPEG, ...). If this option is set, VNC client may receive lossy framebuffer updates depending on its encoding settings. Enabling this option can save a lot of bandwidth at the expense of quality.
Disable adaptive encodings. Adaptive encodings are enabled by default. An adaptive encoding will try to detect frequently updated screen regions, and send updates in these regions using a lossy encoding (like JPEG). This can be really helpful to save bandwidth when playing videos. Disabling adaptive encodings restores the original static behavior of encodings like Tight.
Set display sharing policy. ’allow-exclusive’ allows clients to ask for exclusive access. As suggested by the rfb spec this is implemented by dropping other connections. Connecting multiple clients in parallel requires all clients asking for a shared session (vncviewer: -shared switch). This is the default. ’force-shared’ disables exclusive client access. Useful for shared desktop sessions, where you don’t want someone forgetting specify -shared disconnect everybody else. ’ignore’ completely ignores the shared flag and allows everybody connect unconditionally. Doesn’t conform to the rfb spec but is traditional QEMU behavior.
Set keyboard delay, for key down and key up events, in milliseconds. Default is 10. Keyboards are low-bandwidth devices, so this slowdown can help the device and guest to keep up and not lose events in case events are arriving in bulk. Possible causes for the latter are flaky network connections, or scripts for automated testing.
Use it when installing Windows 2000 to avoid a disk full bug. After Windows 2000 is installed, you no longer need this option (this option slows down the IDE transfers).
Disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy disks.
Disable ACPI (Advanced Configuration and Power Interface) support.
Disable HPET support.
Add ACPI table with specified header fields and context from specified files. For file=, take whole ACPI table from the specified files, including all ACPI headers (possible overridden by other options). For data=, only data portion of the table is used, all header information is specified in the command line. If a SLIC table is supplied to QEMU, then the SLIC’s oem_id and oem_table_id fields will override the same in the RSDT and the FADT (a.k.a. FACP), in order to ensure the field matches required by the Microsoft SLIC spec and the ACPI spec.
Load SMBIOS entry from binary file.
Specify SMBIOS type 0 fields
Specify SMBIOS type 1 fields
Specify SMBIOS type 2 fields
Specify SMBIOS type 3 fields
Specify SMBIOS type 4 fields
Specify SMBIOS type 17 fields
Create a new Network Interface Card and connect it to VLAN n (n
= 0 is the default). The NIC is an e1000 by default on the PC
target. Optionally, the MAC address can be changed to mac, the
device address set to addr (PCI cards only),
and a name can be assigned for use in monitor commands.
Optionally, for PCI cards, you can specify the number v of MSI-X vectors
that the card should have; this option currently only affects virtio cards; set
v = 0 to disable MSI-X. If no -net option is specified, a single
NIC is created. QEMU can emulate several different models of network card.
Valid values for type are
virtio
, i82551
, i82557b
, i82559er
,
ne2k_pci
, ne2k_isa
, pcnet
, rtl8139
,
e1000
, smc91c111
, lance
and mcf_fec
.
Not all devices are supported on all targets. Use -net nic,model=help
for a list of available devices for your target.
Use the user mode network stack which requires no administrator privilege to run. Valid options are:
Connect user mode stack to VLAN n (n = 0 is the default).
Assign symbolic name for use in monitor commands.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be enabled. If neither is specified both protocols are enabled.
Set IP network address the guest will see. Optionally specify the netmask, either in the form a.b.c.d or as number of valid top-most bits. Default is <IP_ADDRESS>/24.
Specify the guest-visible address of the host. Default is the 2nd IP in the guest network, i.e. x.x.x.2.
Set IPv6 network address the guest will see (default is fec0::/64). The network prefix is given in the usual hexadecimal IPv6 address notation. The prefix size is optional, and is given as the number of valid top-most bits (default is 64).
Specify the guest-visible IPv6 address of the host. Default is the 2nd IPv6 in the guest network, i.e. xxxx::2.
If this option is enabled, the guest will be isolated, i.e. it will not be able to contact the host and no guest IP packets will be routed over the host to the outside. This option does not affect any explicitly set forwarding rules.
Specifies the client hostname reported by the built-in DHCP server.
Specify the first of the 16 IPs the built-in DHCP server can assign. Default is the 15th to 31st IP in the guest network, i.e. x.x.x.15 to x.x.x.31.
Specify the guest-visible address of the virtual nameserver. The address must be different from the host address. Default is the 3rd IP in the guest network, i.e. x.x.x.3.
Specify the guest-visible address of the IPv6 virtual nameserver. The address must be different from the host address. Default is the 3rd IP in the guest network, i.e. xxxx::3.
Provides an entry for the domain-search list sent by the built-in DHCP server. More than one domain suffix can be transmitted by specifying this option multiple times. If supported, this will cause the guest to automatically try to append the given domain suffix(es) in case a domain name can not be resolved.
Example:
qemu -net user,dnssearch=mgmt.example.org,dnssearch=example.org [...]
When using the user mode network stack, activate a built-in TFTP
server. The files in dir will be exposed as the root of a TFTP server.
The TFTP client on the guest must be configured in binary mode (use the command
bin
of the Unix TFTP client).
When using the user mode network stack, broadcast file as the BOOTP filename. In conjunction with tftp, this can be used to network boot a guest from a local directory.
Example (using pxelinux):
qemu-system-i386 -hda linux.img -boot n -net user,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
When using the user mode network stack, activate a built-in SMB server so that Windows OSes can access to the host files in dir transparently. The IP address of the SMB server can be set to addr. By default the 4th IP in the guest network is used, i.e. x.x.x.4.
In the guest Windows OS, the line:
<IP_ADDRESS> smbserver
must be added in the file C:\WINDOWS\LMHOSTS (for windows 9x/Me) or C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows NT/2000).
Then dir can be accessed in \\smbserver\qemu.
Note that a SAMBA server must be installed on the host OS. QEMU was tested successfully with smbd versions from Red Hat 9, Fedora Core 3 and OpenSUSE 11.x.
Redirect incoming TCP or UDP connections to the host port hostport to the guest IP address guestaddr on guest port guestport. If guestaddr is not specified, its value is x.x.x.15 (default first address given by the built-in DHCP server). By specifying hostaddr, the rule can be bound to a specific host interface. If no connection type is set, TCP is used. This option can be given multiple times.
For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following:
# on the host qemu-system-i386 -net user,hostfwd=tcp:<IP_ADDRESS>:6001-:6000 [...] # this host xterm should open in the guest X11 server xterm -display :1
To redirect telnet connections from host port 5555 to telnet port on the guest, use the following:
# on the host qemu-system-i386 -net user,hostfwd=tcp::5555-:23 [...] telnet localhost 5555
Then when you use on the host telnet localhost 5555
, you
connect to the guest telnet server.
Forward guest TCP connections to the IP address server on port port to the character device dev or to a program executed by cmd:command which gets spawned for each connection. This option can be given multiple times.
You can either use a chardev directly and have that one used throughout QEMU’s lifetime, like in the following example:
# open <IP_ADDRESS>:4321 on bootup, connect <IP_ADDRESS>:1234 to it whenever # the guest accesses it qemu -net user,guestfwd=tcp:<IP_ADDRESS>:1234-tcp:<IP_ADDRESS>:4321 [...]
Or you can execute a command on every TCP connection established by the guest, so that QEMU behaves similar to an inetd process for that virtual server:
# call "netcat <IP_ADDRESS> 4321" on every TCP connection to <IP_ADDRESS>:1234 # and connect the TCP stream to its stdin/stdout qemu -net 'user,guestfwd=tcp:<IP_ADDRESS>:1234-cmd:netcat <IP_ADDRESS> 4321'
Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are still processed and applied to -net user. Mixing them with the new configuration syntax gives undefined results. Their use for new applications is discouraged as they will be removed from future versions.
Connect the host TAP network interface name to VLAN n.
Use the network script file to configure it and the network script dfile to deconfigure it. If name is not provided, the OS automatically provides one. The default network configure script is /etc/qemu-ifup and the default network deconfigure script is /etc/qemu-ifdown. Use script=no or downscript=no to disable script execution.
If running QEMU as an unprivileged user, use the network helper helper to configure the TAP interface and attach it to the bridge. The default network helper executable is /path/to/qemu-bridge-helper and the default bridge device is br0.
fd=h can be used to specify the handle of an already opened host TAP interface.
