SW Components : OS, Sub-Systems (Softwares, Terminal, IPC, Pipes, Sockets, Kernel, Microkernel)
HW Components : ROM, RAM, CPU, GPU, MOTHERBOARD, PCI_DEVICES, KEYBOARD, BATTERY, SCREEN
RHEL OFFICIAL TOPICS 1-Administration webconsole system roles settings network subscriptions systemd security users kernel recovery troubleshoot 2-software packages 11-chrony ntp 12-openSSH 13-remote logging 14-logging system role 15-python 16-php 17-langpacks 18-tcl tk
man hier Description of the file system hierarchy
/ Root Directory /bin Essential user command binaries (for use by all users) /boot Static files of the boot loader, only used at system startup /dev Device files, links to your hardware devices like /dev/sound, /dev/input/js0 (joystick) /etc Host-specific system configuration /home User home directories. This is where you save your personal files /lib Essential shared libraries and kernel modules /mnt Mount point for a temporarily mounted filesystem like /mnt/cdrom /opt Add-on application software packages /usr Major section of the filesystem, shareable, read-only data bbetween various FHS-compliant hosts and must not be written to. /var Variable data files. This includes spool directories and files, administrative and logging data, and transient and temporary files. /proc System information stored in memory mirrored as file
SYSTEM INFORMATION uname -a Get the kernel version (and BSD version) lsb_release -a Full release info of any LSB distribution cat /etc/SuSE-release Get SuSE version cat /etc/debian_version Get Debian version cat /etc/issue Get issue nb uptime Show how long the system has been running + load hostname system's host name hostname -i Display the IP address of the host. (Linux only) last reboot Show system reboot history dmesg Detected hardware and boot messages lsdev information about installed hardware dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8 Read BIOS Linux cat /proc/cpuinfo CPU model cat /proc/meminfo Hardware memory grep MemTotal /proc/meminfo Display the physical memory watch -n1 'cat /proc/interrupts' Watch changeable interrupts continuously free -m Used and free memory (-m for MB) cat /proc/devices Configured devices lspci -tv Show PCI devices lsusb -tv Show USB devices lshal Show a list of all devices with their properties dmidecode Show DMI/SMBIOS: hw info from the BIOS FreeBSD sysctl hw.model CPU model sysctl hw Gives a lot of hardware information sysctl hw.ncpu number of active CPUs installed sysctl vm Memory usage sysctl hw.realmem Hardware memory sysctl -a | grep mem Kernel memory settings and info sysctl dev Configured devices pciconf -l -cv Show PCI devices usbdevs -v Show USB devices atacontrol list Show ATA devices camcontrol devlist -v Show SCSI devices Load, statistics and messages top display and update the top cpu processes mpstat 1 display processors related statistics vmstat 2 display virtual memory statistics iostat 2 display I/O statistics (2 s intervals) systat -vmstat 1 BSD summary of system statistics (1 s intervals) systat -tcp 1 BSD tcp connections (try also -ip) systat -netstat 1 BSD active network connections systat -ifstat 1 BSD network traffic through active interfaces systat -iostat 1 BSD CPU and and disk throughput tail -n 500 /var/log/messages Last 500 kernel/syslog messages tail /var/log/warn System warnings messages see syslog.conf Users id Show the active user id with login and group last Show last logins on the system who Show who is logged on the system groupadd admin Add group "admin" and user colin (Linux/Solaris) useradd -c "Colin Barschel" -g admin -m colin usermod -a -G group user Add existing user to group (Debian) groupmod -A user group Add existing user to group (SuSE) userdel colin Delete user colin (Linux/Solaris) adduser joe FreeBSD add user joe (interactive) rmuser joe FreeBSD delete user joe (interactive) pw groupadd admin Use pw on FreeBSD pw groupmod admin -m newmember Add a new member