- /proc/[pid]
-
There is a numerical subdirectory for each running process; the
subdirectory is named by the process ID.
Each such subdirectory contains the following
pseudo-files and directories.
- /proc/[pid]/auxv (since 2.6.0-test7)
-
This contains the contents of the ELF interpreter information passed
to the process at exec time.
The format is one unsigned long ID
plus one unsigned long value for each entry.
The last entry contains two zeros.
See also
getauxval(3).
- /proc/[pid]/cgroup (since Linux 2.6.24)
-
This file describes control groups to which the process/task belongs.
For each cgroup hierarchy there is one entry containing
colon-separated fields of the form:
5:cpuacct,cpu,cpuset:/daemons
-
The colon-separated fields are, from left to right:
-
- 1.
-
hierarchy ID number
- 2.
-
set of subsystems bound to the hierarchy
- 3.
-
control group in the hierarchy to which the process belongs
-
This file is present only if the
CONFIG_CGROUPS
kernel configuration option is enabled.
- /proc/[pid]/clear_refs (since Linux 2.6.22)
-
This is a write-only file, writable only by owner of the process.
The following values may be written to the file:
-
- 1 (since Linux 2.6.22)
-
Reset the PG_Referenced and ACCESSED/YOUNG
bits for all the pages associated with the process.
(Before kernel 2.6.32, writing any nonzero value to this file
had this effect.)
- 2 (since Linux 2.6.32)
-
Reset the PG_Referenced and ACCESSED/YOUNG
bits for all anonymous pages associated with the process.
- 3 (since Linux 2.6.32)
-
Reset the PG_Referenced and ACCESSED/YOUNG
bits for all file-mapped pages associated with the process.
-
Clearing the PG_Referenced and ACCESSED/YOUNG bits provides a method
to measure approximately how much memory a process is using.
One first inspects the values in the "Referenced" fields
for the VMAs shown in
/proc/[pid]/smaps
to get an idea of the memory footprint of the
process.
One then clears the PG_Referenced and ACCESSED/YOUNG bits
and, after some measured time interval,
once again inspects the values in the "Referenced" fields
to get an idea of the change in memory footprint of the
process during the measured interval.
If one is interested only in inspecting the selected mapping types,
then the value 2 or 3 can be used instead of 1.
A further value can be written to affect a different bit:
-
- 4 (since Linux 3.11)
-
Clear the soft-dirty bit for all the pages associated with the process.
This is used (in conjunction with
/proc/[pid]/pagemap)
by the check-point restore system to discover which pages of a process
have been dirtied since the file
/proc/[pid]/clear_refs
was written to.
-
Writing any value to
/proc/[pid]/clear_refs
other than those listed above has no effect.
The
/proc/[pid]/clear_refs
file is present only if the
CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
- /proc/[pid]/cmdline
-
This read-only file holds the complete command line for the process,
unless the process is a zombie.
In the latter case, there is nothing in this file:
that is, a read on this file will return 0 characters.
The command-line arguments appear in this file as a set of
strings separated by null bytes ('\0'),
with a further null byte after the last string.
- /proc/[pid]/comm (since Linux 2.6.33)
-
This file exposes the process's
comm
value---that is, the command name associated with the process.
Different threads in the same process may have different
comm
values, accessible via
/proc/[pid]/task/[tid]/comm.
A thread may modify its
comm
value, or that of any of other thread in the same thread group (see
the discussion of
CLONE_THREAD
in
clone(2)),
by writing to the file
/proc/self/task/[tid]/comm.
Strings longer than
TASK_COMM_LEN
(16) characters are silently truncated.
This file provides a superset of the
prctl(2)
PR_SET_NAME
and
PR_GET_NAME
operations, and is employed by
pthread_setname_np(3)
when used to rename threads other than the caller.
- /proc/[pid]/coredump_filter (since kernel 2.6.23)
-
See
core(5).
- /proc/[pid]/cpuset (since kernel 2.6.12)
-
See
cpuset(7).
- /proc/[pid]/cwd
-
This is a symbolic link to the current working directory of the process.
To find out the current working directory of process 20,
for instance, you can do this:
$ cd /proc/20/cwd; /bin/pwd
Note that the
pwd
command is often a shell built-in, and might
not work properly.
In
bash(1),
you may use
pwd -P.
In a multithreaded process, the contents of this symbolic link
are not available if the main thread has already terminated
(typically by calling
pthread_exit(3)).
- /proc/[pid]/environ
-
This file contains the environment for the process.
The entries are separated by null bytes ('\0'),
and there may be a null byte at the end.
Thus, to print out the environment of process 1, you would do:
$ strings /proc/1/environ
- /proc/[pid]/exe
-
Under Linux 2.2 and later, this file is a symbolic link
containing the actual pathname of the executed command.
This symbolic link can be dereferenced normally; attempting to open
it will open the executable.
You can even type
/proc/[pid]/exe
to run another copy of the same executable as is being run by
process [pid].
In a multithreaded process, the contents of this symbolic link
are not available if the main thread has already terminated
(typically by calling
pthread_exit(3)).
Under Linux 2.0 and earlier,
/proc/[pid]/exe
is a pointer to the binary which was executed,
and appears as a symbolic link.
A
readlink(2)
call on this file under Linux 2.0 returns a string in the format:
[device]:inode
For example, [0301]:1502 would be inode 1502 on device major 03 (IDE,
MFM, etc. drives) minor 01 (first partition on the first drive).
find(1)
with the
-inum
option can be used to locate the file.
- /proc/[pid]/fd/
-
This is a subdirectory containing one entry for each file which the
process has open, named by its file descriptor, and which is a
symbolic link to the actual file.
Thus, 0 is standard input, 1 standard output, 2 standard error, and so on.
For file descriptors for pipes and sockets,
the entries will be symbolic links whose content is the
file type with the inode.
A
readlink(2)
call on this file returns a string in the format:
type:[inode]
For example,
socket:[2248868]
will be a socket and its inode is 2248868.
For sockets, that inode can be used to find more information
in one of the files under
/proc/net/.
For file descriptors that have no corresponding inode
(e.g., file descriptors produced by
epoll_create(2),
eventfd(2),
inotify_init(2),
signalfd(2),
and
timerfd(2)),
the entry will be a symbolic link with contents of the form
anon_inode:<file-type>
In some cases, the
file-type
is surrounded by square brackets.
For example, an epoll file descriptor will have a symbolic link
whose content is the string
anon_inode:[eventpoll].
In a multithreaded process, the contents of this directory
are not available if the main thread has already terminated
(typically by calling
pthread_exit(3)).
Programs that will take a filename as a command-line argument,
but will not take input from standard input if no argument is supplied,
or that write to a file named as a command-line argument,
but will not send their output to standard output
if no argument is supplied, can nevertheless be made to use
standard input or standard out using
/proc/[pid]/fd.
For example, assuming that
-i
is the flag designating an input file and
-o
is the flag designating an output file:
$ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...
and you have a working filter.
/proc/self/fd/N
is approximately the same as
/dev/fd/N
in some UNIX and UNIX-like systems.
Most Linux MAKEDEV scripts symbolically link
/dev/fd
to
/proc/self/fd,
in fact.
Most systems provide symbolic links
/dev/stdin,
/dev/stdout,
and
/dev/stderr,
which respectively link to the files
0,
1,
and
2
in
/proc/self/fd.
Thus the example command above could be written as:
$ foobar -i /dev/stdin -o /dev/stdout ...
- /proc/[pid]/fdinfo/ (since kernel 2.6.22)
-
This is a subdirectory containing one entry for each file which the
process has open, named by its file descriptor.
The contents of each file can be read to obtain information
about the corresponding file descriptor, for example:
$ cat /proc/12015/fdinfo/4
pos: 1000
flags: 01002002
The
pos
field is a decimal number showing the current file offset.
The
flags
field is an octal number that displays the
file access mode and file status flags (see
open(2)).
The files in this directory are readable only by the owner of the process.
- /proc/[pid]/io (since kernel 2.6.20)
-
This file contains I/O statistics for the process, for example:
# cat /proc/3828/io
rchar: 323934931
wchar: 323929600
syscr: 632687
syscw: 632675
read_bytes: 0
write_bytes: 323932160
cancelled_write_bytes: 0
The fields are as follows:
-
- rchar: characters read
-
The number of bytes which this task has caused to be read from storage.
This is simply the sum of bytes which this process passed to
read(2)
and similar system calls.
It includes things such as terminal I/O and
is unaffected by whether or not actual
physical disk I/O was required (the read might have been satisfied from
pagecache).
- wchar: characters written
-
The number of bytes which this task has caused, or shall cause to be written
to disk.
Similar caveats apply here as with
rchar.
- syscr: read syscalls
-
Attempt to count the number of read I/O operations---that is,
system calls such as
read(2)
and
pread(2).
- syscw: write syscalls
-
Attempt to count the number of write I/O operations---that is,
system calls such as
write(2)
and
pwrite(2).
- read_bytes: bytes read
-
Attempt to count the number of bytes which this process really did cause to
be fetched from the storage layer.
This is accurate for block-backed filesystems.
- write_bytes: bytes written
-
Attempt to count the number of bytes which this process caused to be sent to
the storage layer.
- cancelled_write_bytes:
-
The big inaccuracy here is truncate.
If a process writes 1MB to a file and then deletes the file,
it will in fact perform no writeout.
But it will have been accounted as having caused 1MB of write.
In other words: this field represents the number of bytes which this process
caused to not happen, by truncating pagecache.
A task can cause "negative" I/O too.
If this task truncates some dirty pagecache,
some I/O which another task has been accounted for
(in its
write_bytes)
will not be happening.
-
Note:
In the current implementation, things are a bit racy on 32-bit systems:
if process A reads process B's
/proc/[pid]/io
while process B is updating one of these 64-bit counters,
process A could see an intermediate result.
- /proc/[pid]/limits (since kernel 2.6.24)
-
This file displays the soft limit, hard limit, and units of measurement
for each of the process's resource limits (see
getrlimit(2)).
Up to and including Linux 2.6.35,
this file is protected to allow reading only by the real UID of the process.
Since Linux 2.6.36,
this file is readable by all users on the system.
- /proc/[pid]/map_files/ (since kernel 3.3)
-
This subdirectory contains entries corresponding to memory-mapped
files (see
mmap(2)).
Entries are named by memory region start and end
address pair (expressed as hexadecimal numbers),
and are symbolic links to the mapped files themselves.
Here is an example, with the output wrapped and reformatted to fit on an 80-column display:
$ ls -l /proc/self/map_files/
lr--------. 1 root root 64 Apr 16 21:31
3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
...
Although these entries are present for memory regions that were
mapped with the
MAP_FILE
flag, the way anonymous shared memory (regions created with the
MAP_ANON | MAP_SHARED
flags)
is implemented in Linux
means that such regions also appear on this directory.
Here is an example where the target file is the deleted
/dev/zero
one:
lrw-------. 1 root root 64 Apr 16 21:33
7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)
This directory appears only if the
CONFIG_CHECKPOINT_RESTORE
kernel configuration option is enabled.
- /proc/[pid]/maps
-
A file containing the currently mapped memory regions and their access
permissions.
See
mmap(2)
for some further information about memory mappings.
The format of the file is:
address perms offset dev inode pathname
00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon
00651000-00652000 r--p 00051000 08:02 173521 /usr/bin/dbus-daemon
00652000-00655000 rw-p 00052000 08:02 173521 /usr/bin/dbus-daemon
00e03000-00e24000 rw-p 00000000 00:00 0 [heap]
00e24000-011f7000 rw-p 00000000 00:00 0 [heap]
...
35b1800000-35b1820000 r-xp 00000000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a20000-35b1a21000 rw-p 00020000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a21000-35b1a22000 rw-p 00000000 00:00 0
35b1c00000-35b1dac000 r-xp 00000000 08:02 135870 /usr/lib64/libc-2.15.so
35b1dac000-35b1fac000 ---p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870 /usr/lib64/libc-2.15.so
...
f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0 [stack:986]
...
7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0 [stack]
7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0 [vdso]
The
address
field is the address space in the process that the mapping occupies.
The
perms
field is a set of permissions:
r = read
w = write
x = execute
s = shared
p = private (copy on write)
The
offset
field is the offset into the file/whatever;
dev
is the device
(major:minor);
inode
is the inode on that device.
0 indicates that no inode is associated with the memory region,
as would be the case with BSS (uninitialized data).