Examples:
#launch a QEMU instance with the default network script qemu-system-i386 linux.img -net nic -net tap
#launch a QEMU instance with two NICs, each one connected #to a TAP device qemu-system-i386 linux.img \ -net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \ -net nic,vlan=1 -net tap,vlan=1,ifname=tap1
#launch a QEMU instance with the default network helper to #connect a TAP device to bridge br0 qemu-system-i386 linux.img \ -net nic -net tap,"helper=/path/to/qemu-bridge-helper"
Connect a host TAP network interface to a host bridge device.
Use the network helper helper to configure the TAP interface and attach it to the bridge. The default network helper executable is /path/to/qemu-bridge-helper and the default bridge device is br0.
Examples:
#launch a QEMU instance with the default network helper to #connect a TAP device to bridge br0 qemu-system-i386 linux.img -net bridge -net nic,model=virtio
#launch a QEMU instance with the default network helper to #connect a TAP device to bridge qemubr0 qemu-system-i386 linux.img -net bridge,br=qemubr0 -net nic,model=virtio
Connect the VLAN n to a remote VLAN in another QEMU virtual machine using a TCP socket connection. If listen is specified, QEMU waits for incoming connections on port (host is optional). connect is used to connect to another QEMU instance using the listen option. fd=h specifies an already opened TCP socket.
Example:
# launch a first QEMU instance qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:56 \ -net socket,listen=:1234 # connect the VLAN 0 of this instance to the VLAN 0 # of the first instance qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:57 \ -net socket,connect=<IP_ADDRESS>:1234
Create a VLAN n shared with another QEMU virtual machines using a UDP multicast socket, effectively making a bus for every QEMU with same multicast address maddr and port. NOTES:
Example:
# launch one QEMU instance qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:56 \ -net socket,mcast=<IP_ADDRESS>:1234 # launch another QEMU instance on same "bus" qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:57 \ -net socket,mcast=<IP_ADDRESS>:1234 # launch yet another QEMU instance on same "bus" qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:58 \ -net socket,mcast=<IP_ADDRESS>:1234
Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected # is UML's default) qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:56 \ -net socket,mcast=<IP_ADDRESS>:1102 # launch UML /path/to/linux ubd0=/path/to/root_fs eth0=mcast
Example (send packets from host’s <IP_ADDRESS>):
qemu-system-i386 linux.img \ -net nic,macaddr=52:54:00:12:34:56 \ -net socket,mcast=<IP_ADDRESS>:1102,localaddr=<IP_ADDRESS>
Connect VLAN n to L2TPv3 pseudowire. L2TPv3 (RFC3391) is a popular protocol to transport Ethernet (and other Layer 2) data frames between two systems. It is present in routers, firewalls and the Linux kernel (from version 3.3 onwards).
This transport allows a VM to communicate to another VM, router or firewall directly.
source address (mandatory)
destination address (mandatory)
select udp encapsulation (default is ip).
source udp port.
destination udp port.
force v6, otherwise defaults to v4.
Cookies are a weak form of security in the l2tpv3 specification. Their function is mostly to prevent misconfiguration. By default they are 32 bit.
Set cookie size to 64 bit instead of the default 32
Force a ’cut-down’ L2TPv3 with no counter as in draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
Work around broken counter handling in peer. This may also help on networks which have packet reorder.
Add an extra offset between header and data
For example, to attach a VM running on host <IP_ADDRESS> via L2TPv3 to the bridge br-lan on the remote Linux host <IP_ADDRESS>:
# Setup tunnel on linux host using raw ip as encapsulation # on <IP_ADDRESS> ip l2tp add tunnel remote <IP_ADDRESS> local <IP_ADDRESS> tunnel_id 1 peer_tunnel_id 1 \ encap udp udp_sport 16384 udp_dport 16384 ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \ 0xFFFFFFFF peer_session_id 0xFFFFFFFF ifconfig vmtunnel0 mtu 1500 ifconfig vmtunnel0 up brctl addif br-lan vmtunnel0 # on <IP_ADDRESS> # launch QEMU instance - if your network has reorder or is very lossy add ,pincounter qemu-system-i386 linux.img -net nic -net l2tpv3,src=<IP_ADDRESS>,dst=<IP_ADDRESS>,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter
Connect VLAN n to PORT n of a vde switch running on host and listening for incoming connections on socketpath. Use GROUP groupname and MODE octalmode to change default ownership and permissions for communication port. This option is only available if QEMU has been compiled with vde support enabled.
Example:
# launch vde switch vde_switch -F -sock /tmp/myswitch # launch QEMU instance qemu-system-i386 linux.img -net nic -net vde,sock=/tmp/myswitch
Create a hub port on QEMU "vlan" hubid.
The hubport netdev lets you connect a NIC to a QEMU "vlan" instead of a single
netdev. -net
and -device
with parameter vlan create the
required hub automatically.
Establish a vhost-user netdev, backed by a chardev id. The chardev should be a unix domain socket backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement messages to an application on the other end of the socket. On non-MSIX guests, the feature can be forced with vhostforce. Use ’queues=n’ to specify the number of queues to be created for multiqueue vhost-user.
Example:
qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \ -numa node,memdev=mem \ -chardev socket,id=chr0,path=/path/to/socket \ -netdev type=vhost-user,id=net0,chardev=chr0 \ -device virtio-net-pci,netdev=net0
Dump network traffic on VLAN n to file file (qemu-vlan0.pcap by default). At most len bytes (64k by default) per packet are stored. The file format is libpcap, so it can be analyzed with tools such as tcpdump or Wireshark. Note: For devices created with ’-netdev’, use ’-object filter-dump,...’ instead.
Indicate that no network devices should be configured. It is used to override the default configuration (-net nic -net user) which is activated if no -net options are provided.
The general form of a character device option is:
Backend is one of: null, socket, udp, msmouse, vc, ringbuf, file, pipe, console, serial, pty, stdio, braille, tty, parallel, parport, spicevmc. spiceport. The specific backend will determine the applicable options.
Use "-chardev help" to print all available chardev backend types.
All devices must have an id, which can be any string up to 127 characters long. It is used to uniquely identify this device in other command line directives.
A character device may be used in multiplexing mode by multiple front-ends. Specify mux=on to enable this mode. A multiplexer is a "1:N" device, and here the "1" end is your specified chardev backend, and the "N" end is the various parts of QEMU that can talk to a chardev. If you create a chardev with id=myid and mux=on, QEMU will create a multiplexer with your specified ID, and you can then configure multiple front ends to use that chardev ID for their input/output. Up to four different front ends can be connected to a single multiplexed chardev. (Without multiplexing enabled, a chardev can only be used by a single front end.) For instance you could use this to allow a single stdio chardev to be used by two serial ports and the QEMU monitor:
-chardev stdio,mux=on,id=char0 \ -mon chardev=char0,mode=readline \ -serial chardev:char0 \ -serial chardev:char0
You can have more than one multiplexer in a system configuration; for instance you could have a TCP port multiplexed between UART 0 and UART 1, and stdio multiplexed between the QEMU monitor and a parallel port:
-chardev stdio,mux=on,id=char0 \ -mon chardev=char0,mode=readline \ -parallel chardev:char0 \ -chardev tcp,...,mux=on,id=char1 \ -serial chardev:char1 \ -serial chardev:char1
When you’re using a multiplexed character device, some escape sequences are interpreted in the input. See Keys in the character backend multiplexer.
Note that some other command line options may implicitly create multiplexed character backends; for instance -serial mon:stdio creates a multiplexed stdio backend connected to the serial port and the QEMU monitor, and -nographic also multiplexes the console and the monitor to stdio.
There is currently no support for multiplexing in the other direction (where a single QEMU front end takes input and output from multiple chardevs).
Every backend supports the logfile option, which supplies the path to a file to record all data transmitted via the backend. The logappend option controls whether the log file will be truncated or appended to when opened.
Further options to each backend are described below.
A void device. This device will not emit any data, and will drop any data it receives. The null backend does not take any options.
Create a two-way stream socket, which can be either a TCP or a unix socket. A unix socket will be created if path is specified. Behaviour is undefined if TCP options are specified for a unix socket.
server specifies that the socket shall be a listening socket.
nowait specifies that QEMU should not block waiting for a client to connect to a listening socket.
telnet specifies that traffic on the socket should interpret telnet escape sequences.
reconnect sets the timeout for reconnecting on non-server sockets when the remote end goes away. qemu will delay this many seconds and then attempt to reconnect. Zero disables reconnecting, and is the default.
tls-creds requests enablement of the TLS protocol for encryption, and specifies the id of the TLS credentials to use for the handshake. The credentials must be previously created with the -object tls-creds argument.