to a group pw useradd colin -c "Colin Barschel" -g admin -m -s /bin/tcsh pw userdel colin; pw groupdel admin Encrypted passwords are stored in /etc/shadow for Linux and Solaris and /etc/master.passwd on FreeBSD. If the master.passwd is modified manually (say to delete a password), run pwd_mkdb -p master.passwd to rebuild the database. To temporarily prevent logins system wide (for all users but root) use nologin. The message in nologin will be displayed (might not work with ssh pre-shared keys). echo "Sorry no login now" > /etc/nologin (Linux) echo "Sorry no login now" > /var/run/nologin (FreeBSD) Limits Some application require higher limits on open files and sockets (like a proxy web server, database). The default limits are usually too low. Linux Per shell/script The shell limits are governed by ulimit. The status is checked with ulimit -a. For example to change the open files limit from 1024 to 10240 do: ulimit -n 10240 This is only valid within the shell The ulimit command can be used in a script to change the limits for the script only. Per user/process Login users and applications can be configured in /etc/security/limits.conf. For example: cat /etc/security/limits.conf * hard nproc 250 Limit user processes asterisk hard nofile 409600 Limit application open files System wide Kernel limits are set with sysctl. Permanent limits are set in /etc/sysctl.conf. sysctl -a View all system limits sysctl fs.file-max View max open files limit sysctl fs.file-max=102400 Change max open files limit echo "1024 50000" > /proc/sys/net/ipv4/ip_local_port_range port range cat /etc/sysctl.conf fs.file-max=102400 Permanent entry in sysctl.conf cat /proc/sys/fs/file-nr How many file descriptors are in use FreeBSD Per shell/script Use the command limits in csh or tcsh or as in Linux, use ulimit in an sh or bash shell. Per user/process The default limits on login are set in /etc/login.conf. An unlimited value is still limited by the system maximal value. System wide Kernel limits are also set with sysctl. Permanent limits are set in /etc/sysctl.conf or /boot/loader.conf. The syntax is the same as Linux but the keys are different. sysctl -a View all system limits sysctl kern.maxfiles=XXXX maximum number of file descriptors kern.ipc.nmbclusters=32768 Permanent entry in /etc/sysctl.conf kern.maxfiles=65536 Typical values for Squid kern.maxfilesperproc=32768 kern.ipc.somaxconn=8192 TCP queue. Better for apache/sendmail sysctl kern.openfiles How many file descriptors are in use sysctl kern.ipc.numopensockets How many open sockets are in use sysctl net.inet.ip.portrange.last=50000 Default is 1024-5000 netstat -m network memory buffers statistics See The FreeBSD handbook Chapter 11 for details. Solaris The following values in /etc/system will increase the maximum file descriptors per proc: set rlim_fd_max = 4096 Hard limit on file descriptors for a single proc set rlim_fd_cur = 1024 Soft limit on file descriptors for a single proc Runlevels Linux Once booted, the kernel starts init which then starts rc which starts all scripts belonging to a runlevel. The scripts are stored in /etc/init.d and are linked into /etc/rc.d/rcN.d with N the runlevel number. The default runlevel is configured in /etc/inittab. It is usually 3 or 5: grep default: /etc/inittab id:3:initdefault: The actual runlevel can be changed with init. For example to go from 3 to 5: init 5 Enters runlevel 5 0 Shutdown and halt 1 Single-User mode (also S) 2 Multi-user without network 3 Multi-user with network 5 Multi-user with X 6 Reboot Use chkconfig to configure the programs that will be started at boot in a runlevel. chkconfig --list List all init scripts chkconfig --list sshd Report the status of sshd chkconfig sshd --level 35 on Configure sshd for levels 3 and 5 chkconfig sshd off Disable sshd for all runlevels Debian and Debian based distributions like Ubuntu or Knoppix use the command update-rc.d to manage the runlevels