The
pathname
field will usually be the file that is backing the mapping.
For ELF files,
you can easily coordinate with the
offset
field by looking at the
Offset field in the ELF program headers
(readelf -l).
There are additional helpful pseudo-paths:
-
- [stack]
-
The initial process's (also known as the main thread's) stack.
- [stack:<tid>] (since Linux 3.4)
-
A thread's stack (where the
<tid>
is a thread ID).
It corresponds to the
/proc/[pid]/task/[tid]/
path.
- [vdso]
-
The virtual dynamically linked shared object.
- [heap]
-
The process's heap.
-
If the
pathname
field is blank,
this is an anonymous mapping as obtained via the
mmap(2)
function.
There is no easy way to coordinate this back to a process's source,
short of running it through
gdb(1),
strace(1),
or similar.
Under Linux 2.0, there is no field giving pathname.
- /proc/[pid]/mem
-
This file can be used to access the pages of a process's memory through
open(2),
read(2),
and
lseek(2).
- /proc/[pid]/mountinfo (since Linux 2.6.26)
-
This file contains information about mount points.
It contains lines of the form:
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
-
The numbers in parentheses are labels for the descriptions below:
-
- (1)
-
mount ID: unique identifier of the mount (may be reused after
umount(2)).
- (2)
-
parent ID: ID of parent mount (or of self for the top of the mount tree).
- (3)
-
major:minor: value of
st_dev
for files on filesystem (see
stat(2)).
- (4)
-
root: root of the mount within the filesystem.
- (5)
-
mount point: mount point relative to the process's root.
- (6)
-
mount options: per-mount options.
- (7)
-
optional fields: zero or more fields of the form "tag[:value]".
- (8)
-
separator: marks the end of the optional fields.
- (9)
-
filesystem type: name of filesystem in the form "type[.subtype]".
- (10)
-
mount source: filesystem-specific information or "none".
- (11)
-
super options: per-superblock options.
-
Parsers should ignore all unrecognized optional fields.
Currently the possible optional fields are:
-
- shared:X
-
mount is shared in peer group X
- master:X
-
mount is slave to peer group X
- propagate_from:X
-
mount is slave and receives propagation from peer group X (*)
- unbindable
-
mount is unbindable
-
(*) X is the closest dominant peer group under the process's root.
If X is the immediate master of the mount,
or if there is no dominant peer group under the same root,
then only the "master:X" field is present
and not the "propagate_from:X" field.
For more information on mount propagation see:
Documentation/filesystems/sharedsubtree.txt
in the Linux kernel source tree.
- /proc/[pid]/mounts (since Linux 2.4.19)
-
This is a list of all the filesystems currently mounted in the
process's mount namespace.
The format of this file is documented in
fstab(5).
Since kernel version 2.6.15, this file is pollable:
after opening the file for reading, a change in this file
(i.e., a filesystem mount or unmount) causes
select(2)
to mark the file descriptor as readable, and
poll(2)
and
epoll_wait(2)
mark the file as having an error condition.
- /proc/[pid]/mountstats (since Linux 2.6.17)
-
This file exports information (statistics, configuration information)
about the mount points in the process's name space.
Lines in this file have the form:
device /dev/sda7 mounted on /home with fstype ext3 [statistics]
( 1 ) ( 2 ) (3 ) (4)
-
The fields in each line are:
-
- (1)
-
The name of the mounted device
(or "nodevice" if there is no corresponding device).
- (2)
-
The mount point within the filesystem tree.
- (3)
-
The filesystem type.
- (4)
-
Optional statistics and configuration information.
Currently (as at Linux 2.6.26), only NFS filesystems export
information via this field.
-
This file is readable only by the owner of the process.
- /proc/[pid]/ns/ (since Linux 3.0)
-
This is a subdirectory containing one entry for each namespace that
supports being manipulated by
setns(2).
For information about namespaces, see
clone(2).
- /proc/[pid]/ns/ipc (since Linux 3.0)
-
Bind mounting this file (see
mount(2))
to somewhere else in the filesystem keeps
the IPC namespace of the process specified by
pid
alive even if all processes currently in the namespace terminate.
Opening this file returns a file handle for the IPC namespace
of the process specified by
pid.
As long as this file descriptor remains open,
the IPC namespace will remain alive,
even if all processes in the namespace terminate.
The file descriptor can be passed to
setns(2).
- /proc/[pid]/ns/net (since Linux 3.0)
-
Bind mounting this file (see
mount(2))
to somewhere else in the filesystem keeps
the network namespace of the process specified by
pid
alive even if all processes in the namespace terminate.
Opening this file returns a file handle for the network namespace
of the process specified by
pid.
As long as this file descriptor remains open,
the network namespace will remain alive,
even if all processes in the namespace terminate.
The file descriptor can be passed to
setns(2).
- /proc/[pid]/ns/uts (since Linux 3.0)
-
Bind mounting this file (see
mount(2))
to somewhere else in the filesystem keeps
the UTS namespace of the process specified by
pid
alive even if all processes currently in the namespace terminate.
Opening this file returns a file handle for the UTS namespace
of the process specified by
pid.
As long as this file descriptor remains open,
the UTS namespace will remain alive,
even if all processes in the namespace terminate.
The file descriptor can be passed to
setns(2).
- /proc/[pid]/numa_maps (since Linux 2.6.14)
-
See
numa(7).
- /proc/[pid]/oom_adj (since Linux 2.6.11)
-
This file can be used to adjust the score used to select which process
should be killed in an out-of-memory (OOM) situation.
The kernel uses this value for a bit-shift operation of the process's
oom_score
value:
valid values are in the range -16 to +15,
plus the special value -17,
which disables OOM-killing altogether for this process.
A positive score increases the likelihood of this
process being killed by the OOM-killer;
a negative score decreases the likelihood.
-
The default value for this file is 0;
a new process inherits its parent's
oom_adj
setting.
A process must be privileged
(CAP_SYS_RESOURCE)
to update this file.
-
Since Linux 2.6.36, use of this file is deprecated in favor of
/proc/[pid]/oom_score_adj.
- /proc/[pid]/oom_score (since Linux 2.6.11)
-
This file displays the current score that the kernel gives to
this process for the purpose of selecting a process
for the OOM-killer.
A higher score means that the process is more likely to be
selected by the OOM-killer.
The basis for this score is the amount of memory used by the process,
with increases (+) or decreases (-) for factors including:
-
- *
-
whether the process creates a lot of children using
fork(2)
(+);
- *
-
whether the process has been running a long time,
or has used a lot of CPU time (-);
- *
-
whether the process has a low nice value (i.e., > 0) (+);
- *
-
whether the process is privileged (-); and
- *
-
whether the process is making direct hardware access (-).
-
The
oom_score
also reflects the adjustment specified by the
oom_score_adj
or
oom_adj
setting for the process.
- /proc/[pid]/oom_score_adj (since Linux 2.6.36)
-
This file can be used to adjust the badness heuristic used to select which
process gets killed in out-of-memory conditions.
The badness heuristic assigns a value to each candidate task ranging from 0
(never kill) to 1000 (always kill) to determine which process is targeted.
The units are roughly a proportion along that range of
allowed memory the process may allocate from,
based on an estimation of its current memory and swap use.
For example, if a task is using all allowed memory,
its badness score will be 1000.
If it is using half of its allowed memory, its score will be 500.
There is an additional factor included in the badness score: root
processes are given 3% extra memory over other tasks.
The amount of "allowed" memory depends on the context
in which the OOM-killer was called.
If it is due to the memory assigned to the allocating task's cpuset
being exhausted,
the allowed memory represents the set of mems assigned to that
cpuset (see
cpuset(7)).
If it is due to a mempolicy's node(s) being exhausted,
the allowed memory represents the set of mempolicy nodes.
If it is due to a memory limit (or swap limit) being reached,
the allowed memory is that configured limit.
Finally, if it is due to the entire system being out of memory, the
allowed memory represents all allocatable resources.
The value of
oom_score_adj
is added to the badness score before it
is used to determine which task to kill.
Acceptable values range from -1000
(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).
This allows user space to control the preference for OOM-killing,
ranging from always preferring a certain
task or completely disabling it from OOM-killing.
The lowest possible value, -1000, is
equivalent to disabling OOM-killing entirely for that task,
since it will always report a badness score of 0.
Consequently, it is very simple for user space to define
the amount of memory to consider for each task.
Setting a
oom_score_adj
value of +500, for example,
is roughly equivalent to allowing the remainder of tasks sharing the
same system, cpuset, mempolicy, or memory controller resources
to use at least 50% more memory.
A value of -500, on the other hand, would be roughly
equivalent to discounting 50% of the task's
allowed memory from being considered as scoring against the task.
For backward compatibility with previous kernels,
/proc/[pid]/oom_adj
can still be used to tune the badness score.
Its value is
scaled linearly with
oom_score_adj.
Writing to
/proc/[pid]/oom_score_adj
or
/proc/[pid]/oom_adj
will change the other with its scaled value.
- /proc/[pid]/pagemap (since Linux 2.6.25)
-
This file shows the mapping of each of the process's virtual pages
into physical page frames or swap area.
It contains one 64-bit value for each virtual page,
with the bits set as follows:
-
- 63
-
If set, the page is present in RAM.
- 62
-
If set, the page is in swap space
- 61 (since Linux 3.5)
-
The page is a file-mapped page or a shared anonymous page.
- 60-56 (since Linux 3.11)
-
Zero
- 55 (Since Linux 3.11)
-
PTE is soft-dirty
(see the kernel source file
Documentation/vm/soft-dirty.txt).
- 54-0
-
If the page is present in RAM (bit 63), then these bits
provide the page frame number, which can be used to index
/proc/kpageflags
and
/proc/kpagecount.
If the page is present in swap (bit 62),
then bits 4-0 give the swap type, and bits 54-5 encode the swap offset.
-
Before Linux 3.11, bits 60-55 were
used to encode the base-2 log of the page size.
-
To employ
/proc/[pid]/pagemap
efficiently, use
/proc/[pid]/maps
to determine which areas of memory are actually mapped and seek
to skip over unmapped regions.
-
The
/proc/[pid]/pagemap
file is present only if the
CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
- /proc/[pid]/personality (since Linux 2.6.28)
-
This read-only file exposes the process's execution domain, as set by
personality(2).
The value is displayed in hexadecimal notation.
- /proc/[pid]/root
-
UNIX and Linux support the idea of a per-process root of the
filesystem, set by the
chroot(2)
system call.
This file is a symbolic link that points to the process's
root directory, and behaves in the same way as
exe,
and
fd/*.
In a multithreaded process, the contents of this symbolic link
are not available if the main thread has already terminated
(typically by calling
pthread_exit(3)).
- /proc/[pid]/smaps (since Linux 2.6.14)
-
This file shows memory consumption for each of the process's mappings.
For each mapping there is a series of lines such as the following:
00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash
Size: 552 kB
Rss: 460 kB
Pss: 100 kB
Shared_Clean: 452 kB
Shared_Dirty: 0 kB
Private_Clean: 8 kB
Private_Dirty: 0 kB
Referenced: 460 kB
Anonymous: 0 kB
AnonHugePages: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
The first of these lines shows the same information as is displayed
for the mapping in
/proc/[pid]/maps.
The remaining lines show the size of the mapping,
the amount of the mapping that is currently resident in RAM ("Rss"),
the process' proportional share of this mapping ("Pss"),
the number of clean and dirty shared pages in the mapping,
and the number of clean and dirty private pages in the mapping.
"Referenced" indicates the amount of memory currently marked as
referenced or accessed.
"Anonymous" shows the amount of memory
that does not belong to any file.
"Swap" shows how much
would-be-anonymous memory is also used, but out on swap.
The "KernelPageSize" entry is the page size used by the kernel to back a VMA.
This matches the size used by the MMU in the majority of cases.
However, one counter-example occurs on PPC64 kernels
whereby a kernel using 64K as a base page size may still use 4K
pages for the MMU on older processors.
To distinguish, this
patch reports "MMUPageSize" as the page size used by the MMU.
The "Locked" indicates whether the mapping is locked in memory
or not.
"VmFlags" field represents the kernel flags associated with
the particular virtual memory area in two letter encoded manner.