TCP and unix socket options are given below:
host for a listening socket specifies the local address to be bound.
For a connecting socket species the remote host to connect to. host is
optional for listening sockets. If not specified it defaults to <IP_ADDRESS>
.
port for a listening socket specifies the local port to be bound. For a connecting socket specifies the port on the remote host to connect to. port can be given as either a port number or a service name. port is required.
to is only relevant to listening sockets. If it is specified, and port cannot be bound, QEMU will attempt to bind to subsequent ports up to and including to until it succeeds. to must be specified as a port number.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If neither is specified the socket may use either protocol.
nodelay disables the Nagle algorithm.
path specifies the local path of the unix socket. path is required.
Sends all traffic from the guest to a remote host over UDP.
host specifies the remote host to connect to. If not specified it
defaults to localhost
.
port specifies the port on the remote host to connect to. port is required.
localaddr specifies the local address to bind to. If not specified it
defaults to <IP_ADDRESS>
.
localport specifies the local port to bind to. If not specified any available local port will be used.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If neither is specified the device may use either protocol.
Forward QEMU’s emulated msmouse events to the guest. msmouse does not take any options.
Connect to a QEMU text console. vc may optionally be given a specific size.
width and height specify the width and height respectively of the console, in pixels.
cols and rows specify that the console be sized to fit a text console with the given dimensions.
Create a ring buffer with fixed size size.
size must be a power of two and defaults to 64K
.
Log all traffic received from the guest to a file.
path specifies the path of the file to be opened. This file will be created if it does not already exist, and overwritten if it does. path is required.
Create a two-way connection to the guest. The behaviour differs slightly between Windows hosts and other hosts:
On Windows, a single duplex pipe will be created at \\.pipe\path.
On other hosts, 2 pipes will be created called path.in and path.out. Data written to path.in will be received by the guest. Data written by the guest can be read from path.out. QEMU will not create these fifos, and requires them to be present.
path forms part of the pipe path as described above. path is required.
Send traffic from the guest to QEMU’s standard output. console does not take any options.
console is only available on Windows hosts.
Send traffic from the guest to a serial device on the host.
On Unix hosts serial will actually accept any tty device, not only serial lines.
path specifies the name of the serial device to open.
Create a new pseudo-terminal on the host and connect to it. pty does not take any options.
pty is not available on Windows hosts.
Connect to standard input and standard output of the QEMU process.
signal controls if signals are enabled on the terminal, that includes exiting QEMU with the key sequence Control-c. This option is enabled by default, use signal=off to disable it.
Connect to a local BrlAPI server. braille does not take any options.
tty is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and DragonFlyBSD hosts. It is an alias for serial.
path specifies the path to the tty. path is required.
parallel is only available on Linux, FreeBSD and DragonFlyBSD hosts.
Connect to a local parallel port.
path specifies the path to the parallel port device. path is required.
spicevmc is only available when spice support is built in.
debug debug level for spicevmc
name name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
spiceport is only available when spice support is built in.
debug debug level for spicevmc
name name of spice port to connect to
Connect to a spice port, allowing a Spice client to handle the traffic identified by a name (preferably a fqdn).
In addition to using normal file images for the emulated storage devices, QEMU can also use networked resources such as iSCSI devices. These are specified using a special URL syntax.
iSCSI support allows QEMU to access iSCSI resources directly and use as images for the guest storage. Both disk and cdrom images are supported.
Syntax for specifying iSCSI LUNs is “iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>”
By default qemu will use the iSCSI initiator-name ’iqn.2008-11.org.linux-kvm[:<name>]’ but this can also be set from the command line or a configuration file.
Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to detect stalled requests and force a reestablishment of the session. The timeout is specified in seconds. The default is 0 which means no timeout. Libiscsi 1.15.0 or greater is required for this feature.
Example (without authentication):
qemu-system-i386 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \ -cdrom iscsi://<IP_ADDRESS>/iqn.2001-04.com.example/2 \ -drive file=iscsi://<IP_ADDRESS>/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
qemu-system-i386 -drive<EMAIL_ADDRESS>Example (CHAP username/password via environment variables):
LIBISCSI_CHAP_USERNAME="user" \ LIBISCSI_CHAP_PASSWORD="password" \ qemu-system-i386 -drive file=iscsi://<IP_ADDRESS>/iqn.2001-04.com.example/1
iSCSI support is an optional feature of QEMU and only available when compiled and linked against libiscsi.
iSCSI parameters such as username and password can also be specified via a configuration file. See qemu-doc for more information and examples.
QEMU supports NBD (Network Block Devices) both using TCP protocol as well as Unix Domain Sockets.
Syntax for specifying a NBD device using TCP “nbd:<server-ip>:<port>[:exportname=<export>]”
Syntax for specifying a NBD device using Unix Domain Sockets “nbd:unix:<domain-socket>[:exportname=<export>]”
Example for TCP
qemu-system-i386 --drive file=nbd:<IP_ADDRESS>:30000
Example for Unix Domain Sockets
qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket
QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
qemu-system-i386 -drive<EMAIL_ADDRESS>qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other authentication methods may be supported in future.
Sheepdog is a distributed storage system for QEMU. QEMU supports using either local sheepdog devices or remote networked devices.
Syntax for specifying a sheepdog device
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
Example
qemu-system-i386 --drive file=sheepdog://<IP_ADDRESS>:30000/MyVirtualMachine
See also https://sheepdog.github.io/sheepdog/.
GlusterFS is a user space distributed file system. QEMU supports the use of GlusterFS volumes for hosting VM disk images using TCP, Unix Domain Sockets and RDMA transport protocols.
Syntax for specifying a VM disk image on GlusterFS volume is
URI: gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...] JSON: 'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...", "server":[{"type":"tcp","host":"...","port":"..."}, {"type":"unix","socket":"..."}]}}'
Example
URI: qemu-system-x86_64 --drive file=gluster://<IP_ADDRESS>/testvol/a.img, file.debug=9,file.logfile=/var/log/qemu-gluster.log JSON: qemu-system-x86_64 'json:{"driver":"qcow2", "file":{"driver":"gluster", "volume":"testvol","path":"a.img", "debug":9,"logfile":"/var/log/qemu-gluster.log", "server":[{"type":"tcp","host":"<IP_ADDRESS>","port":24007}, {"type":"unix","socket":"/var/run/glusterd.socket"}]}}' qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img, file.debug=9,file.logfile=/var/log/qemu-gluster.log, file.server.0.type=tcp,file.server.0.host=<IP_ADDRESS>,file.server.0.port=24007, file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
See also http://www.gluster.org.
QEMU supports read-only access to files accessed over http(s) and ftp(s).
Syntax using a single filename:
<protocol>://[<username>[:<password>]@]<host>/<path>
where:
’http’, ’https’, ’ftp’, or ’ftps’.
Optional username for authentication to the remote server.
Optional password for authentication to the remote server.
Address of the remote server.
Path on the remote server, including any query string.
The following options are also supported:
The full URL when passing options to the driver explicitly.
The amount of data to read ahead with each range request to the remote server. This value may optionally have the suffix ’T’, ’G’, ’M’, ’K’, ’k’ or ’b’. If it does not have a suffix, it will be assumed to be in bytes. The value must be a multiple of 512 bytes. It defaults to 256k.
Whether to verify the remote server’s certificate when connecting over SSL. It can have the value ’on’ or ’off’. It defaults to ’on’.
Send this cookie (it can also be a list of cookies separated by ’;’) with each outgoing request. Only supported when using protocols such as HTTP which support cookies, otherwise ignored.
Set the timeout in seconds of the CURL connection. This timeout is the time that CURL waits for a response from the remote server to get the size of the image to be downloaded. If not set, the default timeout of 5 seconds is used.
Note that when passing options to qemu explicitly, driver is the value of <protocol>.
Example: boot from a remote Fedora 20 live ISO image
qemu-system-x86_64 --drive media=cdrom,file=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local overlay for writes, copy-on-read, and a readahead of 64k
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"https://dl.fedoraproject.org/pub/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2 qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server with a self-signed certificate using a local overlay for writes, a readahead of 64k and a timeout of 10 seconds.
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2 qemu-system-x86_64 -drive file=/tmp/test.qcow2
Defines the function of the corresponding Bluetooth HCI. -bt options
are matched with the HCIs present in the chosen machine type. For
example when emulating a machine with only one HCI built into it, only
the first -bt hci[...]
option is valid and defines the HCI’s
logic. The Transport Layer is decided by the machine type. Currently
the machines n800
and n810
have one HCI and all other
machines have none.