scripts. Default is to start in 2,3,4 and 5 and shutdown in 0,1 and 6. update-rc.d sshd defaults Activate sshd with the default runlevels update-rc.d sshd start 20 2 3 4 5 . stop 20 0 1 6 . With explicit arguments update-rc.d -f sshd remove Disable sshd for all runlevels shutdown -h now (or poweroff) Shutdown and halt the system FreeBSD The BSD boot approach is different from the SysV, there are no runlevels. The final boot state (single user, with or without X) is configured in /etc/ttys. All OS scripts are located in /etc/rc.d/ and in /usr/local/etc/rc.d/ for third-party applications. The activation of the service is configured in /etc/rc.conf and /etc/rc.conf.local. The default behavior is configured in /etc/defaults/rc.conf. The scripts responds at least to start|stop|status. /etc/rc.d/sshd status sshd is running as pid 552. shutdown now Go into single-user mode exit Go back to multi-user mode shutdown -p now Shutdown and halt the system shutdown -r now Reboot The process init can also be used to reach one of the following states level. For example init 6 for reboot. 0 Halt and turn the power off (signal USR2) 1 Go to single-user mode (signal TERM) 6 Reboot the machine (signal INT) c Block further logins (signal TSTP) q Rescan the ttys(5) file (signal HUP) Windows Start and stop a service with either the service name or "service description" (shown in the Services Control Panel) as follows: net stop WSearch net start WSearch start search service net stop "Windows Search" net start "Windows Search" same as above using descr. Reset root password Linux method 1 At the boot loader (lilo or grub), enter the following boot option: init=/bin/sh The kernel will mount the root partition and init will start the bourne shell instead of rc and then a runlevel. Use the command passwd at the prompt to change the password and then reboot. Forget the single user mode as you need the password for that. If, after booting, the root partition is mounted read only, remount it rw: mount -o remount,rw / passwd or delete the root password (/etc/shadow) sync; mount -o remount,ro / sync before to remount read only reboot FreeBSD method 1 On FreeBSD, boot in single user mode, remount / rw and use passwd. You can select the single user mode on the boot menu (option 4) which is displayed for 10 seconds at startup. The single user mode will give you a root shell on the / partition. mount -u /; mount -a will mount / rw passwd reboot Unixes and FreeBSD and Linux method 2 Other Unixes might not let you go away with the simple init trick. The solution is to mount the root partition from an other OS (like a rescue CD) and change the password on the disk. Boot a live CD or installation CD into a rescue mode which will give you a shell. Find the root partition with fdisk e.g. fdisk /dev/sda Mount it and use chroot: mount -o rw /dev/ad4s3a /mnt chroot /mnt chroot into /mnt passwd reboot Kernel modules Linux lsmod List all modules loaded in the kernel modprobe isdn To load a module (here isdn) FreeBSD kldstat List all modules loaded in the kernel kldload crypto To load a module (here crypto) Compile Kernel Linux cd /usr/src/linux make mrproper Clean everything, including config files make oldconfig Reuse the old .config if existent make menuconfig or xconfig (Qt) or gconfig (GTK) make Create a compressed kernel image make modules Compile the modules make modules_install Install the modules make install Install the kernel reboot FreeBSD Optionally update the source tree (in /usr/src) with csup (as of FreeBSD 6.2 or later): csup supfile> I use the following supfile: *default host=cvsup5.FreeBSD.org www.freebsd.org/handbook/cvsup.html#CVSUP-MIRRORS *default prefix=/usr *default base=/var/db *default release=cvs delete tag=RELENG_7 src-all To modify and rebuild the kernel, copy the generic configuration file to a new name and edit it as needed (you can also edit the file GENERIC directly). To restart the