The codes are the following:
rd - readable
wr - writable
ex - executable
sh - shared
mr - may read
mw - may write
me - may execute
ms - may share
gd - stack segment grows down
pf - pure PFN range
dw - disabled write to the mapped file
lo - pages are locked in memory
io - memory mapped I/O area
sr - sequential read advise provided
rr - random read advise provided
dc - do not copy area on fork
de - do not expand area on remapping
ac - area is accountable
nr - swap space is not reserved for the area
ht - area uses huge tlb pages
nl - non-linear mapping
ar - architecture specific flag
dd - do not include area into core dump
sd - soft-dirty flag
mm - mixed map area
hg - huge page advise flag
nh - no-huge page advise flag
mg - mergeable advise flag
The
/proc/[pid]/smaps
file is present only if the
CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
- /proc/[pid]/stack (since Linux 2.6.29)
-
This file provides a symbolic trace of the function calls in this
process's kernel stack.
This file is provided only if the kernel was built with the
CONFIG_STACKTRACE
configuration option.
- /proc/[pid]/stat
-
Status information about the process.
This is used by
ps(1).
It is defined in the kernel source file
fs/proc/array.c.
The fields, in order, with their proper
scanf(3)
format specifiers, are:
-
- (1) pid %d
-
The process ID.
- (2) comm %s
-
The filename of the executable, in parentheses.
This is visible whether or not the executable is swapped out.
- (3) state %c
-
One of the following characters, indicating process state:
-
- R
-
Running
- S
-
Sleeping in an interruptible wait
- D
-
Waiting in uninterruptible
disk sleep
- Z
-
Zombie
- T
-
Stopped (on a signal) or (before Linux 2.6.33) trace stopped
- t
-
Tracing stop (Linux 2.6.33 onward)
- W
-
Paging (only before Linux 2.6.0)
- X
-
Dead (from Linux 2.6.0 onward)
- x
-
Dead (Linux 2.6.33 to
3.13 only)
- K
-
Wakekill (Linux 2.6.33 to
3.13 only)
- W
-
Waking (Linux 2.6.33 to
3.13 only)
- P
-
Parked (Linux 3.9 to
3.13 only)
- (4) ppid %d
-
The PID of the parent of this process.
- (5) pgrp %d
-
The process group ID of the process.
- (6) session %d
-
The session ID of the process.
- (7) tty_nr %d
-
The controlling terminal of the process.
(The minor device number is contained in the combination of bits
31 to 20 and 7 to 0;
the major device number is in bits 15 to 8.)
- (8) tpgid %d
-
The ID of the foreground process group of the controlling
terminal of the process.
- (9) flags %u
-
The kernel flags word of the process.
For bit meanings,
see the PF_* defines in the Linux kernel source file
include/linux/sched.h.
Details depend on the kernel version.
The format for this field was %lu before Linux 2.6.
- (1) minflt %lu
-
The number of minor faults the process has made which have not
required loading a memory page from disk.
- (11) cminflt %lu
-
The number of minor faults that the process's
waited-for children have made.
- (12) majflt %lu
-
The number of major faults the process has made which have
required loading a memory page from disk.
- (13) cmajflt %lu
-
The number of major faults that the process's
waited-for children have made.
- (14) utime %lu
-
Amount of time that this process has been scheduled in user mode,
measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
This includes guest time, guest_time
(time spent running a virtual CPU, see below),
so that applications that are not aware of the guest time field
do not lose that time from their calculations.
- (15) stime %lu
-
Amount of time that this process has been scheduled in kernel mode,
measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
- (16) cutime %ld
-
Amount of time that this process's
waited-for children have been scheduled in user mode,
measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
(See also
times(2).)
This includes guest time, cguest_time
(time spent running a virtual CPU, see below).
- (17) cstime %ld
-
Amount of time that this process's
waited-for children have been scheduled in kernel mode,
measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
- (18) priority %ld
-
(Explanation for Linux 2.6)
For processes running a real-time scheduling policy
(policy
below; see
sched_setscheduler(2)),
this is the negated scheduling priority, minus one;
that is, a number in the range -2 to -100,
corresponding to real-time priorities 1 to 99.
For processes running under a non-real-time scheduling policy,
this is the raw nice value
(setpriority(2))
as represented in the kernel.
The kernel stores nice values as numbers
in the range 0 (high) to 39 (low),
corresponding to the user-visible nice range of -20 to 19.
Before Linux 2.6, this was a scaled value based on
the scheduler weighting given to this process.
- (19) nice %ld
-
The nice value (see
setpriority(2)),
a value in the range 19 (low priority) to -20 (high priority).
- (20) num_threads %ld
-
Number of threads in this process (since Linux 2.6).
Before kernel 2.6, this field was hard coded to 0 as a placeholder
for an earlier removed field.
- (21) itrealvalue %ld
-
The time in jiffies before the next
SIGALRM
is sent to the process due to an interval timer.
Since kernel 2.6.17, this field is no longer maintained,
and is hard coded as 0.
- (22) starttime %llu
-
The time the process started after system boot.
In kernels before Linux 2.6, this value was expressed in jiffies.
Since Linux 2.6, the value is expressed in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
The format for this field was %lu before Linux 2.6.
- (23) vsize %lu
-
Virtual memory size in bytes.
- (24) rss %ld
-
Resident Set Size: number of pages the process has in real memory.
This is just the pages which
count toward text, data, or stack space.
This does not include pages
which have not been demand-loaded in, or which are swapped out.
- (25) rsslim %lu
-
Current soft limit in bytes on the rss of the process;
see the description of
RLIMIT_RSS
in
getrlimit(2).
- (26) startcode %lu
-
The address above which program text can run.
- (27) endcode %lu
-
The address below which program text can run.
- (28) startstack %lu
-
The address of the start (i.e., bottom) of the stack.
- (29) kstkesp %lu
-
The current value of ESP (stack pointer), as found in the
kernel stack page for the process.
- (30) kstkeip %lu
-
The current EIP (instruction pointer).
- (31) signal %lu
-
The bitmap of pending signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/status
instead.
- (32) blocked %lu
-
The bitmap of blocked signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/status
instead.
- (33) sigignore %lu
-
The bitmap of ignored signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/status
instead.
- (34) sigcatch %lu
-
The bitmap of caught signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/status
instead.
- (35) wchan %lu
-
This is the "channel" in which the process is waiting.
It is the address of a location in the kernel where the process is sleeping.
The corresponding symbolic name can be found in
/proc/[pid]/wchan.
- (36) nswap %lu
-
Number of pages swapped (not maintained).
- (37) cnswap %lu
-
Cumulative nswap for child processes (not maintained).
- (38) exit_signal %d (since Linux 2.1.22)
-
Signal to be sent to parent when we die.
- (39) processor %d (since Linux 2.2.8)
-
CPU number last executed on.
- (40) rt_priority %u (since Linux 2.5.19)
-
Real-time scheduling priority, a number in the range 1 to 99 for
processes scheduled under a real-time policy,
or 0, for non-real-time processes (see
sched_setscheduler(2)).
- (41) policy %u (since Linux 2.5.19)
-
Scheduling policy (see
sched_setscheduler(2)).
Decode using the SCHED_* constants in
linux/sched.h.
The format for this field was %lu before Linux 2.6.22.
- (42) delayacct_blkio_ticks %llu (since Linux 2.6.18)
-
Aggregated block I/O delays, measured in clock ticks (centiseconds).
- (43) guest_time %lu (since Linux 2.6.24)
-
Guest time of the process (time spent running a virtual CPU
for a guest operating system), measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
- (44) cguest_time %ld (since Linux 2.6.24)
-
Guest time of the process's children, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
- (45) start_data %lu (since Linux 3.3)
-
Address above which program initialized and
uninitialized (BSS) data are placed.
- (46) end_data %lu (since Linux 3.3)
-
Address below which program initialized and
uninitialized (BSS) data are placed.
- (47) start_brk %lu (since Linux 3.3)
-
Address above which program heap can be expanded with
brk(2).
- (48) arg_start %lu (since Linux 3.5)
-
Address above which program command-line arguments
(argv)
are placed.
- (49) arg_end %lu (since Linux 3.5)
-
Address below program command-line arguments
(argv)
are placed.
- (50) env_start %lu (since Linux 3.5)
-
Address above which program environment is placed.
- (51) env_end %lu (since Linux 3.5)
-
Address below which program environment is placed.
- (52) exit_code %d (since Linux 3.5)
-
The thread's exit status in the form reported by
waitpid(2).
- /proc/[pid]/statm
-
Provides information about memory usage, measured in pages.
The columns are:
size (1) total program size
(same as VmSize in /proc/[pid]/status)
resident (2) resident set size
(same as VmRSS in /proc/[pid]/status)
share (3) shared pages (i.e., backed by a file)
text (4) text (code)
lib (5) library (unused in Linux 2.6)
data (6) data + stack
dt (7) dirty pages (unused in Linux 2.6)
- /proc/[pid]/status
-
Provides much of the information in
/proc/[pid]/stat
and
/proc/[pid]/statm
in a format that's easier for humans to parse.
Here's an example:
$ cat /proc/$$/status
Name: bash
State: S (sleeping)
Tgid: 3515
Pid: 3515
PPid: 3452
TracerPid: 0
Uid: 1000 1000 1000 1000
Gid: 100 100 100 100
FDSize: 256
Groups: 16 33 100
VmPeak: 9136 kB
VmSize: 7896 kB
VmLck: 0 kB
VmHWM: 7572 kB
VmRSS: 6316 kB
VmData: 5224 kB
VmStk: 88 kB
VmExe: 572 kB
VmLib: 1708 kB
VmPTE: 20 kB
Threads: 1
SigQ: 0/3067
SigPnd:<PHONE_NUMBER>000000
ShdPnd:<PHONE_NUMBER>000000
SigBlk:<PHONE_NUMBER>010000
SigIgn:<PHONE_NUMBER>384004
SigCgt: 000000004b813efb
CapInh:<PHONE_NUMBER>000000
CapPrm:<PHONE_NUMBER>000000
CapEff:<PHONE_NUMBER>000000
CapBnd: ffffffffffffffff
Cpus_allowed: 00000001
Cpus_allowed_list: 0
Mems_allowed: 1
Mems_allowed_list: 0
voluntary_ctxt_switches: 150
nonvoluntary_ctxt_switches: 545
-
The fields are as follows:
-
- *
-
Name:
Command run by this process.
- *
-
State:
Current state of the process.
One of
"R (running)",
"S (sleeping)",
"D (disk sleep)",
"T (stopped)",
"T (tracing stop)",
"Z (zombie)",
or
"X (dead)".
- *
-
Tgid:
Thread group ID (i.e., Process ID).
- *
-
Pid:
Thread ID (see
gettid(2)).
- *
-
PPid:
PID of parent process.
- *
-
TracerPid:
PID of process tracing this process (0 if not being traced).
- *
-
Uid, Gid:
Real, effective, saved set, and filesystem UIDs (GIDs).
- *
-
FDSize:
Number of file descriptor slots currently allocated.
- *
-
Groups:
Supplementary group list.
- *
-
VmPeak:
Peak virtual memory size.
- *
-
VmSize:
Virtual memory size.
- *
-
VmLck:
Locked memory size (see
mlock(3)).
- *
-
VmHWM:
Peak resident set size ("high water mark").
- *
-
VmRSS:
Resident set size.
- *
-
VmData, VmStk, VmExe:
Size of data, stack, and text segments.
- *
-
VmLib:
Shared library code size.
- *
-
VmPTE:
Page table entries size (since Linux 2.6.10).
- *
-
Threads:
Number of threads in process containing this thread.
- *
-
SigQ:
This field contains two slash-separated numbers that relate to
queued signals for the real user ID of this process.
The first of these is the number of currently queued
signals for this real user ID, and the second is the
resource limit on the number of queued signals for this process
(see the description of
RLIMIT_SIGPENDING
in
getrlimit(2)).
- *
-
SigPnd, ShdPnd:
Number of signals pending for thread and for process as a whole (see
pthreads(7)
and
signal(7)).
- *
-
SigBlk, SigIgn, SigCgt:
Masks indicating signals being blocked, ignored, and caught (see
signal(7)).
- *
-
CapInh, CapPrm, CapEff:
Masks of capabilities enabled in inheritable, permitted, and effective sets
(see
capabilities(7)).
- *
-
CapBnd:
Capability Bounding set
(since kernel 2.6.26, see
capabilities(7)).