The following three types are recognized:
(default) The corresponding Bluetooth HCI assumes no internal logic and will not respond to any HCI commands or emit events.
(bluez
only) The corresponding HCI passes commands / events
to / from the physical HCI identified by the name id (default:
hci0
) on the computer running QEMU. Only available on bluez
capable systems like Linux.
Add a virtual, standard HCI that will participate in the Bluetooth
scatternet n (default 0
). Similarly to -net
VLANs, devices inside a bluetooth network n can only communicate
with other devices in the same network (scatternet).
(Linux-host only) Create a HCI in scatternet n (default 0) attached
to the host bluetooth stack instead of to the emulated target. This
allows the host and target machines to participate in a common scatternet
and communicate. Requires the Linux vhci
driver installed. Can
be used as following:
qemu-system-i386 [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5
Emulate a bluetooth device dev and place it in network n
(default 0
). QEMU can only emulate one type of bluetooth devices
currently:
Virtual wireless keyboard implementing the HIDP bluetooth profile.
The general form of a TPM device option is:
Backend type must be: passthrough.
The specific backend type will determine the applicable options.
The -tpmdev
option creates the TPM backend and requires a
-device
option that specifies the TPM frontend interface model.
Options to each backend are described below.
Use ’help’ to print all available TPM backend types.
qemu -tpmdev help
(Linux-host only) Enable access to the host’s TPM using the passthrough driver.
path specifies the path to the host’s TPM device, i.e., on
a Linux host this would be /dev/tpm0
.
path is optional and by default /dev/tpm0
is used.
cancel-path specifies the path to the host TPM device’s sysfs entry allowing for cancellation of an ongoing TPM command. cancel-path is optional and by default QEMU will search for the sysfs entry to use.
Some notes about using the host’s TPM with the passthrough driver:
The TPM device accessed by the passthrough driver must not be used by any other application on the host.
Since the host’s firmware (BIOS/UEFI) has already initialized the TPM, the VM’s firmware (BIOS/UEFI) will not be able to initialize the TPM again and may therefore not show a TPM-specific menu that would otherwise allow the user to configure the TPM, e.g., allow the user to enable/disable or activate/deactivate the TPM. Further, if TPM ownership is released from within a VM then the host’s TPM will get disabled and deactivated. To enable and activate the TPM again afterwards, the host has to be rebooted and the user is required to enter the firmware’s menu to enable and activate the TPM. If the TPM is left disabled and/or deactivated most TPM commands will fail.
To create a passthrough TPM use the following two options:
-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
Note that the -tpmdev
id is tpm0
and is referenced by
tpmdev=tpm0
in the device option.
When using these options, you can use a given Linux or Multiboot kernel without installing it in the disk image. It can be useful for easier testing of various kernels.
Use bzImage as kernel image. The kernel can be either a Linux kernel or in multiboot format.
Use cmdline as kernel command line
Use file as initial ram disk.
This syntax is only available with multiboot.
Use file1 and file2 as modules and pass arg=foo as parameter to the first module.
Use file as a device tree binary (dtb) image and pass it to the kernel on boot.
Add named fw_cfg entry with contents from file file.
Add named fw_cfg entry with contents from string str.
The terminating NUL character of the contents of str will not be included as part of the fw_cfg item data. To insert contents with embedded NUL characters, you have to use the file parameter.
The fw_cfg entries are passed by QEMU through to the guest.
Example:
-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
creates an fw_cfg entry named opt/com.mycompany/blob with contents from ./my_blob.bin.
Redirect the virtual serial port to host character device
dev. The default device is vc
in graphical mode and
stdio
in non graphical mode.
This option can be used several times to simulate up to 4 serial ports.
Use -serial none
to disable all serial ports.
Available character devices are:
Virtual console. Optionally, a width and height can be given in pixel with
vc:800x600
It is also possible to specify width or height in characters:
vc:80Cx24C
[Linux only] Pseudo TTY (a new PTY is automatically allocated)
No device is allocated.
void device
Use a named character device defined with the -chardev
option.
[Linux only] Use host tty, e.g. /dev/ttyS0. The host serial port parameters are set according to the emulated ones.
[Linux only, parallel port only] Use host parallel port N. Currently SPP and EPP parallel port features can be used.
Write output to filename. No character can be read.
[Unix only] standard input/output
name pipe filename
[Windows only] Use host serial port n
This implements UDP Net Console.
When remote_host or src_ip are not specified
they default to <IP_ADDRESS>
.
When not using a specified src_port a random port is automatically chosen.
If you just want a simple readonly console you can use netcat
or
nc
, by starting QEMU with: -serial udp::4555
and nc as:
nc -u -l -p 4555
. Any time QEMU writes something to that port it
will appear in the netconsole session.
If you plan to send characters back via netconsole or you want to stop
and start QEMU a lot of times, you should have QEMU use the same
source port each time by using something like -serial
udp::4555@:4556
to QEMU. Another approach is to use a patched
version of netcat which can listen to a TCP port and send and receive
characters via udp. If you have a patched version of netcat which
activates telnet remote echo and single char transfer, then you can
use the following options to set up a netcat redirector to allow
telnet on port 5555 to access the QEMU port.
QEMU Options:
-serial udp::4555@:4556
netcat options:
-u -P 4555 -L <IP_ADDRESS>:4556 -t -p 5555 -I -T
telnet options:
localhost 5555
The TCP Net Console has two modes of operation. It can send the serial
I/O to a location or wait for a connection from a location. By default
the TCP Net Console is sent to host at the port. If you use
the server option QEMU will wait for a client socket application
to connect to the port before continuing, unless the nowait
option was specified. The nodelay
option disables the Nagle buffering
algorithm. The reconnect
option only applies if noserver is
set, if the connection goes down it will attempt to reconnect at the
given interval. If host is omitted, <IP_ADDRESS> is assumed. Only
one TCP connection at a time is accepted. You can use telnet
to
connect to the corresponding character device.
Example to send tcp console to <IP_ADDRESS> port 4444
-serial tcp:<IP_ADDRESS>:4444
Example to listen and wait on port 4444 for connection
-serial tcp::4444,server
Example to not wait and listen on ip <IP_ADDRESS> port 4444
-serial tcp:<IP_ADDRESS>:4444,server,nowait
The telnet protocol is used instead of raw tcp sockets. The options
work the same as if you had specified -serial tcp
. The
difference is that the port acts like a telnet server or client using
telnet option negotiation. This will also allow you to send the
MAGIC_SYSRQ sequence if you use a telnet that supports sending the break
sequence. Typically in unix telnet you do it with Control-] and then
type "send break" followed by pressing the enter key.
A unix domain socket is used instead of a tcp socket. The option works the
same as if you had specified -serial tcp
except the unix domain socket
path is used for connections.
This is a special option to allow the monitor to be multiplexed onto another serial port. The monitor is accessed with key sequence of Control-a and then pressing c. dev_string should be any one of the serial devices specified above. An example to multiplex the monitor onto a telnet server listening on port 4444 would be:
-serial mon:telnet::4444,server,nowait
When the monitor is multiplexed to stdio in this way, Ctrl+C will not terminate QEMU any more but will be passed to the guest instead.
Braille device. This will use BrlAPI to display the braille output on a real or fake device.
Three button serial mouse. Configure the guest to use Microsoft protocol.
Redirect the virtual parallel port to host device dev (same devices as the serial port). On Linux hosts, /dev/parportN can be used to use hardware devices connected on the corresponding host parallel port.
This option can be used several times to simulate up to 3 parallel ports.
Use -parallel none
to disable all parallel ports.
Redirect the monitor to host device dev (same devices as the
serial port).
The default device is vc
in graphical mode and stdio
in
non graphical mode.
Use -monitor none
to disable the default monitor.
Like -monitor but opens in ’control’ mode.
Like -qmp but uses pretty JSON formatting.
Setup monitor on chardev name.
Redirect the debug console to host device dev (same devices as the
serial port). The debug console is an I/O port which is typically port
0xe9; writing to that I/O port sends output to this device.
The default device is vc
in graphical mode and stdio
in
non graphical mode.
Store the QEMU process PID in file. It is useful if you launch QEMU from a script.
Run the emulation in single step mode.
Do not start CPU at startup (you must type ’c’ in the monitor).
Run qemu with realtime features. mlocking qemu and guest memory can be enabled via mlock=on (enabled by default).