build after an interruption, add the option NO_CLEAN=YES to the make command to avoid cleaning the objects already build. cd /usr/src/sys/i386/conf/ cp GENERIC MYKERNEL cd /usr/src make buildkernel KERNCONF=MYKERNEL make installkernel KERNCONF=MYKERNEL To rebuild the full OS: make buildworld Build the full OS but not the kernel make buildkernel Use KERNCONF as above if appropriate make installkernel reboot mergemaster -p Compares only files known to be essential make installworld mergemaster -i -U Update all configurations and other files reboot For small changes in the source you can use NO_CLEAN=yes to avoid rebuilding the whole tree. make buildworld NO_CLEAN=yes Don't delete the old objects make buildkernel KERNCONF=MYKERNEL NO_CLEAN=yes Repair grub So you broke grub? Boot from a live cd, [find your linux partition under /dev and use fdisk to find the linux partion] mount the linux partition, add /proc and /dev and use grub-install /dev/xyz. Suppose linux lies on /dev/sda6: mount /dev/sda6 /mnt mount the linux partition on /mnt mount --bind /proc /mnt/proc mount the proc subsystem into /mnt mount --bind /dev /mnt/dev mount the devices into /mnt chroot /mnt change root to the linux partition grub-install /dev/sda reinstall grub with your old settings Processes Listing | Priority | Background/Foreground | Top | Kill Listing and PIDs Each process has a unique number, the PID. A list of all running process is retrieved with ps. ps -auxefw Extensive list of all running process However more typical usage is with a pipe or with pgrep (for OS X install proctools from MacPorts): ps axww | grep cron 586 ?? Is 0:01.48 /usr/sbin/cron -s ps axjf All processes in a tree format (Linux) ps aux | grep 'ss[h]' Find all ssh pids without the grep pid pgrep -l sshd Find the PIDs of processes by (part of) name echo $$ The PID of your shell fuser -va 22/tcp List processes using port 22 (Linux) pmap PID Memory map of process (hunt memory leaks) (Linux) fuser -va /home List processes accessing the /home partition strace df Trace system calls and signals truss df same as above on FreeBSD/Solaris/Unixware Priority Change the priority of a running process with renice. Negative numbers have a higher priority, the lowest is -20 and "nice" have a positive value. renice -5 586 Stronger priority 586: old priority 0, new priority -5 Start the process with a defined priority with nice. Positive is "nice" or weak, negative is strong scheduling priority. Make sure you know if /usr/bin/nice or the shell built-in is used (check with which nice). nice -n -5 top Stronger priority (/usr/bin/nice) nice -n 5 top Weaker priority (/usr/bin/nice) nice +5 top tcsh builtin nice (same as above!) While nice changes the CPU scheduler, an other useful command ionice will schedule the disk IO. This is very useful for intensive IO application (e.g. compiling). You can select a class (idle - best effort - real time), the man page is short and well explained. ionice c3 -p123 set idle class for pid 123 (Linux only) ionice -c2 -n0 firefox Run firefox with best effort and high priority ionice -c3 -p$$ Set the actual shell to idle priority The last command is very useful to compile (or debug) a large project. Every command launched from this shell will have a lover priority. $$ is your shell pid (try echo $$). FreeBSD uses idprio/rtprio (0 = max priority, 31 = most idle): idprio 31 make compile in the lowest priority idprio 31 -1234 set PID 1234 with lowest priority idprio -t -1234 -t removes any real time/idle priority Background/Foreground When started from a shell, processes can be brought in the background and back to the foreground with [Ctrl]-[Z] (^Z), bg and fg. List the processes with jobs. ping cb.vu > ping.log ^Z ping is suspended (stopped) with [Ctrl]-[Z] bg put in background and continues running jobs -l List processes in background [1] - 36232 Running ping cb.vu > ping.log [2] + 36233 Suspended (tty output) top