- *
-
Cpus_allowed:
Mask of CPUs on which this process may run
(since Linux 2.6.24, see
cpuset(7)).
- *
-
Cpus_allowed_list:
Same as previous, but in "list format"
(since Linux 2.6.26, see
cpuset(7)).
- *
-
Mems_allowed:
Mask of memory nodes allowed to this process
(since Linux 2.6.24, see
cpuset(7)).
- *
-
Mems_allowed_list:
Same as previous, but in "list format"
(since Linux 2.6.26, see
cpuset(7)).
- *
-
voluntary_ctxt_switches, nonvoluntary_ctxt_switches:
Number of voluntary and involuntary context switches (since Linux 2.6.23).
- /proc/[pid]/syscall (since Linux 2.6.27)
-
This file exposes the system call number and argument registers for the
system call currently being executed by the process,
followed by the values of the stack pointer and program counter registers.
The values of all six argument registers are exposed,
although most system calls use fewer registers.
If the process is blocked, but not in a system call,
then the file displays -1 in place of the system call number,
followed by just the values of the stack pointer and program counter.
If process is not blocked, then file contains just the string "running".
This file is present only if the kernel was configured with
CONFIG_HAVE_ARCH_TRACEHOOK.
- /proc/[pid]/task (since Linux 2.6.0-test6)
-
This is a directory that contains one subdirectory
for each thread in the process.
The name of each subdirectory is the numerical thread ID
([tid])
of the thread (see
gettid(2)).
Within each of these subdirectories, there is a set of
files with the same names and contents as under the
/proc/[pid]
directories.
For attributes that are shared by all threads, the contents for
each of the files under the
task/[tid]
subdirectories will be the same as in the corresponding
file in the parent
/proc/[pid]
directory
(e.g., in a multithreaded process, all of the
task/[tid]/cwd
files will have the same value as the
/proc/[pid]/cwd
file in the parent directory, since all of the threads in a process
share a working directory).
For attributes that are distinct for each thread,
the corresponding files under
task/[tid]
may have different values (e.g., various fields in each of the
task/[tid]/status
files may be different for each thread).
In a multithreaded process, the contents of the
/proc/[pid]/task
directory are not available if the main thread has already terminated
(typically by calling
pthread_exit(3)).
- /proc/[pid]/wchan (since Linux 2.6.0)
-
The symbolic name corresponding to the location
in the kernel where the process is sleeping.
- /proc/apm
-
Advanced power management version and battery information when
CONFIG_APM
is defined at kernel compilation time.
- /proc/bus
-
Contains subdirectories for installed busses.
- /proc/bus/pccard
-
Subdirectory for PCMCIA devices when
CONFIG_PCMCIA
is set at kernel compilation time.
- /proc/[pid]/timers (since Linux 3.10)
-
A list of the POSIX timers for this process.
Each timer is listed with a line that started with the string "ID:".
For example:
ID: 1
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 0
ID: 0
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 1
The lines shown for each timer have the following meanings:
-
- ID
-
The ID for this timer.
This is not the same as the timer ID returned by
timer_create(2);
rather, it is the same kernel-internal ID that is available via the
si_timerid
field of the
siginfo_t
structure (see
sigaction(2)).
- signal
-
This is the signal number that this timer uses to deliver notifications
followed by a slash, and then the
sigev_value.sival_ptr
value supplied to the signal handler.
Valid only for timers that notify via a signal.
- notify
-
The part before the slash specifies the mechanism
that this timer uses to deliver notifications,
and is one of "thread", "signal", or "none".
Immediately following the slash is either the string "tid" for timers
with
SIGEV_THREAD_ID
notification, or "pid" for timers that notify by other mechanisms.
Following the "." is the PID of the process that will be delivered
a signal if the timer delivers notifications via a signal.
- ClockID
-
This field identifies the clock that the timer uses for measuring time.
For most clocks, this is a number that matches one of the user-space
CLOCK_*
constants exposed via
<time.h>.
CLOCK_PROCESS_CPUTIME_ID
timers display with a value of -6
in this field.
CLOCK_THREAD_CPUTIME_ID
timers display with a value of -2
in this field.
- /proc/bus/pccard/drivers
-
- /proc/bus/pci
-
Contains various bus subdirectories and pseudo-files containing
information about PCI busses, installed devices, and device
drivers.
Some of these files are not ASCII.
- /proc/bus/pci/devices
-
Information about PCI devices.
They may be accessed through
lspci(8)
and
setpci(8).
- /proc/cmdline
-
Arguments passed to the Linux kernel at boot time.
Often done via a boot manager such as
lilo(8)
or
grub(8).
- /proc/config.gz (since Linux 2.6)
-
This file exposes the configuration options that were used
to build the currently running kernel,
in the same format as they would be shown in the
.config
file that resulted when configuring the kernel (using
make xconfig,
make config,
or similar).
The file contents are compressed; view or search them using
zcat(1)
and
zgrep(1).
As long as no changes have been made to the following file,
the contents of
/proc/config.gz
are the same as those provided by :
cat /lib/modules/$(uname -r)/build/.config
-
/proc/config.gz
is provided only if the kernel is configured with
CONFIG_IKCONFIG_PROC.
- /proc/cpuinfo
-
This is a collection of CPU and system architecture dependent items,
for each supported architecture a different list.
Two common entries are processor which gives CPU number and
bogomips; a system constant that is calculated
during kernel initialization.
SMP machines have information for
each CPU.
The
lscpu(1)
command gathers its information from this file.
- /proc/devices
-
Text listing of major numbers and device groups.
This can be used by MAKEDEV scripts for consistency with the kernel.
- /proc/diskstats (since Linux 2.5.69)
-
This file contains disk I/O statistics for each disk device.
See the Linux kernel source file
Documentation/iostats.txt
for further information.
- /proc/dma
-
This is a list of the registered ISA DMA (direct memory access)
channels in use.
- /proc/driver
-
Empty subdirectory.
- /proc/execdomains
-
List of the execution domains (ABI personalities).
- /proc/fb
-
Frame buffer information when
CONFIG_FB
is defined during kernel compilation.
- /proc/filesystems
-
A text listing of the filesystems which are supported by the kernel,
namely filesystems which were compiled into the kernel or whose kernel
modules are currently loaded.
(See also
filesystems(5).)
If a filesystem is marked with "nodev",
this means that it does not require a block device to be mounted
(e.g., virtual filesystem, network filesystem).
Incidentally, this file may be used by
mount(8)
when no filesystem is specified and it didn't manage to determine the
filesystem type.
Then filesystems contained in this file are tried
(excepted those that are marked with "nodev").
- /proc/fs
-
Contains subdirectories that in turn contain files
with information about (certain) mounted filesystems.
- /proc/ide
-
This directory
exists on systems with the IDE bus.
There are directories for each IDE channel and attached device.
Files include:
cache buffer size in KB
capacity number of sectors
driver driver version
geometry physical and logical geometry
identify in hexadecimal
media media type
model manufacturer's model number
settings drive settings
smart_thresholds in hexadecimal
smart_values in hexadecimal
The
hdparm(8)
utility provides access to this information in a friendly format.
- /proc/interrupts
-
This is used to record the number of interrupts per CPU per IO device.
Since Linux 2.6.24,
for the i386 and x86_64 architectures, at least, this also includes
interrupts internal to the system (that is, not associated with a device
as such), such as NMI (nonmaskable interrupt), LOC (local timer interrupt),
and for SMP systems, TLB (TLB flush interrupt), RES (rescheduling
interrupt), CAL (remote function call interrupt), and possibly others.
Very easy to read formatting, done in ASCII.
- /proc/iomem
-
I/O memory map in Linux 2.4.
- /proc/ioports
-
This is a list of currently registered Input-Output port regions that
are in use.
- /proc/kallsyms (since Linux 2.5.71)
-
This holds the kernel exported symbol definitions used by the
modules(X)
tools to dynamically link and bind loadable modules.
In Linux 2.5.47 and earlier, a similar file with slightly different syntax
was named
ksyms.
- /proc/kcore
-
This file represents the physical memory of the system and is stored
in the ELF core file format.
With this pseudo-file, and an unstripped
kernel
(/usr/src/linux/vmlinux)
binary, GDB can be used to
examine the current state of any kernel data structures.
The total length of the file is the size of physical memory (RAM) plus
4KB.
- /proc/kmsg
-
This file can be used instead of the
syslog(2)
system call to read kernel messages.
A process must have superuser
privileges to read this file, and only one process should read this
file.
This file should not be read if a syslog process is running
which uses the
syslog(2)
system call facility to log kernel messages.
Information in this file is retrieved with the
dmesg(1)
program.
- /proc/kpagecount (since Linux 2.6.25)
-
This file contains a 64-bit count of the number of
times each physical page frame is mapped,
indexed by page frame number (see the discussion of
/proc/[pid]/pagemap).
-
The
/proc/kpagecount
file is present only if the
CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
- /proc/kpageflags (since Linux 2.6.25)
-
This file contains 64-bit masks corresponding to each physical page frame;
it is indexed by page frame number (see the discussion of
/proc/[pid]/pagemap).
The bits are as follows:
0 - KPF_LOCKED
1 - KPF_ERROR
2 - KPF_REFERENCED
3 - KPF_UPTODATE
4 - KPF_DIRTY
5 - KPF_LRU
6 - KPF_ACTIVE
7 - KPF_SLAB
8 - KPF_WRITEBACK
9 - KPF_RECLAIM
10 - KPF_BUDDY
11 - KPF_MMAP (since Linux 2.6.31)
12 - KPF_ANON (since Linux 2.6.31)
13 - KPF_SWAPCACHE (since Linux 2.6.31)
14 - KPF_SWAPBACKED (since Linux 2.6.31)
15 - KPF_COMPOUND_HEAD (since Linux 2.6.31)
16 - KPF_COMPOUND_TAIL (since Linux 2.6.31)
16 - KPF_HUGE (since Linux 2.6.31)
18 - KPF_UNEVICTABLE (since Linux 2.6.31)
19 - KPF_HWPOISON (since Linux 2.6.31)
20 - KPF_NOPAGE (since Linux 2.6.31)
21 - KPF_KSM (since Linux 2.6.32)
22 - KPF_THP (since Linux 3.4)
For further details on the meanings of these bits,
see the kernel source file
Documentation/vm/pagemap.txt.
Before kernel 2.6.29,
KPF_WRITEBACK,
KPF_RECLAIM,
KPF_BUDDY,
and
KPF_LOCKED
did not report correctly.
-
The
/proc/kpageflags
file is present only if the
CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
- /proc/ksyms (Linux 1.1.23-2.5.47)
-
See
/proc/kallsyms.
- /proc/loadavg
-
The first three fields in this file are load average figures
giving the number of jobs in the run queue (state R)
or waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes.
They are the same as the load average numbers given by
uptime(1)
and other programs.
The fourth field consists of two numbers separated by a slash (/).
The first of these is the number of currently runnable kernel
scheduling entities (processes, threads).
The value after the slash is the number of kernel scheduling entities
that currently exist on the system.
The fifth field is the PID of the process that was most
recently created on the system.
- /proc/locks
-
This file shows current file locks
(flock(2) and fcntl(2))
and leases
(fcntl(2)).
- /proc/malloc (only up to and including Linux 2.2)
-
This file is present only if
CONFIG_DEBUG_MALLOC
was defined during compilation.
- /proc/meminfo
-
This file reports statistics about memory usage on the system.
It is used by
free(1)
to report the amount of free and used memory (both physical and swap)
on the system as well as the shared memory and buffers used by the
kernel.
Each line of the file consists of a parameter name, followed by a colon,
the value of the parameter, and an option unit of measurement (e.g., "kB").
The list below describes the parameter names and
the format specifier required to read the field value.
Except as noted below,
all of the fields have been present since at least Linux 2.6.0.
Some fields are displayed only if the kernel was configured
with various options; those dependencies are noted in the list.
-
- MemTotal %lu
-
Total usable RAM (i.e., physical RAM minus a few reserved
bits and the kernel binary code).
- MemFree %lu
-
The sum of
LowFree+HighFree.
- Buffers %lu
-
Relatively temporary storage for raw disk blocks that
shouldn't get tremendously large (20MB or so).
- Cached %lu
-
In-memory cache for files read from the disk (the page cache).
Doesn't include
SwapCached.
- SwapCached %lu
-
Memory that once was swapped out, is swapped back in but
still also is in the swap file.