Wait for gdb connection on device dev (see gdb_usage). Typical connections will likely be TCP-based, but also UDP, pseudo TTY, or even stdio are reasonable use case. The latter is allowing to start QEMU from within gdb and establish the connection via a pipe:
(gdb) target remote | exec qemu-system-i386 -gdb stdio ...
Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port 1234 (see gdb_usage).
Enable logging of specified items. Use ’-d help’ for a list of log items.
Output log in logfile instead of to stderr
Filter debug output to that relevant to a range of target addresses. The filter spec can be either start+size, start-size or start..end where start end and size are the addresses and sizes required. For example:
-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
Will dump output for any code in the 0x1000 sized block starting at 0x8000 and the 0x200 sized block starting at 0xffffffc000080000 and another 0x1000 sized block starting at 0xffffffc00005f000.
Set the directory for the BIOS, VGA BIOS and keymaps.
To list all the data directories, use -L help
.
Set the filename for the BIOS.
Enable KVM full virtualization support. This option is only available if KVM support is enabled when compiling.
Enable HAX (Hardware-based Acceleration eXecution) support. This option is only available if HAX support is enabled when compiling. HAX is only applicable to MAC and Windows platform, and thus does not conflict with KVM.
Specify xen guest domain id (XEN only).
Create domain using xen hypercalls, bypassing xend. Warning: should not be used when xend is in use (XEN only).
Attach to existing xen domain. xend will use this when starting QEMU (XEN only). Restrict set of available xen operations to specified domain id (XEN only).
Exit instead of rebooting.
Don’t exit QEMU on guest shutdown, but instead only stop the emulation. This allows for instance switching to monitor to commit changes to the disk image.
Start right away with a saved state (loadvm
in monitor)
Daemonize the QEMU process after initialization. QEMU will not detach from standard IO until it is ready to receive connections on any of its devices. This option is a useful way for external programs to launch QEMU without having to cope with initialization race conditions.
Load the contents of file as an option ROM.
Specify base as utc
or localtime
to let the RTC start at the current
UTC or local time, respectively. localtime
is required for correct date in
MS-DOS or Windows. To start at a specific point in time, provide date in the
format 2006-06-17T16:01:21
or 2006-06-17
. The default base is UTC.
By default the RTC is driven by the host system time. This allows using of the
RTC as accurate reference clock inside the guest, specifically if the host
time is smoothly following an accurate external reference clock, e.g. via NTP.
If you want to isolate the guest time from the host, you can set clock
to rt
instead. To even prevent it from progressing during suspension,
you can set it to vm
.
Enable driftfix (i386 targets only) if you experience time drift problems, specifically with Windows’ ACPI HAL. This option will try to figure out how many timer interrupts were not processed by the Windows guest and will re-inject them.
Enable virtual instruction counter. The virtual cpu will execute one
instruction every 2^N ns of virtual time. If auto
is specified
then the virtual cpu speed will be automatically adjusted to keep virtual
time within a few seconds of real time.
When the virtual cpu is sleeping, the virtual time will advance at default speed unless sleep=on|off is specified. With sleep=on|off, the virtual time will jump to the next timer deadline instantly whenever the virtual cpu goes to sleep mode and will not advance if no timer is enabled. This behavior give deterministic execution times from the guest point of view.
Note that while this option can give deterministic behavior, it does not provide cycle accurate emulation. Modern CPUs contain superscalar out of order cores with complex cache hierarchies. The number of instructions executed often has little or no correlation with actual performance.
align=on will activate the delay algorithm which will try
to synchronise the host clock and the virtual clock. The goal is to
have a guest running at the real frequency imposed by the shift option.
Whenever the guest clock is behind the host clock and if
align=on is specified then we print a message to the user
to inform about the delay.
Currently this option does not work when shift is auto
.
Note: The sync algorithm will work for those shift values for which
the guest clock runs ahead of the host clock. Typically this happens
when the shift value is high (how high depends on the host machine).
When rr option is specified deterministic record/replay is enabled. Replay log is written into filename file in record mode and read from this file in replay mode.
Option rrsnapshot is used to create new vm snapshot named snapshot at the start of execution recording. In replay mode this option is used to load the initial VM state.
Create a virtual hardware watchdog device. Once enabled (by a guest action), the watchdog must be periodically polled by an agent inside the guest or else the guest will be restarted. Choose a model for which your guest has drivers.
The model is the model of hardware watchdog to emulate. Use
-watchdog help
to list available hardware models. Only one
watchdog can be enabled for a guest.
The following models may be available:
iBASE 700 is a very simple ISA watchdog with a single timer.
Intel 6300ESB I/O controller hub is a much more featureful PCI-based dual-timer watchdog.
A virtual watchdog for s390x backed by the diagnose 288 hypercall (currently KVM only).
The action controls what QEMU will do when the watchdog timer
expires.
The default is
reset
(forcefully reset the guest).
Other possible actions are:
shutdown
(attempt to gracefully shutdown the guest),
poweroff
(forcefully poweroff the guest),
pause
(pause the guest),
debug
(print a debug message and continue), or
none
(do nothing).
Note that the shutdown
action requires that the guest responds
to ACPI signals, which it may not be able to do in the sort of
situations where the watchdog would have expired, and thus
-watchdog-action shutdown
is not recommended for production use.
Examples:
-watchdog i6300esb -watchdog-action pause
-watchdog ib700
Change the escape character used for switching to the monitor when using
monitor and serial sharing. The default is 0x01
when using the
-nographic
option. 0x01
is equal to pressing
Control-a
. You can select a different character from the ascii
control keys where 1 through 26 map to Control-a through Control-z. For
instance you could use the either of the following to change the escape
character to Control-t.
-echr 0x14
-echr 20
Set virtio console.
This option is maintained for backward compatibility.
Please use -device virtconsole
for the new way of invocation.
Show cursor.
Set TB size.
Prepare for incoming migration, listen on a given tcp port.
Prepare for incoming migration, listen on a given unix socket.
Accept incoming migration from a given filedescriptor.
Accept incoming migration as an output from specified external command.
Wait for the URI to be specified via migrate_incoming. The monitor can be used to change settings (such as migration parameters) prior to issuing the migrate_incoming to allow the migration to begin.
Only allow migratable devices. Devices will not be allowed to enter an unmigratable state.
Don’t create default devices. Normally, QEMU sets the default devices like serial
port, parallel port, virtual console, monitor device, VGA adapter, floppy and
CD-ROM drive and others. The -nodefaults
option will disable all those
default devices.
Immediately before starting guest execution, chroot to the specified directory. Especially useful in combination with -runas.
Immediately before starting guest execution, drop root privileges, switching to the specified user.
Set OpenBIOS nvram variable to given value (PPC, SPARC only).
Enable semihosting mode (ARM, M68K, Xtensa, MIPS only).
Enable and configure semihosting (ARM, M68K, Xtensa, MIPS only).
native|gdb|auto
Defines where the semihosting calls will be addressed, to QEMU (native
)
or to GDB (gdb
). The default is auto
, which means gdb
during debug sessions and native
otherwise.
Allows the user to pass input arguments, and can be used multiple times to build
up a list. The old-style -kernel
/-append
method of passing a
command line is still supported for backward compatibility. If both the
--semihosting-config arg
and the -kernel
/-append
are
specified, the former is passed to semihosting as it always takes precedence.
Old param mode (ARM only).
Enable Seccomp mode 2 system call filter. ’on’ will enable syscall filtering and ’off’ will disable it. The default is ’off’.
Read device configuration from file. This approach is useful when you want to spawn QEMU process with many command line options but you don’t want to exceed the command line character limit.
Write device configuration to file. The file can be either filename to save
command line and device configuration into file or dash -
) character to print the
output to stdout. This can be later used as input file for -readconfig
option.
Normally QEMU loads configuration files from sysconfdir and datadir at startup.
The -nodefconfig
option will prevent QEMU from loading any of those config files.
The -no-user-config
option makes QEMU not load any of the user-provided
config files on sysconfdir, but won’t make it skip the QEMU-provided config
files from datadir.
Specify tracing options.
Immediately enable events matching pattern. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify multiple events or patterns, specify the -trace option multiple times.
Use -trace help
to print a list of names of trace points.
Immediately enable events listed in file. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend.
Log output traces to file. This option is only available if QEMU has been compiled with the simple tracing backend.
Enable FIPS 140-2 compliance mode.
prepend a timestamp to each log message.(default:on)
Dump json-encoded vmstate information for current machine type to file in file
Create a new object of type typename setting properties in the order they are specified. Note that the ’id’ property must be set. These objects are placed in the ’/objects’ path.