fg %2 Bring process 2 back in foreground Use nohup to start a process which has to keep running when the shell is closed (immune to hangups). nohup ping -i 60 > ping.log & Top The program top displays running information of processes. See also the program htop from htop.sourceforge.net (a more powerful version of top) which runs on Linux and FreeBSD (ports/sysutils/htop/). While top is running press the key h for a help overview. Useful keys are: u [user name] To display only the processes belonging to the user. Use + or blank to see all users k [pid] Kill the process with pid. 1 To display all processors statistics (Linux only) R Toggle normal/reverse sort. Signals/Kill Terminate or send a signal with kill or killall. ping -i 60 cb.vu > ping.log & [1] 4712 kill -s TERM 4712 same as kill -15 4712 killall -1 httpd Kill HUP processes by exact name pkill -9 http Kill TERM processes by (part of) name pkill -TERM -u www Kill TERM processes owned by www fuser -k -TERM -m /home Kill every process accessing /home (to umount) Important signals are: 1 HUP (hang up) 2 INT (interrupt) 3 QUIT (quit) 9 KILL (non-catchable, non-ignorable kill) 15 TERM (software termination signal) File System Disk info | Boot | Disk usage | Opened files | Mount/remount | Mount SMB | Mount image | Burn ISO | Create image | Memory disk | Disk performance Permissions Change permission and ownership with chmod and chown. The default umask can be changed for all users in /etc/profile for Linux or /etc/login.conf for FreeBSD. The default umask is usually 022. The umask is subtracted from 777, thus umask 022 results in a permission 0f 755. 1 --x execute Mode 764 = exec/read/write | read/write | read 2 -w- write For: |-- Owner --| |- Group-| |Oth| 4 r-- read ugo=a u=user, g=group, o=others, a=everyone chmod [OPTION] MODE[,MODE] FILE MODE is of the form [ugoa]*([-+=]([rwxXst])) chmod 640 /var/log/maillog Restrict the log -rw-r----- chmod u=rw,g=r,o= /var/log/maillog Same as above chmod -R o-r /home/* Recursive remove other readable for all users chmod u+s /path/to/prog Set SUID bit on executable (know what you do!) find / -perm -u+s -print Find all programs with the SUID bit chown user:group /path/to/file Change the user and group ownership of a file chgrp group /path/to/file Change the group ownership of a file chmod 640 `find ./ -type f -print` Change permissions to 640 for all files chmod 751 `find ./ -type d -print` Change permissions to 751 for all directories Disk information diskinfo -v /dev/ad2 information about disk (sector/size) FreeBSD hdparm -I /dev/sda information about the IDE/ATA disk (Linux) fdisk /dev/ad2 Display and manipulate the partition table smartctl -a /dev/ad2 Display the disk SMART info Boot FreeBSD To boot an old kernel if the new kernel doesn't boot, stop the boot at during the count down. unload load kernel.old boot System mount points/Disk usage mount | column -t Show mounted file-systems on the system df display free disk space and mounted devices cat /proc/partitions Show all registered partitions (Linux) Disk usage du -sh * Directory sizes as listing du -csh Total directory size of the current directory du -ks * | sort -n -r Sort everything by size in kilobytes ls -lSr Show files, biggest last Who has which files opened This is useful to find out which file is blocking a partition which has to be unmounted and gives a typical error of: umount /home/ umount: unmount of /home umount impossible because a file is locking home failed: Device busy FreeBSD and most Unixes fstat -f /home for a mount point fstat -p PID for an application with PID fstat -u user for a user name Find opened log file (or other opened files), say for Xorg: ps ax | grep Xorg | awk '{print $1}' 1252 fstat -p 1252 USER CMD PID FD MOUNT INUM MODE SZ|DV R/W root Xorg 1252 root / 2 drwxr-xr-x 512 r root Xorg 1252 text /usr 216016 -rws--x--x 1679848 r root Xorg 1252 0 /var 212042 -rw-r--r-- 56987 w The file with