(If memory pressure is high, these pages
don't need to be swapped out again because they are already
in the swap file.
This saves I/O.)
- Active %lu
-
Memory that has been used more recently and usually not
reclaimed unless absolutely necessary.
- Inactive %lu
-
Memory which has been less recently used.
It is more eligible to be reclaimed for other purposes.
- Active(anon) %lu (since Linux 2.6.28)
-
[To be documented.]
- Inactive(anon) %lu (since Linux 2.6.28)
-
[To be documented.]
- Active(file) %lu (since Linux 2.6.28)
-
[To be documented.]
- Inactive(file) %lu (since Linux 2.6.28)
-
[To be documented.]
- Unevictable %lu (since Linux 2.6.28)
-
(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRU was required.)
[To be documented.]
- Mlocked %lu (since Linux 2.6.28)
-
(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRU was required.)
[To be documented.]
- HighTotal %lu
-
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
Total amount of highmem.
Highmem is all memory above ~860MB of physical memory.
Highmem areas are for use by user-space programs,
or for the page cache.
The kernel must use tricks to access
this memory, making it slower to access than lowmem.
- HighFree %lu
-
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
Amount of free highmem.
- LowTotal %lu
-
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
Total amount of lowmem.
Lowmem is memory which can be used for everything that
highmem can be used for, but it is also available for the
kernel's use for its own data structures.
Among many other things,
it is where everything from
Slab
is allocated.
Bad things happen when you're out of lowmem.
- LowFree %lu
-
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
Amount of free lowmem.
- MmapCopy %lu (since Linux 2.6.29)
-
(CONFIG_MMU
is required.)
[To be documented.]
- SwapTotal %lu
-
Total amount of swap space available.
- SwapFree %lu
-
Amount of swap space that is currently unused.
- Dirty %lu
-
Memory which is waiting to get written back to the disk.
- Writeback %lu
-
Memory which is actively being written back to the disk.
- AnonPages %lu (since Linux 2.6.18)
-
Non-file backed pages mapped into user-space page tables.
- Mapped %lu
-
Files which have been mapped into memory (with
mmap(2)),
such as libraries.
- Shmem %lu (since Linux 2.6.32)
-
[To be documented.]
- Slab %lu
-
In-kernel data structures cache.
- SReclaimable %lu (since Linux 2.6.19)
-
Part of
Slab,
that might be reclaimed, such as caches.
- SUnreclaim %lu (since Linux 2.6.19)
-
Part of
Slab,
that cannot be reclaimed on memory pressure.
- KernelStack %lu (since Linux 2.6.32)
-
Amount of memory allocated to kernel stacks.
- PageTables %lu (since Linux 2.6.18)
-
Amount of memory dedicated to the lowest level of page tables.
- Quicklists %lu (since Linux 2.6.27)
-
(CONFIG_QUICKLIST is required.)
[To be documented.]
- NFS_Unstable %lu (since Linux 2.6.18)
-
NFS pages sent to the server, but not yet committed to stable storage.
- Bounce %lu (since Linux 2.6.18)
-
Memory used for block device "bounce buffers".
- WritebackTmp %lu (since Linux 2.6.26)
-
Memory used by FUSE for temporary writeback buffers.
- CommitLimit %lu (since Linux 2.6.10)
-
This is the total amount of memory currently available to
be allocated on the system, expressed in kilobytes.
This limit is adhered to
only if strict overcommit accounting is enabled (mode 2 in
/proc/sys/vm/overcommit_memory).
The limit is calculated according to the formula described under
/proc/sys/vm/overcommit_memory.
For further details, see the kernel source file
Documentation/vm/overcommit-accounting.
- Committed_AS %lu
-
The amount of memory presently allocated on the system.
The committed memory is a sum of all of the memory which
has been allocated by processes, even if it has not been
"used" by them as of yet.
A process which allocates 1GB of memory (using
malloc(3)
or similar), but touches only 300MB of that memory will show up
as using only 300MB of memory even if it has the address space
allocated for the entire 1GB.
This 1GB is memory which has been "committed" to by the VM
and can be used at any time by the allocating application.
With strict overcommit enabled on the system (mode 2 in
IR /proc/sys/vm/overcommit_memory ),
allocations which would exceed the
CommitLimit
will not be permitted.
This is useful if one needs to guarantee that processes will not
fail due to lack of memory once that memory has been successfully allocated.
- VmallocTotal %lu
-
Total size of vmalloc memory area.
- VmallocUsed %lu
-
Amount of vmalloc area which is used.
- VmallocChunk %lu
-
Largest contiguous block of vmalloc area which is free.
- HardwareCorrupted %lu (since Linux 2.6.32)
-
(CONFIG_MEMORY_FAILURE is required.)
[To be documented.]
- AnonHugePages %lu (since Linux 2.6.38)
-
(CONFIG_TRANSPARENT_HUGEPAGE is required.)
Non-file backed huge pages mapped into user-space page tables.
- HugePages_Total %lu
-
(CONFIG_HUGETLB_PAGE is required.)
The size of the pool of huge pages.
- HugePages_Free %lu
-
(CONFIG_HUGETLB_PAGE is required.)
The number of huge pages in the pool that are not yet allocated.
- HugePages_Rsvd %lu (since Linux 2.6.17)
-
(CONFIG_HUGETLB_PAGE is required.)
This is the number of huge pages for
which a commitment to allocate from the pool has been made,
but no allocation has yet been made.
These reserved huge pages
guarantee that an application will be able to allocate a
huge page from the pool of huge pages at fault time.
- HugePages_Surp %lu (since Linux 2.6.24)
-
(CONFIG_HUGETLB_PAGE is required.)
This is the number of huge pages in
the pool above the value in
/proc/sys/vm/nr_hugepages.
The maximum number of surplus huge pages is controlled by
/proc/sys/vm/nr_overcommit_hugepages.
- Hugepagesize %lu
-
(CONFIG_HUGETLB_PAGE is required.)
The size of huge pages.
- /proc/modules
-
A text list of the modules that have been loaded by the system.
See also
lsmod(8).
- /proc/mounts
-
Before kernel 2.4.19, this file was a list
of all the filesystems currently mounted on the system.
With the introduction of per-process mount namespaces in
Linux 2.4.19, this file became a link to
/proc/self/mounts,
which lists the mount points of the process's own mount namespace.
The format of this file is documented in
fstab(5).
- /proc/mtrr
-
Memory Type Range Registers.
See the Linux kernel source file
Documentation/mtrr.txt
for details.
- /proc/net
-
various net pseudo-files, all of which give the status of some part of
the networking layer.
These files contain ASCII structures and are,
therefore, readable with
cat(1).
However, the standard
netstat(8)
suite provides much cleaner access to these files.
- /proc/net/arp
-
This holds an ASCII readable dump of the kernel ARP table used for
address resolutions.
It will show both dynamically learned and preprogrammed ARP entries.
The format is:
IP address HW type Flags HW address Mask Device
<IP_ADDRESS> 0x1 0x2 00:50:BF:25:68:F3 * eth0
<IP_ADDRESS> 0x1 0xc 00:00:00:00:00:00 * eth0
Here "IP address" is the IPv4 address of the machine and the "HW type"
is the hardware type of the address from RFC 826.
The flags are the internal
flags of the ARP structure (as defined in
/usr/include/linux/if_arp.h)
and
the "HW address" is the data link layer mapping for that IP address if
it is known.
- /proc/net/dev
-
The dev pseudo-file contains network device status information.
This gives
the number of received and sent packets, the number of errors and
collisions
and other basic statistics.
These are used by the
ifconfig(8)
program to report device status.
The format is:
Inter-| Receive | Transmit
face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
lo: 2776770 11307 0 0 0 0 0 0 2776770 11307 0 0 0 0 0 0
eth0: 1215645 2751 0 0 0 0 0 0 1782404 4324 0 0 0 427 0 0
ppp0: 1622270 5552 1 0 0 0 0 0<PHONE_NUMBER> 0 0 0 0 0 0
tap0: 7714 81 0 0 0 0 0 0 7714 81 0 0 0 0 0 0
- /proc/net/dev_mcast
-
Defined in
/usr/src/linux/net/core/dev_mcast.c:
indx interface_name dmi_u dmi_g dmi_address
2 eth0 1 0 01005e000001
3 eth1 1 0 01005e000001
4 eth2 1 0 01005e000001
- /proc/net/igmp
-
Internet Group Management Protocol.
Defined in
/usr/src/linux/net/core/igmp.c.
- /proc/net/rarp
-
This file uses the same format as the
arp
file and contains the current reverse mapping database used to provide
rarp(8)
reverse address lookup services.
If RARP is not configured into the
kernel,
this file will not be present.
- /proc/net/raw
-
Holds a dump of the RAW socket table.
Much of the information is not of
use
apart from debugging.
The "sl" value is the kernel hash slot for the
socket,
the "local_address" is the local address and protocol number pair.
"St" is
the internal status of the socket.
The "tx_queue" and "rx_queue" are the
outgoing and incoming data queue in terms of kernel memory usage.
The "tr", "tm->when", and "rexmits" fields are not used by RAW.
The "uid"
field holds the effective UID of the creator of the socket.
- /proc/net/snmp
-
This file holds the ASCII data needed for the IP, ICMP, TCP, and UDP
management
information bases for an SNMP agent.
- /proc/net/tcp
-
Holds a dump of the TCP socket table.
Much of the information is not
of use apart from debugging.
The "sl" value is the kernel hash slot
for the socket, the "local_address" is the local address and port number pair.
The "rem_address" is the remote address and port number pair
(if connected).
"St" is the internal status of the socket.
The "tx_queue" and "rx_queue" are the
outgoing and incoming data queue in terms of kernel memory usage.
The "tr", "tm->when", and "rexmits" fields hold internal information of
the kernel socket state and are only useful for debugging.
The "uid"
field holds the effective UID of the creator of the socket.
- /proc/net/udp
-
Holds a dump of the UDP socket table.
Much of the information is not of
use apart from debugging.
The "sl" value is the kernel hash slot for the
socket, the "local_address" is the local address and port number pair.
The "rem_address" is the remote address and port number pair
(if connected). "St" is the internal status of the socket.
The "tx_queue" and "rx_queue" are the outgoing and incoming data queue
in terms of kernel memory usage.
The "tr", "tm->when", and "rexmits" fields
are not used by UDP.
The "uid"
field holds the effective UID of the creator of the socket.
The format is:
sl local_address rem_address st tx_queue rx_queue tr rexmits tm->when uid
1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0
- /proc/net/unix
-
Lists the UNIX domain sockets present within the system and their
status.
The format is:
Num RefCount Protocol Flags Type St Path
0: 00000002 00000000 00000000 0001 03
1: 00000001 00000000 00010000 0001 01 /dev/printer
Here "Num" is the kernel table slot number, "RefCount" is the number
of users of the socket, "Protocol" is currently always 0, "Flags"
represent the internal kernel flags holding the status of the
socket.
Currently, type is always "1" (UNIX domain datagram sockets are
not yet supported in the kernel).
"St" is the internal state of the
socket and Path is the bound path (if any) of the socket.
- /proc/partitions
-
Contains the major and minor numbers of each partition as well as the number
of 1024-byte blocks and the partition name.
- /proc/pci
-
This is a listing of all PCI devices found during kernel initialization
and their configuration.
This file has been deprecated in favor of a new
/proc
interface for PCI
(/proc/bus/pci).
It became optional in Linux 2.2 (available with
CONFIG_PCI_OLD_PROC
set at kernel compilation).
It became once more nonoptionally enabled in Linux 2.4.
Next, it was deprecated in Linux 2.6 (still available with
CONFIG_PCI_LEGACY_PROC
set), and finally removed altogether since Linux 2.6.17.
- /proc/profile (since Linux 2.4)
-
This file is present only if the kernel was booted with the
profile=1
command-line option.
It exposes kernel profiling information in a binary format for use by
readprofile(1).
Writing (e.g., an empty string) to this file resets the profiling counters;
on some architectures,
writing a binary integer "profiling multiplier" of size
sizeof(int)
sets the profiling interrupt frequency.
- /proc/scsi
-
A directory with the
scsi
mid-level pseudo-file and various SCSI low-level
driver directories,
which contain a file for each SCSI host in this system, all of
which give the status of some part of the SCSI IO subsystem.
These files contain ASCII structures and are, therefore, readable with
cat(1).