Creates a memory file backend object, which can be used to back the guest RAM with huge pages. The id parameter is a unique ID that will be used to reference this memory region when configuring the -numa argument. The size option provides the size of the memory region, and accepts common suffixes, eg 500M. The mem-path provides the path to either a shared memory or huge page filesystem mount. The share boolean option determines whether the memory region is marked as private to QEMU, or shared. The latter allows a co-operating external process to access the QEMU memory region.
Creates a random number generator backend which obtains entropy from a device on the host. The id parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. The filename parameter specifies which file to obtain entropy from and if omitted defaults to /dev/random.
Creates a random number generator backend which obtains entropy from an external daemon running on the host. The id parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. The chardev parameter is the unique ID of a character device backend that provides the connection to the RNG daemon.
Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depending on whether the QEMU network backend that uses the credentials will be acting as a client or as a server. If verify-peer is enabled (the default) then once the handshake is completed, the peer credentials will be verified, though this is a no-op for anonymous credentials.
The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will generate a set of DH parameters at startup. This is a computationally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated upfront and saved.
Creates a TLS anonymous credentials object, which can be used to provide TLS support on network backends. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depending on whether the QEMU network backend that uses the credentials will be acting as a client or as a server. If verify-peer is enabled (the default) then once the handshake is completed, the peer credentials will be verified. With x509 certificates, this implies that the clients must be provided with valid client certificates too.
The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS server. If the file is missing, QEMU will generate a set of DH parameters at startup. This is a computationally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated upfront and saved.
For x509 certificate credentials the directory will contain further files providing the x509 certificates. The certificates must be stored in PEM format, in filenames ca-cert.pem, ca-crl.pem (optional), server-cert.pem (only servers), server-key.pem (only servers), client-cert.pem (only clients), and client-key.pem (only clients).
For the server-key.pem and client-key.pem files which
contain sensitive private keys, it is possible to use an encrypted
version by providing the passwordid parameter. This provides
the ID of a previously created secret
object containing the
password for decryption.
Interval t can’t be 0, this filter batches the packet delivery: all packets arriving in a given interval on netdev netdevid are delayed until the end of the interval. Interval is in microseconds. status is optional that indicate whether the netfilter is on (enabled) or off (disabled), the default status for netfilter will be ’on’.
queue all|rx|tx is an option that can be applied to any netfilter.
all: the filter is attached both to the receive and the transmit queue of the netdev (default).
rx: the filter is attached to the receive queue of the netdev, where it will receive packets sent to the netdev.
tx: the filter is attached to the transmit queue of the netdev, where it will receive packets sent by the netdev.
filter-mirror on netdev netdevid,mirror net packet to chardevchardevid, if it has the vnet_hdr_support flag, filter-mirror will mirror packet with vnet_hdr_len.
filter-redirector on netdev netdevid,redirect filter’s net packet to chardev chardevid,and redirect indev’s packet to filter.if it has the vnet_hdr_support flag, filter-redirector will redirect packet with vnet_hdr_len. Create a filter-redirector we need to differ outdev id from indev id, id can not be the same. we can just use indev or outdev, but at least one of indev or outdev need to be specified.
Filter-rewriter is a part of COLO project.It will rewrite tcp packet to secondary from primary to keep secondary tcp connection,and rewrite tcp packet to primary from secondary make tcp packet can be handled by client.if it has the vnet_hdr_support flag, we can parse packet with vnet header.
usage: colo secondary: -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object filter-rewriter,id=rew0,netdev=hn0,queue=all
Dump the network traffic on netdev dev to the file specified by filename. At most len bytes (64k by default) per packet are stored. The file format is libpcap, so it can be analyzed with tools such as tcpdump or Wireshark.
Colo-compare gets packet from primary_inchardevid and secondary_inchardevid, than compare primary packet with secondary packet. If the packets are same, we will output primary packet to outdevchardevid, else we will notify colo-frame do checkpoint and send primary packet to outdevchardevid. if it has the vnet_hdr_support flag, colo compare will send/recv packet with vnet_hdr_len.
we must use it with the help of filter-mirror and filter-redirector.
primary: -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=mirror0,host=<IP_ADDRESS>,port=9003,server,nowait -chardev socket,id=compare1,host=<IP_ADDRESS>,port=9004,server,nowait -chardev socket,id=compare0,host=<IP_ADDRESS>,port=9001,server,nowait -chardev socket,id=compare0-0,host=<IP_ADDRESS>,port=9001 -chardev socket,id=compare_out,host=<IP_ADDRESS>,port=9005,server,nowait -chardev socket,id=compare_out0,host=<IP_ADDRESS>,port=9005 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0 secondary: -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown -device e1000,netdev=hn0,mac=52:a4:00:12:78:66 -chardev socket,id=red0,host=<IP_ADDRESS>,port=9003 -chardev socket,id=red1,host=<IP_ADDRESS>,port=9004 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
If you want to know the detail of above command line, you can read the colo-compare git log.
Creates a cryptodev backend which executes crypto opreation from the QEMU cipher APIS. The id parameter is a unique ID that will be used to reference this cryptodev backend from the virtio-crypto device. The queues parameter is optional, which specify the queue number of cryptodev backend, the default of queues is 1.
# qemu-system-x86_64 \ [...] \ -object cryptodev-backend-builtin,id=cryptodev0 \ -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \ [...]
Defines a secret to store a password, encryption key, or some other sensitive data. The sensitive data can either be passed directly via the data parameter, or indirectly via the file parameter. Using the data parameter is insecure unless the sensitive data is encrypted.
The sensitive data can be provided in raw format (the default), or base64. When encoded as JSON, the raw format only supports valid UTF-8 characters, so base64 is recommended for sending binary data. QEMU will convert from which ever format is provided to the format it needs internally. eg, an RBD password can be provided in raw format, even though it will be base64 encoded when passed onto the RBD sever.
For added protection, it is possible to encrypt the data associated with a secret using the AES-256-CBC cipher. Use of encryption is indicated by providing the keyid and iv parameters. The keyid parameter provides the ID of a previously defined secret that contains the AES-256 decryption key. This key should be 32-bytes long and be base64 encoded. The iv parameter provides the random initialization vector used for encryption of this particular secret and should be a base64 encrypted string of the 16-byte IV.
The simplest (insecure) usage is to provide the secret inline
# $QEMU -object secret,id=sec0,data=letmein,format=raw
The simplest secure usage is to provide the secret via a file
# printf "letmein" > mypasswd.txt # $QEMU -object secret,id=sec0,file=mypasswd.txt,format=raw
For greater security, AES-256-CBC should be used. To illustrate usage, consider the openssl command line tool which can encrypt the data. Note that when encrypting, the plaintext must be padded to the cipher block size (32 bytes) using the standard PKCS#5/6 compatible padding algorithm.
First a master key needs to be created in base64 encoding:
# openssl rand -base64 32 > key.b64 # KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"')
Each secret to be encrypted needs to have a random initialization vector generated. These do not need to be kept secret
# openssl rand -base64 16 > iv.b64 # IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"')
The secret to be defined can now be encrypted, in this case we’re telling openssl to base64 encode the result, but it could be left as raw bytes if desired.
# SECRET=$(printf "letmein" | openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
When launching QEMU, create a master secret pointing to key.b64
and specify that to be used to decrypt the user password. Pass the
contents of iv.b64
to the second secret
# $QEMU \ -object secret,id=secmaster0,format=base64,file=key.b64 \ -object secret,id=sec0,keyid=secmaster0,format=base64,\ data=$SECRET,iv=$(<iv.b64)
During the graphical emulation, you can use special key combinations to change
modes. The default key mappings are shown below, but if you use -alt-grab
then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt) and if you use
-ctrl-grab
then the modifier is the right Ctrl key (instead of Ctrl-Alt):
Toggle full screen
Enlarge the screen
Shrink the screen
Restore the screen’s un-scaled dimensions
Switch to virtual console ’n’. Standard console mappings are:
Target system display
Monitor
Serial port
Toggle mouse and keyboard grab.
In the virtual consoles, you can use Ctrl-Up, Ctrl-Down, Ctrl-PageUp and Ctrl-PageDown to move in the back log.
During emulation, if you are using a character backend multiplexer (which is the default if you are using -nographic) then several commands are available via an escape sequence. These key sequences all start with an escape character, which is Ctrl-a by default, but can be changed with -echr. The list below assumes you’re using the default.