inum 212042 is the only file in /var: find -x /var -inum 212042 /var/log/Xorg.0.log Linux Find opened files on a mount point with fuser or lsof: fuser -m /home List processes accessing /home lsof /home COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME tcsh 29029 eedcoba cwd DIR 0,18 12288 1048587 /home/eedcoba (guam:/home) lsof 29140 eedcoba cwd DIR 0,18 12288 1048587 /home/eedcoba (guam:/home) About an application: ps ax | grep Xorg | awk '{print $1}' 3324 lsof -p 3324 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME Xorg 3324 root 0w REG 8,6 56296 12492 /var/log/Xorg.0.log About a single file: lsof /var/log/Xorg.0.log COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME Xorg 3324 root 0w REG 8,6 56296 12492 /var/log/Xorg.0.log Mount/remount a file system For example the cdrom. If listed in /etc/fstab: mount /cdrom Or find the device in /dev/ or with dmesg FreeBSD mount -v -t cd9660 /dev/cd0c /mnt cdrom mount_cd9660 /dev/wcd0c /cdrom other method mount -v -t msdos /dev/fd0c /mnt floppy Entry in /etc/fstab: Device Mountpoint FStype Options Dump Pass# /dev/acd0 /cdrom cd9660 ro,noauto 0 0 To let users do it: sysctl vfs.usermount=1 Or insert the line "vfs.usermount=1" in /etc/sysctl.conf Linux mount -t auto /dev/cdrom /mnt/cdrom typical cdrom mount command mount /dev/hdc -t iso9660 -r /cdrom typical IDE mount /dev/scd0 -t iso9660 -r /cdrom typical SCSI cdrom mount /dev/sdc0 -t ntfs-3g /windows typical SCSI Entry in /etc/fstab: /dev/cdrom /media/cdrom subfs noauto,fs=cdfss,ro,procuid,nosuid,nodev,exec 0 0 Mount a FreeBSD partition with Linux Find the partition number containing with fdisk, this is usually the root partition, but it could be an other BSD slice too. If the FreeBSD has many slices, they are the one not listed in the fdisk table, but visible in /dev/sda* or /dev/hda*. fdisk /dev/sda Find the FreeBSD partition /dev/sda3 * 5357 7905 20474842+ a5 FreeBSD mount -t ufs -o ufstype=ufs2,ro /dev/sda3 /mnt /dev/sda10 = /tmp; /dev/sda11 /usr The other slices Remount Remount a device without unmounting it. Necessary for fsck for example mount -o remount,ro / Linux mount -o ro / FreeBSD Copy the raw data from a cdrom into an iso image: dd if=/dev/cd0c of=file.iso Add swap on-the-fly Suppose you need more swap (right now), say a 2GB file /swap2gb (Linux only). dd if=/dev/zero of=/swap2gb bs=1024k count=2000 mkswap /swap2gb create the swap area swapon /swap2gb activate the swap. It now in use swapoff /swap2gb when done deactivate the swap rm /swap2gb Mount an SMB share Suppose we want to access the SMB share myshare on the computer smbserver, the address as typed on a Windows PC is \\smbserver\myshare\. We mount on /mnt/smbshare. Warning> cifs wants an IP or DNS name, not a Windows name. Linux smbclient -U user -I <IP_ADDRESS> -L //smbshare/ List the shares mount -t smbfs -o username=winuser //smbserver/myshare /mnt/smbshare mount -t cifs -o username=winuser,password=winpwd //<IP_ADDRESS>/myshare /mnt/share Additionally with the package mount.cifs it is possible to store the credentials in a file, for example /home/user/.smb: username=winuser password=winpwd And mount as follow: mount -t cifs -o credentials=/home/user/.smb //<IP_ADDRESS>/myshare /mnt/smbshare FreeBSD Use -I to give the IP (or DNS name); smbserver is the Windows name. smbutil view -I <IP_ADDRESS> //winuser@smbserver List the shares mount_smbfs -I <IP_ADDRESS> //winuser@smbserver/myshare /mnt/smbshare Mount an image hdiutil mount image.iso OS X Linux loop-back mount -t iso9660 -o loop file.iso /mnt Mount a CD image mount -t ext3 -o loop file.img /mnt Mount an image with ext3 fs FreeBSD With memory device (do kldload md.ko if necessary): mdconfig -a -t vnode -f file.iso -u 0 mount -t cd9660 /dev/md0 /mnt umount /mnt; mdconfig -d -u 0 Cleanup the md device Or with virtual node: vnconfig /dev/vn0c file.iso; mount -t cd9660 /dev/vn0c /mnt umount /mnt; vnconfig -u /dev/vn0c Cleanup the vn