You can also write to some of the files to reconfigure the subsystem or
switch certain features on or off.
- /proc/scsi/scsi
-
This is a listing of all SCSI devices known to the kernel.
The listing is similar to the one seen during bootup.
scsi currently supports only the add-single-device command which
allows root to add a hotplugged device to the list of known devices.
The command
echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi
will cause
host scsi1 to scan on SCSI channel 0 for a device on ID 5 LUN 0.
If there
is already a device known on this address or the address is invalid, an
error will be returned.
- /proc/scsi/[drivername]
-
[drivername] can currently be NCR53c7xx, aha152x, aha1542, aha1740,
aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000, pas16, qlogic,
scsi_debug, seagate, t128, u15-24f, ultrastore, or wd7000.
These directories show up for all drivers that registered at least one
SCSI HBA.
Every directory contains one file per registered host.
Every host-file is named after the number the host was assigned during
initialization.
Reading these files will usually show driver and host configuration,
statistics, and so on.
Writing to these files allows different things on different hosts.
For example, with the latency and nolatency commands,
root can switch on and off command latency measurement code in the
eata_dma driver.
With the lockup and unlock commands,
root can control bus lockups simulated by the scsi_debug driver.
- /proc/self
-
This directory refers to the process accessing the
/proc
filesystem,
and is identical to the
/proc
directory named by the process ID of the same process.
- /proc/slabinfo
-
Information about kernel caches.
Since Linux 2.6.16 this file is present only if the
CONFIG_SLAB
kernel configuration option is enabled.
The columns in
/proc/slabinfo
are:
cache-name
num-active-objs
total-objs
object-size
num-active-slabs
total-slabs
num-pages-per-slab
See
slabinfo(5)
for details.
- /proc/stat
-
kernel/system statistics.
Varies with architecture.
Common
entries include:
-
- cpu 3357 0 4313 1362393
-
The amount of time, measured in units of
USER_HZ (1/100ths of a second on most architectures, use
sysconf(_SC_CLK_TCK)
to obtain the right value),
that the system spent in various states:
-
- user
-
(1) Time spent in user mode.
- nice
-
(2) Time spent in user mode with low priority (nice).
- system
-
(3) Time spent in system mode.
- idle
-
(4) Time spent in the idle task.
This value should be USER_HZ times the
second entry in the
/proc/uptime
pseudo-file.
- iowait (since Linux 2.5.41)
-
(5) Time waiting for I/O to complete.
- irq (since Linux 2.6.0-test4)
-
(6) Time servicing interrupts.
- softirq (since Linux 2.6.0-test4)
-
(7) Time servicing softirqs.
- steal (since Linux 2.6.11)
-
(8) Stolen time, which is the time spent in other operating systems when
running in a virtualized environment
- guest (since Linux 2.6.24)
-
(9) Time spent running a virtual CPU for guest
operating systems under the control of the Linux kernel.
- guest_nice (since Linux 2.6.33)
-
(10) Time spent running a niced guest (virtual CPU for guest
operating systems under the control of the Linux kernel).
- page 5741 1808
-
The number of pages the system paged in and the number that were paged
out (from disk).
- swap 1 0
-
The number of swap pages that have been brought in and out.
-
-
intr 1462898
This line shows counts of interrupts serviced since boot time,
for each of the possible system interrupts.
The first column is the total of all interrupts serviced
including unnumbered architecture specific interrupts;
each subsequent column is the total for that particular numbered interrupt.
Unnumbered interrupts are not shown, only summed into the total.
- disk_io: (2,0):(31,30,5764,1,2) (3,0):...
-
(major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
(Linux 2.4 only)
- ctxt 115315
-
The number of context switches that the system underwent.
- btime 769041601
-
boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
- processes 86031
-
Number of forks since boot.
- procs_running 6
-
Number of processes in runnable state.
(Linux 2.5.45 onward.)
- procs_blocked 2
-
Number of processes blocked waiting for I/O to complete.
(Linux 2.5.45 onward.)
- /proc/swaps
-
Swap areas in use.
See also
swapon(8).
- /proc/sys
-
This directory (present since 1.3.57) contains a number of files
and subdirectories corresponding to kernel variables.
These variables can be read and sometimes modified using
the /proc filesystem, and the (deprecated)
sysctl(2)
system call.
- /proc/sys/abi (since Linux 2.4.10)
-
This directory may contain files with application binary information.
See the Linux kernel source file
Documentation/sysctl/abi.txt
for more information.
- /proc/sys/debug
-
This directory may be empty.
- /proc/sys/dev
-
This directory contains device-specific information (e.g.,
dev/cdrom/info).
On
some systems, it may be empty.
- /proc/sys/fs
-
This directory contains the files and subdirectories for kernel variables
related to filesystems.
- /proc/sys/fs/binfmt_misc
-
Documentation for files in this directory can be found
in the Linux kernel sources in
Documentation/binfmt_misc.txt.
- /proc/sys/fs/dentry-state (since Linux 2.2)
-
This file contains information about the status of the
directory cache (dcache).
The file contains six numbers,
nr_dentry, nr_unused, age_limit (age in seconds),
want_pages
(pages requested by system) and two dummy values.
-
- *
-
nr_dentry
is the number of allocated dentries (dcache entries).
This field is unused in Linux 2.2.
- *
-
nr_unused
is the number of unused dentries.
- *
-
age_limit
is the age in seconds after which dcache entries
can be reclaimed when memory is short.
- *
-
want_pages
is nonzero when the kernel has called shrink_dcache_pages() and the
dcache isn't pruned yet.
- /proc/sys/fs/dir-notify-enable
-
This file can be used to disable or enable the
dnotify
interface described in
fcntl(2)
on a system-wide basis.
A value of 0 in this file disables the interface,
and a value of 1 enables it.
- /proc/sys/fs/dquot-max
-
This file shows the maximum number of cached disk quota entries.
On some (2.4) systems, it is not present.
If the number of free cached disk quota entries is very low and
you have some awesome number of simultaneous system users,
you might want to raise the limit.
- /proc/sys/fs/dquot-nr
-
This file shows the number of allocated disk quota
entries and the number of free disk quota entries.
- /proc/sys/fs/epoll (since Linux 2.6.28)
-
This directory contains the file
max_user_watches,
which can be used to limit the amount of kernel memory consumed by the
epoll
interface.
For further details, see
epoll(7).
- /proc/sys/fs/file-max
-
This file defines
a system-wide limit on the number of open files for all processes.
(See also
setrlimit(2),
which can be used by a process to set the per-process limit,
RLIMIT_NOFILE,
on the number of files it may open.)
If you get lots
of error messages in the kernel log about running out of file handles
(look for "VFS: file-max limit <number> reached"),
try increasing this value:
echo 100000 > /proc/sys/fs/file-max
The kernel constant
NR_OPEN
imposes an upper limit on the value that may be placed in
file-max.
Privileged processes
(CAP_SYS_ADMIN)
can override the
file-max
limit.
- /proc/sys/fs/file-nr
-
This (read-only) file contains three numbers:
the number of allocated file handles
(i.e., the number of files presently opened);
the number of free file handles;
and the maximum number of file handles (i.e., the same value as
/proc/sys/fs/file-max).
If the number of allocated file handles is close to the
maximum, you should consider increasing the maximum.
Before Linux 2.6,
the kernel allocated file handles dynamically,
but it didn't free them again.
Instead the free file handles were kept in a list for reallocation;
the "free file handles" value indicates the size of that list.
A large number of free file handles indicates that there was
a past peak in the usage of open file handles.
Since Linux 2.6, the kernel does deallocate freed file handles,
and the "free file handles" value is always zero.
- /proc/sys/fs/inode-max (only present until Linux 2.2)
-
This file contains the maximum number of in-memory inodes.
This value should be 3-4 times larger
than the value in
file-max,
since stdin, stdout
and network sockets also need an inode to handle them.
When you regularly run out of inodes, you need to increase this value.
Starting with Linux 2.4,
there is no longer a static limit on the number of inodes,
and this file is removed.
- /proc/sys/fs/inode-nr
-
This file contains the first two values from
inode-state.
- /proc/sys/fs/inode-state
-
This file
contains seven numbers:
nr_inodes,
nr_free_inodes,
preshrink,
and four dummy values (always zero).
nr_inodes
is the number of inodes the system has allocated.
nr_free_inodes
represents the number of free inodes.
preshrink
is nonzero when the
nr_inodes
>
inode-max
and the system needs to prune the inode list instead of allocating more;
since Linux 2.4, this field is a dummy value (always zero).
- /proc/sys/fs/inotify (since Linux 2.6.13)
-
This directory contains files
max_queued_events, max_user_instances, and max_user_watches,
that can be used to limit the amount of kernel memory consumed by the
inotify
interface.
For further details, see
inotify(7).
- /proc/sys/fs/lease-break-time
-
This file specifies the grace period that the kernel grants to a process
holding a file lease
(fcntl(2))
after it has sent a signal to that process notifying it
that another process is waiting to open the file.
If the lease holder does not remove or downgrade the lease within
this grace period, the kernel forcibly breaks the lease.
- /proc/sys/fs/leases-enable
-
This file can be used to enable or disable file leases
(fcntl(2))
on a system-wide basis.
If this file contains the value 0, leases are disabled.
A nonzero value enables leases.
- /proc/sys/fs/mqueue (since Linux 2.6.6)
-
This directory contains files
msg_max, msgsize_max, and queues_max,
controlling the resources used by POSIX message queues.
See
mq_overview(7)
for details.
- /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
-
These files
allow you to change the value of the fixed UID and GID.
The default is 65534.
Some filesystems support only 16-bit UIDs and GIDs, although in Linux
UIDs and GIDs are 32 bits.
When one of these filesystems is mounted
with writes enabled, any UID or GID that would exceed 65535 is translated
to the overflow value before being written to disk.
- /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
-
The value in this file defines an upper limit for raising the capacity
of a pipe using the
fcntl(2)
F_SETPIPE_SZ
operation.
This limit applies only to unprivileged processes.
The default value for this file is 1,048,576.
The value assigned to this file may be rounded upward,
to reflect the value actually employed for a convenient implementation.
To determine the rounded-up value,
display the contents of this file after assigning a value to it.
The minimum value that can be assigned to this file is the system page size.
- /proc/sys/fs/protected_hardlinks (since Linux 3.6)
-
When the value in this file is 0,
no restrictions are placed on the creation of hard links
(i.e., this is the historical behavior before Linux 3.6).
When the value in this file is 1,
a hard link can be created to a target file
only if one of the following conditions is true:
-
- *
-
The caller has the
CAP_FOWNER
capability.
- *
-
The filesystem UID of the process creating the link matches
the owner (UID) of the target file
(as described in
credentials(7),
a process's filesystem UID is normally the same as its effective UID).
- *
-
All of the following conditions are true:
-
- •
-
the target is a regular file;
- •
-
the target file does not have its set-user-ID permission bit enabled;
- •
-
the target file does not have both its set-group-ID and
group-executable permission bits enabled; and
- •
-
the caller has permission to read and write the target file
(either via the file's permissions mask or because it has
suitable capabilities).
-
The default value in this file is 0.
Setting the value to 1
prevents a longstanding class of security issues caused by
hard-link-based time-of-check, time-of-use races,
most commonly seen in world-writable directories such as
/tmp.
The common method of exploiting this flaw
is to cross privilege boundaries when following a given hard link
(i.e., a root process follows a hard link created by another user).
Additionally, on systems without separated partitions,
this stops unauthorized users from "pinning" vulnerable set-user-ID and
set-group-ID files against being upgraded by
the administrator, or linking to special files.
- /proc/sys/fs/protected_symlinks (since Linux 3.6)
-
When the value in this file is 0,
no restrictions are placed on following symbolic links
(i.e., this is the historical behavior before Linux 3.6).
When the value in this file is 1, symbolic links are followed only
in the following circumstances:
-
- *
-
the filesystem UID of the process following the link matches
the owner (UID) of the symbolic link
(as described in
credentials(7),
a process's filesystem UID is normally the same as its effective UID);
- *
-
the link is not in a sticky world-writable directory; or
- *
-
the symbolic link and its parent directory have the same owner (UID)
-
A system call that fails to follow a symbolic link
because of the above restrictions returns the error
EACCES
in
errno.
-
The default value in this file is 0.
Setting the value to 1 avoids a longstanding class of security issues
based on time-of-check, time-of-use races when accessing symbolic links.