Print this help
Exit emulator
Save disk data back to file (if -snapshot)
Toggle console timestamps
Send break (magic sysrq in Linux)
Rotate between the frontends connected to the multiplexer (usually this switches between the monitor and the console)
Send the escape character to the frontend
The QEMU monitor is used to give complex commands to the QEMU emulator. You can use it to:
The following commands are available:
Show the help for all commands or just for command cmd.
Commit changes to the disk images (if -snapshot is used) or backing files. If the backing file is smaller than the snapshot, then the backing file will be resized to be the same size as the snapshot. If the snapshot is smaller than the backing file, the backing file will not be truncated. If you want the backing file to match the size of the smaller snapshot, you can safely truncate it yourself once the commit operation successfully completes.
Quit the emulator.
Resize a block image while a guest is running. Usually requires guest action to see the updated size. Resize to a lower size is supported, but should be used with extreme caution. Note that this command only resizes image files, it can not resize block devices like LVM volumes.
Copy data from a backing file into a block device.
Set maximum speed for a background block operation.
Stop an active background block operation (streaming, mirroring).
Manually trigger completion of an active background block operation. For mirroring, this will switch the device to the destination path.
Pause an active block streaming operation.
Resume a paused block streaming operation.
Eject a removable medium (use -f to force it).
Remove host block device. The result is that guest generated IO is no longer submitted against the host device underlying the disk. Once a drive has been deleted, the QEMU Block layer returns -EIO which results in IO errors in the guest for applications that are reading/writing to the device. These errors are always reported to the guest, regardless of the drive’s error actions (drive options rerror, werror).
Change the configuration of a device.
Change the medium for a removable disk device to point to filename. eg
(qemu) change ide1-cd0 /path/to/some.iso
format is optional.
read-only-mode may be used to change the read-only status of the device. It accepts the following values:
Retains the current status; this is the default.
Makes the device read-only.
Makes the device writable.
Change the configuration of the VNC server. The valid syntax for display and options are described at sec_invocation. eg
(qemu) change vnc localhost:1
Change the password associated with the VNC server. If the new password is not supplied, the monitor will prompt for it to be entered. VNC passwords are only significant up to 8 letters. eg
(qemu) change vnc password Password: ********
Save screen into PPM image filename.
Output logs to filename.
changes status of a trace event
Open, close, or flush the trace file. If no argument is given, the status of the trace file is displayed.
Activate logging of the specified items.
Create a snapshot of the whole virtual machine. If tag is provided, it is used as human readable identifier. If there is already a snapshot with the same tag or ID, it is replaced. More info at vm_snapshots.
Set the whole virtual machine to the snapshot identified by the tag tag or the unique snapshot ID id.
Delete the snapshot identified by tag or id.
Run the emulation in single step mode. If called with option off, the emulation returns to normal mode.
Stop emulation.
Resume emulation.
Wakeup guest from suspend.
Start gdbserver session (default port=1234)
Virtual memory dump starting at addr.
Physical memory dump starting at addr.
fmt is a format which tells the command how to format the data. Its syntax is: /{count}{format}{size}
is the number of items to be dumped.
can be x (hex), d (signed decimal), u (unsigned decimal), o (octal), c (char) or i (asm instruction).
can be b (8 bits), h (16 bits), w (32 bits) or g (64 bits). On x86,
h
or w
can be specified with the i
format to
respectively select 16 or 32 bit code instruction size.
Examples:
(qemu) x/10i $eip 0x90107063: ret 0x90107064: sti 0x90107065: lea 0x0(%esi,1),%esi 0x90107069: lea 0x0(%edi,1),%edi 0x90107070: ret 0x90107071: jmp 0x90107080 0x90107073: nop 0x90107074: nop 0x90107075: nop 0x90107076: nop
(qemu) xp/80hx 0xb8000 0x000b8000: 0x0b50 0x0b6c 0x0b65 0x0b78 0x0b38 0x0b36 0x0b2f 0x0b42 0x000b8010: 0x0b6f 0x0b63 0x0b68 0x0b73 0x0b20 0x0b56 0x0b47 0x0b41 0x000b8020: 0x0b42 0x0b69 0x0b6f 0x0b73 0x0b20 0x0b63 0x0b75 0x0b72 0x000b8030: 0x0b72 0x0b65 0x0b6e 0x0b74 0x0b2d 0x0b63 0x0b76 0x0b73 0x000b8040: 0x0b20 0x0b30 0x0b35 0x0b20 0x0b4e 0x0b6f 0x0b76 0x0b20 0x000b8050: 0x0b32 0x0b30 0x0b30 0x0b33 0x0720 0x0720 0x0720 0x0720 0x000b8060: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8070: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8080: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8090: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
Print the host virtual address at which the guest’s physical address addr is mapped.
Print the host physical address at which the guest’s physical address addr is mapped.
Print expression value. Only the format part of fmt is used.
Read I/O port.
Write to I/O port.
Send keys to the guest. keys could be the name of the
key or the raw value in hexadecimal format. Use -
to press
several keys simultaneously. Example:
sendkey ctrl-alt-f1
This command is useful to send keys that your graphical user interface
intercepts at low level, such as ctrl-alt-f1
in X Window.
Reset the system.
Power down the system (if supported).
Compute the checksum of a memory region.
Add the USB device devname. This command is deprecated, please
use device_add
instead. For details of available devices see
usb_devices
Remove the USB device devname from the QEMU virtual USB
hub. devname has the syntax bus.addr
. Use the monitor
command info usb
to see the devices you can remove. This
command is deprecated, please use device_del
instead.
Add device.
Remove device id. id may be a short ID or a QOM object path.
Set the default CPU.
Move the active mouse to the specified coordinates dx dy with optional scroll axis dz.
Change the active mouse button state val (1=L, 2=M, 4=R).
Set which mouse device receives events at given index, index can be obtained with
info mice
Capture audio into filename. Using sample rate frequency bits per sample bits and number of channels channels.
Defaults:
Stop capture with a given index, index can be obtained with
info capture
save to disk virtual memory dump starting at addr of size size.
save to disk physical memory dump starting at addr of size size.
Define new values for the boot device list. Those values will override
the values specified on the command line through the -boot
option.
The values that can be specified here depend on the machine type, but are
the same that can be specified in the -boot
command line option.
Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).
Write data to ring buffer character device device. data must be a UTF-8 string.
Read and print up to size bytes from ring buffer character device device. Certain non-printable characters are printed \uXXXX, where XXXX is the character code in hexadecimal. Character \ is printed \\. Bug: can screw up when the buffer contains invalid UTF-8 sequences, NUL characters, after the ring buffer lost data, and when reading stops because the size limit is reached.
Migrate to uri (using -d to not wait for completion). -b for migration with full copy of disk -i for migration with incremental copy of disk (base image is shared)
Cancel the current VM migration.
Continue an incoming migration using the uri (that has the same syntax as the -incoming option).
Set cache size to value (in bytes) for xbzrle migrations.
Set maximum speed to value (in bytes) for migrations.
Set maximum tolerated downtime (in seconds) for migration.
Enable/Disable the usage of a capability capability for migration.
Set the parameter parameter for migration.
Switch in-progress migration to postcopy mode. Ignored after the end of migration (or once already in postcopy).
Tell COLO that heartbeat is lost, a failover or takeover is needed.
Set migration information for remote display. This makes the server ask the client to automatically reconnect using the new parameters once migration finished successfully. Only implemented for SPICE.
Dump guest memory to protocol. The file can be processed with crash or gdb. Without -z|-l|-s, the dump format is ELF. -p: do paging to get guest’s memory mapping. -z: dump in kdump-compressed format, with zlib compression. -l: dump in kdump-compressed format, with lzo compression. -s: dump in kdump-compressed format, with snappy compression. filename: dump file name. begin: the starting physical address. It’s optional, and should be specified together with length. length: the memory size, in bytes. It’s optional, and should be specified together with begin.
Save guest storage keys to a file.
Enables or disables migration mode.
Snapshot device, using snapshot file as target if provided
Take an internal snapshot on device if it support
Delete an internal snapshot on device if it support
Start mirroring a block device’s writes to a new destination, using the specified target.
Start a point-in-time copy of a block device to a specificed target.
Add drive to PCI storage controller.
Inject PCIe AER error
Add host VLAN client. Deprecated, please use netdev_add
instead.
Remove host VLAN client. Deprecated, please use netdev_del
instead.
Add host network device.
Remove host network device.
Create QOM object.
Destroy QOM object.
Redirect TCP or UDP connections from host to guest (requires -net user).
Remove host-to-guest TCP or UDP redirection.
Request VM to change its memory allocation to value (in MB).
Switch link name on (i.e. up) or off (i.e. down).
Change watchdog action.
List all the matching rules in the access control list, and the default policy. There are currently two named access control lists, vnc.x509dname and vnc.username matching on the x509 client certificate distinguished name, and SASL username respectively.
allow|deny
Set the default access control list policy, used in the event that
none of the explicit rules match. The default policy at startup is
always deny
.
allow|deny
[index]Add a match rule to the access control list, allowing or denying access.
The match will normally be an exact username or x509 distinguished name,
but can optionally include wildcard globs. eg<EMAIL_ADDRESS>to
allow all users in the EXAMPLE.COM
kerberos realm. The match will
normally be appended to the end of the ACL, but can be inserted
earlier in the list if the optional index parameter is supplied.
Remove the specified match rule from the access control list.
Remove all matches from the access control list, and set the default
policy back to deny
.
Start an NBD server on the given host and/or port. If the -a option is included, all of the virtual machine’s block devices that have an inserted media on them are automatically exported; in this case, the -w option makes the devices writable too.
Export a block device through QEMU’s NBD server, which must be started
beforehand with nbd_server_start
. The -w option makes the
exported device writable too.
Stop the QEMU embedded NBD server.
Inject an MCE on the given CPU (x86 only).
If a file descriptor is passed alongside this command using the SCM_RIGHTS mechanism on unix sockets, it is stored using the name fdname for later use by other monitor commands.
Close the file descriptor previously assigned to fdname using the
getfd
command. This is only needed if the file descriptor was never
used by another monitor command.
Set the encrypted device device password to password
This command is now obsolete and will always return an error since 2.10
Change I/O throttle limits for a block drive to bps bps_rd bps_wr iops iops_rd iops_wr
Change spice/vnc password. Use zero to make the password stay valid forever. action-if-connected specifies what should happen in case a connection is established: fail makes the password change fail. disconnect changes the password and disconnects the client. keep changes the password and keeps the connection up. keep is the default.
Specify when a password for spice/vnc becomes invalid. expire-time accepts:
Invalidate password instantly.
Password stays valid forever.
Password stays valid for nsec seconds starting now.
Password is invalidated at the given time. nsec are the seconds passed since 1970, i.e. unix epoch.
chardev-add accepts the same parameters as the -chardev command line switch.
chardev-change accepts existing chardev id and then the same arguments as the -chardev command line switch (except for "id").
Removes the chardev id.
Send a break on the chardev id.
Executes a qemu-io command on the given block device.
Add CPU with id id
Print QOM properties of object at location path
Set QOM property property of object at location path to value value
Show various information about the system state.
Show the version of QEMU.
Show the network state.
Show the character devices.
Show info of one block device or all block devices.
Show block device statistics.
Show progress of ongoing block device operations.
Show the cpu registers.
Show local APIC state
Show io APIC state
Show infos for each CPU.
Show the command line history.
Show the interrupts statistics (if available).
Show i8259 (PIC) state.
Show PCI information.
Show virtual to physical memory mappings.
Show the active virtual memory mappings.
Show memory tree.
Show dynamic compiler info.
Show dynamic compiler opcode counters
Show KVM information.
Show NUMA information.
Show guest USB devices.
Show host USB devices.
Show profiling information.
Show capture information.
Show the currently saved VM snapshots.
Show the current VM status (running|paused).
Show which guest mouse is receiving events.
Show the vnc server status.
Show the spice server status.
Show the current VM name.
Show the current VM UUID.
Show CPU statistics.
Show user network stack connection states.
Show migration status.
Show current migration capabilities.
Show current migration parameters.
Show current migration xbzrle cache size.
Show balloon information.
Show device tree.
Show qdev device model list.
Show QOM composition tree.
Show roms.
Show available trace-events & their state.
Show the TPM device.
Show memory backends
Show memory devices.
Show iothread’s identifiers.
Show rocker switch.
Show rocker ports.
Show rocker OF-DPA flow tables.
Show rocker OF-DPA groups.
Display the value of a storage key (s390 only)
Display the values of the CMMA storage attributes for a range of pages (s390 only)
Display the latest dump status.
Dump all the ramblocks of the system.
Show information about hotpluggable CPUs
Show Virtual Machine Generation ID
The monitor understands integers expressions for every integer argument. You can use register names to get the value of specifics CPU registers by prefixing them with $.
QEMU supports many disk image formats, including growable disk images (their size increase as non empty sectors are written), compressed and encrypted disk images.
You can create a disk image with the command:
qemu-img create myimage.img mysize
where myimage.img is the disk image filename and mysize is its
size in kilobytes. You can add an M
suffix to give the size in
megabytes and a G
suffix for gigabytes.
See qemu_img_invocation for more information.
If you use the option -snapshot, all disk images are
considered as read only. When sectors in written, they are written in
a temporary file created in /tmp. You can however force the
write back to the raw disk images by using the commit
monitor
command (or C-a s in the serial console).
VM snapshots are snapshots of the complete virtual machine including
CPU state, RAM, device state and the content of all the writable
disks. In order to use VM snapshots, you must have at least one non
removable and writable block device using the qcow2
disk image
format. Normally this device is the first virtual hard drive.
Use the monitor command savevm
to create a new VM snapshot or
replace an existing one. A human readable name can be assigned to each
snapshot in addition to its numerical ID.
Use loadvm
to restore a VM snapshot and delvm
to remove
a VM snapshot. info snapshots
lists the available snapshots
with their associated information:
(qemu) info snapshots Snapshot devices: hda Snapshot list (from hda): ID TAG VM SIZE DATE VM CLOCK 1 start 41M 2006-08-06 12:38:02 00:00:14.954 2 40M 2006-08-06 12:43:29 00:00:18.633 3 msys 40M 2006-08-06 12:44:04 00:00:23.514
A VM snapshot is made of a VM state info (its size is shown in
info snapshots
) and a snapshot of every writable disk image.
The VM state info is stored in the first qcow2
non removable
and writable block device. The disk image snapshots are stored in
every disk image. The size of a snapshot in a disk image is difficult
to evaluate and is not shown by info snapshots
because the
associated disk sectors are shared among all the snapshots to save
disk space (otherwise each snapshot would need a full copy of all the
disk images).
When using the (unrelated) -snapshot
option
(disk_images_snapshot_mode), you can always make VM snapshots,
but they are deleted as soon as you exit QEMU.
VM snapshots currently have the following known limitations:
qemu-img
Invocationqemu-img
[standard options] command [command options]
qemu-img allows you to create, convert and modify images offline. It can handle all image formats supported by QEMU.
Warning: Never use qemu-img to modify images in use by a running virtual machine or any other process; this may destroy the image. Also, be aware that querying an image that is being modified by another process may encounter inconsistent state.
Standard options:
Display this help and exit
Display version information and exit
Specify tracing options.
Immediately enable events matching pattern. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify multiple events or patterns, specify the -trace option multiple times.
Use -trace help
to print a list of names of trace points.
Immediately enable events listed in file. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend.
Log output traces to file. This option is only available if QEMU has been compiled with the simple tracing backend.
The following commands are supported:
Command parameters:
is a disk image filename
is a QEMU user creatable object definition. See the qemu(1)
manual
page for a description of the object properties. The most common object
type is a secret
, which is used to supply passwords and/or encryption
keys.
Indicates that the source filename parameter is to be interpreted as a full option string, not a plain filename. This parameter is mutually exclusive with the -f parameter.
Indicates that the output_filename parameter(s) are to be interpreted as a full option string, not a plain filename. This parameter is mutually exclusive with the -O parameters. It is currently required to also use the -n parameter to skip image creation. This restriction may be relaxed in a future release.
is the disk image format. It is guessed automatically in most cases. See below for a description of the supported disk formats.
will enumerate information about backing files in a disk image chain. Refer below for further description.
is the disk image size in bytes. Optional suffixes k
or K
(kilobyte, 1024) M
(megabyte, 1024k) and G
(gigabyte, 1024M)
and T (terabyte, 1024G) are supported. b
is ignored.
is the destination disk image filename
is the destination format
is a comma separated list of format specific options in a
name=value format. Use -o ?
for an overview of the options supported
by the used format or see the format descriptions below for details.
is param used for internal snapshot, format is ’snapshot.id=[ID],snapshot.name=[NAME]’ or ’[ID_OR_NAME]’
is deprecated, use snapshot_param instead
indicates that target image must be compressed (qcow format only)