- /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
-
The value in this file determines whether core dump files are
produced for set-user-ID or otherwise protected/tainted binaries.
Three different integer values can be specified:
-
- 0 (default)
-
This provides the traditional (pre-Linux 2.6.13) behavior.
A core dump will not be produced for a process which has
changed credentials (by calling
seteuid(2),
setgid(2),
or similar, or by executing a set-user-ID or set-group-ID program)
or whose binary does not have read permission enabled.
- 1 ("debug")
-
All processes dump core when possible.
The core dump is owned by the filesystem user ID of the dumping process
and no security is applied.
This is intended for system debugging situations only.
Ptrace is unchecked.
- 2 ("suidsafe")
-
Any binary which normally would not be dumped (see "0" above)
is dumped readable by root only.
This allows the user to remove the core dump file but not to read it.
For security reasons core dumps in this mode will not overwrite one
another or other files.
This mode is appropriate when administrators are
attempting to debug problems in a normal environment.
-
Additionally, since Linux 3.6,
/proc/sys/kernel/core_pattern
must either be an absolute pathname
or a pipe command, as detailed in
core(5).
Warnings will be written to the kernel log if
core_pattern
does not follow these rules, and no core dump will be produced.
- /proc/sys/fs/super-max
-
This file
controls the maximum number of superblocks, and
thus the maximum number of mounted filesystems the kernel
can have.
You need increase only
super-max
if you need to mount more filesystems than the current value in
super-max
allows you to.
- /proc/sys/fs/super-nr
-
This file
contains the number of filesystems currently mounted.
- /proc/sys/kernel
-
This directory contains files controlling a range of kernel parameters,
as described below.
- /proc/sys/kernel/acct
-
This file
contains three numbers:
highwater,
lowwater,
and
frequency.
If BSD-style process accounting is enabled, these values control
its behavior.
If free space on filesystem where the log lives goes below
lowwater
percent, accounting suspends.
If free space gets above
highwater
percent, accounting resumes.
frequency
determines
how often the kernel checks the amount of free space (value is in
seconds).
Default values are 4, 2 and 30.
That is, suspend accounting if 2% or less space is free; resume it
if 4% or more space is free; consider information about amount of free space
valid for 30 seconds.
- /proc/sys/kernel/cap_last_cap (since Linux 3.2)
-
See
capabilities(7).
- /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
-
This file holds the value of the kernel
capability bounding set
(expressed as a signed decimal number).
This set is ANDed against the capabilities permitted to a process
during
execve(2).
Starting with Linux 2.6.25,
the system-wide capability bounding set disappeared,
and was replaced by a per-thread bounding set; see
capabilities(7).
- /proc/sys/kernel/core_pattern
-
See
core(5).
- /proc/sys/kernel/core_uses_pid
-
See
core(5).
- /proc/sys/kernel/ctrl-alt-del
-
This file
controls the handling of Ctrl-Alt-Del from the keyboard.
When the value in this file is 0, Ctrl-Alt-Del is trapped and
sent to the
init(8)
program to handle a graceful restart.
When the value is greater than zero, Linux's reaction to a Vulcan
Nerve Pinch (tm) will be an immediate reboot, without even
syncing its dirty buffers.
Note: when a program (like dosemu) has the keyboard in "raw"
mode, the ctrl-alt-del is intercepted by the program before it
ever reaches the kernel tty layer, and it's up to the program
to decide what to do with it.
- /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
-
The value in this file determines who can see kernel syslog contents.
A value of 0 in this file imposes no restrictions.
If the value is 1, only privileged users can read the kernel syslog.
(See
syslog(2)
for more details.)
Since Linux 3.4,
only users with the
CAP_SYS_ADMIN
capability may change the value in this file.
- /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
-
can be used to set the NIS/YP domainname and the
hostname of your box in exactly the same way as the commands
domainname(1)
and
hostname(1),
that is:
# echo 'darkstar' > /proc/sys/kernel/hostname
# echo 'mydomain' > /proc/sys/kernel/domainname
has the same effect as
# hostname 'darkstar'
# domainname 'mydomain'
Note, however, that the classic darkstar.frop.org has the
hostname "darkstar" and DNS (Internet Domain Name Server)
domainname "frop.org", not to be confused with the NIS (Network
Information Service) or YP (Yellow Pages) domainname.
These two
domain names are in general different.
For a detailed discussion
see the
hostname(1)
man page.
- /proc/sys/kernel/hotplug
-
This file
contains the path for the hotplug policy agent.
The default value in this file is
/sbin/hotplug.
- /proc/sys/kernel/htab-reclaim
-
(PowerPC only) If this file is set to a nonzero value,
the PowerPC htab
(see kernel file
Documentation/powerpc/ppc_htab.txt)
is pruned
each time the system hits the idle loop.
- /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
-
The value in this file determines whether kernel addresses are exposed via
/proc
files and other interfaces.
A value of 0 in this file imposes no restrictions.
If the value is 1, kernel pointers printed using the
%pK
format specifier will be replaced with zeros unless the user has the
CAP_SYSLOG
capability.
If the value is 2, kernel pointers printed using the
%pK
format specifier will be replaced with zeros regardless
of the user's capabilities.
The initial default value for this file was 1,
but the default was changed
to 0 in Linux 2.6.39.
Since Linux 3.4,
only users with the
CAP_SYS_ADMIN
capability can change the value in this file.
- /proc/sys/kernel/l2cr
-
(PowerPC only) This file
contains a flag that controls the L2 cache of G3 processor
boards.
If 0, the cache is disabled.
Enabled if nonzero.
- /proc/sys/kernel/modprobe
-
This file contains the path for the kernel module loader.
The default value is
/sbin/modprobe.
The file is present only if the kernel is built with the
CONFIG_MODULES
(CONFIG_KMOD
in Linux 2.6.26 and earlier)
option enabled.
It is described by the Linux kernel source file
Documentation/kmod.txt
(present only in kernel 2.4 and earlier).
- /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
-
A toggle value indicating if modules are allowed to be loaded
in an otherwise modular kernel.
This toggle defaults to off (0), but can be set true (1).
Once true, modules can be neither loaded nor unloaded,
and the toggle cannot be set back to false.
The file is present only if the kernel is built with the
CONFIG_MODULES
option enabled.
- /proc/sys/kernel/msgmax (since Linux 2.2)
-
This file defines
a system-wide limit specifying the maximum number of bytes in
a single message written on a System V message queue.
- /proc/sys/kernel/msgmni (since Linux 2.4)
-
This file defines the system-wide limit on the number of
message queue identifiers.
- /proc/sys/kernel/msgmnb (since Linux 2.2)
-
This file defines a system-wide parameter used to initialize the
msg_qbytes
setting for subsequently created message queues.
The
msg_qbytes
setting specifies the maximum number of bytes that may be written to the
message queue.
- /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
-
This is a read-only file that displays the upper limit on the
number of a process's group memberships.
- /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
-
These files
give substrings of
/proc/version.
- /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
-
These files duplicate the files
/proc/sys/fs/overflowgid
and
/proc/sys/fs/overflowuid.
- /proc/sys/kernel/panic
-
This file gives read/write access to the kernel variable
panic_timeout.
If this is zero, the kernel will loop on a panic; if nonzero,
it indicates that the kernel should autoreboot after this number
of seconds.
When you use the
software watchdog device driver, the recommended setting is 60.
- /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
-
This file controls the kernel's behavior when an oops
or BUG is encountered.
If this file contains 0, then the system
tries to continue operation.
If it contains 1, then the system
delays a few seconds (to give klogd time to record the oops output)
and then panics.
If the
/proc/sys/kernel/panic
file is also nonzero, then the machine will be rebooted.
- /proc/sys/kernel/pid_max (since Linux 2.5.34)
-
This file specifies the value at which PIDs wrap around
(i.e., the value in this file is one greater than the maximum PID).
PIDs greater than this value are not allocated;
thus, the value in this file also acts as a system-wide limit
on the total number of processes and threads.
The default value for this file, 32768,
results in the same range of PIDs as on earlier kernels.
On 32-bit platforms, 32768 is the maximum value for
pid_max.
On 64-bit systems,
pid_max
can be set to any value up to 2^22
(PID_MAX_LIMIT,
approximately 4 million).
- /proc/sys/kernel/powersave-nap (PowerPC only)
-
This file contains a flag.
If set, Linux-PPC will use the "nap" mode of
powersaving,
otherwise the "doze" mode will be used.
- /proc/sys/kernel/printk
-
See
syslog(2).
- /proc/sys/kernel/pty (since Linux 2.6.4)
-
This directory contains two files relating to the number of UNIX 98
pseudoterminals (see
pts(4))
on the system.
- /proc/sys/kernel/pty/max
-
This file defines the maximum number of pseudoterminals.
- /proc/sys/kernel/pty/nr
-
This read-only file
indicates how many pseudoterminals are currently in use.
- /proc/sys/kernel/random
-
This directory
contains various parameters controlling the operation of the file
/dev/random.
See
random(4)
for further information.
- /proc/sys/kernel/random/uuid (since Linux 2.4)
-
Each read from this read-only file returns a randomly generated 128-bit UUID,
as a string in the standard UUID format.
- /proc/sys/kernel/real-root-dev
-
This file is documented in the Linux kernel source file
Documentation/initrd.txt.
- /proc/sys/kernel/reboot-cmd (Sparc only)
-
This file seems to be a way to give an argument to the SPARC
ROM/Flash boot loader.
Maybe to tell it what to do after
rebooting?
- /proc/sys/kernel/rtsig-max
-
(Only in kernels up to and including 2.6.7; see
setrlimit(2))
This file can be used to tune the maximum number
of POSIX real-time (queued) signals that can be outstanding
in the system.
- /proc/sys/kernel/rtsig-nr
-
(Only in kernels up to and including 2.6.7.)
This file shows the number POSIX real-time signals currently queued.
- /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
-
See
sched_rr_get_interval(2).
- /proc/sys/kernel/sched_rt_period_us (Since Linux 2.6.25)
-
See
sched(7).
- /proc/sys/kernel/sched_rt_runtime_us (Since Linux 2.6.25)
-
See
sched(7).
- /proc/sys/kernel/sem (since Linux 2.4)
-
This file contains 4 numbers defining limits for System V IPC semaphores.
These fields are, in order:
-
- SEMMSL
-
The maximum semaphores per semaphore set.
- SEMMNS
-
A system-wide limit on the number of semaphores in all semaphore sets.
- SEMOPM
-
The maximum number of operations that may be specified in a
semop(2)
call.
- SEMMNI
-
A system-wide limit on the maximum number of semaphore identifiers.
- /proc/sys/kernel/sg-big-buff
-
This file
shows the size of the generic SCSI device (sg) buffer.
You can't tune it just yet, but you could change it at
compile time by editing
include/scsi/sg.h
and changing
the value of
SG_BIG_BUFF.
However, there shouldn't be any reason to change this value.
- /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
-
If this file is set to 1, all System V shared memory segments will
be marked for destruction as soon as the number of attached processes
falls to zero;
in other words, it is no longer possible to create shared memory segments
that exist independently of any attached process.
-
The effect is as though a
shmctl(2)
IPC_RMID
is performed on all existing segments as well as all segments
created in the future (until this file is reset to 0).
Note that existing segments that are attached to no process will be
immediately destroyed when this file is set to 1.
Setting this option will also destroy segments that were created,
but never attached,
upon termination of the process that created the segment with
shmget(2).
-
Setting this file to 1 provides a way of ensuring that
all System V shared memory segments are counted against the
resource usage and resource limits (see the description of
RLIMIT_AS
in
getrlimit(2))
of at least one process.
-
Because setting this file to 1 produces behavior that is nonstandard
and could also break existing applications,
the default value in this file is 0.
Only set this file to 1 if you have a good understanding
of the semantics of the applications using
System V shared memory on your system.
- /proc/sys/kernel/shmall (since Linux 2.2)
-
This file
contains the system-wide limit on the total number of pages of
System V shared memory.
- /proc/sys/kernel/shmmax (since Linux 2.2)
-
This file
can be used to query and set the run-time limit
on the maximum (System V IPC) shared memory segment size that can be
created.
Shared memory segments up to 1GB are now supported in the
kernel.
This value defaults to
SHMMAX.
- /proc/sys/kernel/shmmni (since Linux 2.4)
-
This file
specifies the system-wide maximum number of System V shared memory
segments that can be created.
- /proc/sys/kernel/sysrq
-
This file controls the functions allowed to be invoked by the SysRq key.
By default,
the file contains 1 meaning that every possible SysRq request is allowed
(in older kernel versions, SysRq was disabled by default,
and you were required to specifically enable it at run-time,
but this is not the case any more).
Possible values in this file are:
0 - disable sysrq completely
1 - enable all functions of sysrq
>1 - bit mask of allowed sysrq functions, as follows:
2 - enable control of console logging level
4 - enable control of keyboard (SAK, unraw)
8 - enable debugging dumps of processes etc.
16 - enable sync command
32 - enable remount read-only
64 - enable signaling of processes (term, kill, oom-kill)
128 - allow reboot/poweroff
256 - allow nicing of all real-time tasks
This file is present only if the
CONFIG_MAGIC_SYSRQ
kernel configuration option is enabled.
For further details see the Linux kernel source file
Documentation/sysrq.txt.
- /proc/sys/kernel/version
-
This file contains a string like:
#5 Wed Feb 25 21:49:24 MET 1998
The "#5" means that
this is the fifth kernel built from this source base and the
date behind it indicates the time the kernel was built.
- /proc/sys/kernel/threads-max (since Linux 2.3.11)
-
This file specifies the system-wide limit on the number of
threads (tasks) that can be created on the system.
- /proc/sys/kernel/zero-paged (PowerPC only)
-
This file
contains a flag.
When enabled (nonzero), Linux-PPC will pre-zero pages in
the idle loop, possibly speeding up get_free_pages.
- /proc/sys/net
-
This directory contains networking stuff.
Explanations for some of the files under this directory can be found in
tcp(7)
and
ip(7).
- /proc/sys/net/core/somaxconn
-
This file defines a ceiling value for the
backlog
argument of
listen(2);
see the
listen(2)
manual page for details.
- /proc/sys/proc
-
This directory may be empty.
- /proc/sys/sunrpc
-
This directory supports Sun remote procedure call for network filesystem
(NFS).
On some systems, it is not present.
- /proc/sys/vm
-
This directory contains files for memory management tuning, buffer and
cache management.
- /proc/sys/vm/drop_caches (since Linux 2.6.16)
-
Writing to this file causes the kernel to drop clean caches, dentries, and
inodes from memory, causing that memory to become free.
This can be useful for memory management testing and
performing reproducible filesystem benchmarks.
Because writing to this file causes the benefits of caching to be lost,
it can degrade overall system performance.
To free pagecache, use:
echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes, use:
echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries and inodes, use:
echo 3 > /proc/sys/vm/drop_caches
Because writing to this file is a nondestructive operation and dirty objects
are not freeable, the
user should run
sync(1)
first.
- /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
-
If nonzero, this disables the new 32-bit memory-mapping layout;
the kernel will use the legacy (2.4) layout for all processes.
- /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
-
Control how to kill processes when an uncorrected memory error
(typically a 2-bit error in a memory module)
that cannot be handled by the kernel
is detected in the background by hardware.
In some cases (like the page still having a valid copy on disk),
the kernel will handle the failure
transparently without affecting any applications.
But if there is no other up-to-date copy of the data,
it will kill processes to prevent any data corruptions from propagating.
The file has one of the following values:
-
- 1:
-
Kill all processes that have the corrupted-and-not-reloadable page mapped
as soon as the corruption is detected.
Note this is not supported for a few types of pages, like kernel internally
allocated data or the swap cache, but works for the majority of user pages.
- 0:
-
Only unmap the corrupted page from all processes and kill only a process
that tries to access it.
-
The kill is performed using a
SIGBUS
signal with
si_code
set to
BUS_MCEERR_AO.
Processes can handle this if they want to; see
sigaction(2)
for more details.
This feature is active only on architectures/platforms with advanced machine
check handling and depends on the hardware capabilities.
Applications can override the
memory_failure_early_kill
setting individually with the
prctl(2)
PR_MCE_KILL
operation.
-
Only present if the kernel was configured with
CONFIG_MEMORY_FAILURE.
- /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
-
Enable memory failure recovery (when supported by the platform)
-
- 1:
-
Attempt recovery.
- 0:
-
Always panic on a memory failure.
-
Only present if the kernel was configured with
CONFIG_MEMORY_FAILURE.
- /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
-
Enables a system-wide task dump (excluding kernel threads) to be
produced when the kernel performs an OOM-killing.
The dump includes the following information
for each task (thread, process):
thread ID, real user ID, thread group ID (process ID),
virtual memory size, resident set size,
the CPU that the task is scheduled on,
oom_adj score (see the description of
/proc/[pid]/oom_adj),
and command name.
This is helpful to determine why the OOM-killer was invoked
and to identify the rogue task that caused it.
If this contains the value zero, this information is suppressed.
On very large systems with thousands of tasks,
it may not be feasible to dump the memory state information for each one.
Such systems should not be forced to incur a performance penalty in
OOM situations when the information may not be desired.
If this is set to nonzero, this information is shown whenever the
OOM-killer actually kills a memory-hogging task.
The default value is 0.
- /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
-
This enables or disables killing the OOM-triggering task in
out-of-memory situations.
If this is set to zero, the OOM-killer will scan through the entire
tasklist and select a task based on heuristics to kill.
This normally selects a rogue memory-hogging task that
frees up a large amount of memory when killed.
If this is set to nonzero, the OOM-killer simply kills the task that
triggered the out-of-memory condition.
This avoids a possibly expensive tasklist scan.
If
/proc/sys/vm/panic_on_oom
is nonzero, it takes precedence over whatever value is used in
/proc/sys/vm/oom_kill_allocating_task.
The default value is 0.
- /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
-
This writable file provides an alternative to
/proc/sys/vm/overcommit_ratio
for controlling the
CommitLimit
when
/proc/sys/vm/overcommit_memory
has the value 2.
It allows the amount of memory overcommitting to be specified as
an absolute value (in kB),
rather than as a percentage, as is done with
overcommit_ratio.
This allows for finer-grained control of
CommitLimit
on systems with extremely large memory sizes.
Only one of
overcommit_kbytes
or
overcommit_ratio
can have an effect:
if
overcommit_kbytes
has a nonzero value, then it is used to calculate
CommitLimit,
otherwise
overcommit_ratio
is used.
Writing a value to either of these files causes the
value in the other file to be set to zero.
- /proc/sys/vm/overcommit_memory
-
This file contains the kernel virtual memory accounting mode.
Values are:
-
-
0: heuristic overcommit (this is the default)
1: always overcommit, never check
2: always check, never overcommit
-
In mode 0, calls of
mmap(2)
with
MAP_NORESERVE
are not checked, and the default check is very weak,
leading to the risk of getting a process "OOM-killed".
Under Linux 2.4, any nonzero value implies mode 1.
In mode 2 (available since Linux 2.6), the total virtual address space
that can be allocated
(CommitLimit
in
/proc/meminfo)
is calculated as
CommitLimit = (total_RAM - total_huge_TLB) *
overcommit_ratio / 100 + total_swap
where:
-
- *
-
total_RAM
is the total amount of RAM on the system;
- *
-
total_huge_TLB
is the amount of memory set aside for huge pages;
- *
-
overcommit_ratio
is the value in
/proc/sys/vm/overcommit_ratio;
and
- *
-
total_swap
is the amount of swap space.
-
For example, on a system with 16GB of physical RAM, 16GB
of swap, no space dedicated to huge pages, and an
overcommit_ratio
of 50, this formula yields a
CommitLimit
of 24GB.
Since Linux 3.14, if the value in
/proc/sys/vm/overcommit_kbytes
is nonzero, then
CommitLimit
is instead calculated as:
CommitLimit = overcommit_kbytes + total_swap
- /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
-
This writable file defines a percentage by which memory
can be overcommitted.
The default value in the file is 50.
See the description of
/proc/sys/vm/overcommit_memory.
- /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
-
This enables or disables a kernel panic in
an out-of-memory situation.
If this file is set to the value 0,
the kernel's OOM-killer will kill some rogue process.
Usually, the OOM-killer is able to kill a rogue process and the
system will survive.
If this file is set to the value 1,
then the kernel normally panics when out-of-memory happens.
However, if a process limits allocations to certain nodes
using memory policies
(mbind(2)
MPOL_BIND)
or cpusets
(cpuset(7))
and those nodes reach memory exhaustion status,
one process may be killed by the OOM-killer.
No panic occurs in this case:
because other nodes' memory may be free,
this means the system as a whole may not have reached
an out-of-memory situation yet.
If this file is set to the value 2,
the kernel always panics when an out-of-memory condition occurs.
The default value is 0.
1 and 2 are for failover of clustering.
Select either according to your policy of failover.
- /proc/sys/vm/swappiness
-
The value in this file controls how aggressively the kernel will swap
memory pages.
Higher values increase aggressiveness, lower values
decrease aggressiveness.
The default value is 60.
- /proc/sysrq-trigger (since Linux 2.4.21)
-
Writing a character to this file triggers the same SysRq function as
typing ALT-SysRq-<character> (see the description of
/proc/sys/kernel/sysrq).
This file is normally writable only by
root.
For further details see the Linux kernel source file
Documentation/sysrq.txt.
- /proc/sysvipc
-
Subdirectory containing the pseudo-files
msg, sem and shm.
These files list the System V Interprocess Communication (IPC) objects
(respectively: message queues, semaphores, and shared memory)
that currently exist on the system,
providing similar information to that available via
ipcs(1).
These files have headers and are formatted (one IPC object per line)
for easy understanding.
svipc(7)
provides further background on the information shown by these files.
- /proc/timer_list (since Linux 2.6.21)
-
This read-only file exposes a list of all currently pending
(high-resolution) timers,
all clock-event sources, and their parameters in a human-readable form.
- /proc/timer_stats (since Linux 2.6.21)
-
This is a debugging facility to make timer (ab)use in a Linux
system visible to kernel and user-space developers.
It can be used by kernel and user-space developers to verify that
their code does not make undue use of timers.
The goal is to avoid unnecessary wakeups,
thereby optimizing power consumption.
If enabled in the kernel
(CONFIG_TIMER_STATS),
but not used,
it has almost zero runtime overhead and a relatively small
data-structure overhead.
Even if collection is enabled at runtime, overhead is low:
all the locking is per-CPU and lookup is hashed.
The
/proc/timer_stats
file is used both to control sampling facility and to read out the
sampled information.
The timer_stats functionality is inactive on bootup.
A sampling period can be started using the following command:
# echo 1 > /proc/timer_stats
The following command stops a sampling period:
# echo 0 > /proc/timer_stats
The statistics can be retrieved by:
$ cat /proc/timer_stats
While sampling is enabled, each readout from
/proc/timer_stats
will see
newly updated statistics.
Once sampling is disabled, the sampled information
is kept until a new sample period is started.
This allows multiple readouts.
Sample output from
/proc/timer_stats:
$ cat /proc/timer_stats
Timer Stats Version: v0.3
Sample period: 1.764 s
Collection: active
255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer)
71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer)
58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer)
4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn)
17, 7 rcu_sched rcu_gp_kthread (process_timeout)
...
1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn)
1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn)
1029 total events, 583.333 events/sec
-
The output columns are:
-
- *
-
a count of the number of events,
optionally (since Linux 2.6.23) followed by the letter 'D'
if this is a deferrable timer;
- *
-
the PID of the process that initialized the timer;
- *
-
the name of the process that initialized the timer;
- *
-
the function where the timer was initialized; and
- *
-
(in parentheses)
the callback function that is associated with the timer.
- /proc/tty
-
Subdirectory containing the pseudo-files and subdirectories for
tty drivers and line disciplines.
- /proc/uptime
-
This file contains two numbers: the uptime of the system (seconds),
and the amount of time spent in idle process (seconds).
- /proc/version
-
This string identifies the kernel version that is currently running.
It includes the contents of
/proc/sys/kernel/ostype,
/proc/sys/kernel/osrelease
and
/proc/sys/kernel/version.
For example:
Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994
- /proc/vmstat (since Linux 2.6)
-
This file displays various virtual memory statistics.
- /proc/zoneinfo (since Linux 2.6.13)
-
This file display information about memory zones.
This is useful for analyzing virtual memory behavior.
This manual page is incomplete, possibly inaccurate, and is the kind
of thing that needs to be updated very often.