device Solaris and FreeBSD with loop-back file interface or lofi: lofiadm -a file.iso mount -F hsfs -o ro /dev/lofi/1 /mnt umount /mnt; lofiadm -d /dev/lofi/1 Cleanup the lofi device Create and burn an ISO image This will copy the cd or DVD sector for sector. Without conv=notrunc, the image will be smaller if there is less content on the cd. See below and the dd examples. dd if=/dev/hdc of=/tmp/mycd.iso bs=2048 conv=notrunc Use mkisofs to create a CD/DVD image from files in a directory. To overcome the file names restrictions: -r enables the Rock Ridge extensions common to UNIX systems, -J enables Joliet extensions used by Microsoft systems. -L allows ISO9660 filenames to begin with a period. mkisofs -J -L -r -V TITLE -o imagefile.iso /path/to/dir hdiutil makehybrid -iso -joliet -o dir.iso dir/ OS X On FreeBSD, mkisofs is found in the ports in sysutils/cdrtools. Burn a CD/DVD ISO image FreeBSD FreeBSD does not enable DMA on ATAPI drives by default. DMA is enabled with the sysctl command and the arguments below, or with /boot/loader.conf with the following entries: hw.ata.ata_dma="1" hw.ata.atapi_dma="1" Use burncd with an ATAPI device (burncd is part of the base system) and cdrecord (in sysutils/cdrtools) with a SCSI drive. burncd -f /dev/acd0 data imagefile.iso fixate For ATAPI drive cdrecord -scanbus To find the burner device (like 1,0,0) cdrecord dev=1,0,0 imagefile.iso Linux Also use cdrecord with Linux as described above. Additionally it is possible to use the native ATAPI interface which is found with: cdrecord dev=ATAPI -scanbus And burn the CD/DVD as above. dvd+rw-tools The dvd+rw-tools package (FreeBSD: ports/sysutils/dvd+rw-tools) can do it all and includes growisofs to burn CDs or DVDs. The examples refer to the dvd device as /dev/dvd which could be a symlink to /dev/scd0 (typical scsi on Linux) or /dev/cd0 (typical FreeBSD) or /dev/rcd0c (typical NetBSD/OpenBSD character SCSI) or /dev/rdsk/c0t1d0s2 (Solaris example of a character SCSI/ATAPI CD-ROM device). There is a nice documentation with examples on the FreeBSD handbook chapter 18.7. -dvd-compat closes the disk growisofs -dvd-compat -Z /dev/dvd=imagefile.iso Burn existing iso image growisofs -dvd-compat -Z /dev/dvd -J -R /p/to/data Burn directly Convert a Nero .nrg file to .iso Nero simply adds a 300Kb header to a normal iso image. This can be trimmed with dd. dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300 Convert a bin/cue image to .iso The little bchunk program can do this. It is in the FreeBSD ports in sysutils/bchunk. bchunk imagefile.bin imagefile.cue imagefile.iso Create a file based image For example a partition of 1GB using the file /usr/vdisk.img. Here we use the vnode 0, but it could also be 1. FreeBSD dd if=/dev/random of=/usr/vdisk.img bs=1K count=1M mdconfig -a -t vnode -f /usr/vdisk.img -u 0 Creates device /dev/md1 bsdlabel -w /dev/md0 newfs /dev/md0c mount /dev/md0c /mnt umount /mnt; mdconfig -d -u 0; rm /usr/vdisk.img Cleanup the md device The file based image can be automatically mounted during boot with an entry in /etc/rc.conf and /etc/fstab. Test your setup with /etc/rc.d/mdconfig start (first delete the md0 device with mdconfig -d -u 0). Note however that this automatic setup will only work if the file image is NOT on the root partition. The reason is that the /etc/rc.d/mdconfig script is executed very early during boot and the root partition is still read-only. Images located outside the root partition will be mounted later with the script /etc/rc.d/mdconfig2. /boot/loader.conf: md_load="YES" /etc/rc.conf: mdconfig_md0="-t vnode -f /usr/vdisk.img" /usr is not on the root partition /etc/fstab: (The 0 0 at the end is important, it tell fsck to ignore this device, as is does not exist yet) /dev/md0 /usr/vdisk ufs rw 0 0 It is also possible to increase the size of the image afterward, say for example 300 MB larger. umount /mnt; mdconfig -d -u 0 dd if=/dev/zero bs=1m count=300 >> /usr/vdisk.img mdconfig -a -t vnode -f /usr/vdisk.img -u 0 growfs /dev/md0 mount /dev/md0c /mnt File partition is now 300 MB larger Linux dd if=/dev/zero of=/usr/vdisk.img bs=1024k count=1024 mkfs.ext3 /usr/vdisk.img mount -o loop /usr/vdisk.img /mnt umount /mnt; rm /usr/vdisk.img Cleanup Linux with losetup /dev/zero is much faster than urandom, but less secure for encryption. dd if=/dev/urandom of=/usr/vdisk.img bs=1024k count=1024 losetup /dev/loop0 /usr/vdisk.img Creates and associates /dev/loop0 mkfs.ext3 /dev/loop0 mount /dev/loop0 /mnt losetup -a Check used loops umount /mnt losetup -d /dev/loop0 Detach rm /usr/vdisk.img Create a memory file system A memory based file system is very fast for heavy IO application. How to create a 64 MB partition mounted on /memdisk: FreeBSD mount_mfs -o rw -s 64M md /memdisk umount /memdisk; mdconfig -d -u 0 Cleanup the md device md /memdisk mfs rw,-s64M 0 0 /etc/fstab entry Linux mount -t tmpfs -osize=64m tmpfs /memdisk Disk performance Read and write a 1 GB file on partition ad4s3c (/home) time dd if=/dev/ad4s3c of=/dev/null bs=1024k count=1000 time dd if=/dev/zero bs=1024k count=1000 of=/home/1Gb.file hdparm -tT /dev/hda Linux only Network Routing | Additional IP | Change MAC | Ports | Firewall | IP Forward | NAT | DNS | DHCP | Traffic | QoS | NIS | Netcat Debugging (See also Traffic analysis) Linux ethtool eth0 Show the ethernet status (replaces mii-diag) ethtool -s eth0 speed 100 duplex full Force 100Mbit Full duplex ethtool -s eth0 autoneg off Disable auto negotiation ethtool -p eth1 Blink the ethernet led - very useful when supported ip link show Display all interfaces on Linux (similar to ifconfig) ip link set eth0 up Bring device up (or down). Same as "ifconfig eth0 up" ip addr show Display all IP addresses on Linux (similar to ifconfig) ip neigh show Similar to arp -a Other OSes ifconfig fxp0 Check the "media" field on FreeBSD arp -a Check the router (or host) ARP entry (all OS) ping cb.vu The first thing to try... traceroute cb.vu Print the route path to destination ifconfig fxp0 media 100baseTX mediaopt full-duplex 100Mbit full duplex (FreeBSD) netstat -s System-wide statistics for each network protocol Additional commands which are not always installed per default but easy to find: arping <IP_ADDRESS> Ping on ethernet layer tcptraceroute -f 5 cb.vu uses tcp instead of icmp to trace through firewalls Routing Print routing table route -n Linux or use "ip route" netstat -rn Linux, BSD and UNIX route print Windows Add and delete a route FreeBSD route add <IP_ADDRESS>/16 <IP_ADDRESS> route delete <IP_ADDRESS>/16 route add default <IP_ADDRESS> Add the route permanently in /etc/rc.conf static_routes="myroute" route_myroute="-net <IP_ADDRESS>/16 <IP_ADDRESS>" Linux route add -net <IP_ADDRESS> netmask <IP_ADDRESS> gw <IP_ADDRESS> ip route add <IP_ADDRESS>/24 via <IP_ADDRESS> same as above with ip route route add -net <IP_ADDRESS> netmask <IP_ADDRESS> dev eth0 route add default gw <IP_ADDRESS> ip route add default via <IP_ADDRESS> dev eth0 same as above with ip route route delete -net <IP_ADDRESS> netmask <IP_ADDRESS> Solaris route add -net <IP_ADDRESS> -netmask <IP_ADDRESS> <IP_ADDRESS> route add default <IP_ADDRESS> 1 1 = hops to the next gateway route change default <IP_ADDRESS> 1 Permanent entries are set in entry in /etc/defaultrouter. Windows Route add <IP_ADDRESS> mask <IP_ADDRESS> <IP_ADDRESS> Route add <IP_ADDRESS> mask <IP_ADDRESS> <IP_ADDRESS> Use add -p to make the route persistent. Configure additional IP addresses Linux ifconfig eth0 <IP_ADDRESS> netmask <IP_ADDRESS> First IP ifconfig eth0:0 <IP_ADDRESS> netmask <IP_ADDRESS> Second IP ip addr add <IP_ADDRESS>/24 dev eth0 Equivalent ip commands ip addr add <IP_ADDRESS>/24 dev eth0 label eth0:1 FreeBSD ifconfig fxp0 inet <IP_ADDRESS>/24 First IP ifconfig fxp0 alias <IP_ADDRESS> netmask <IP_ADDRESS> Second IP ifconfig fxp0 -alias <IP_ADDRESS> Remove second IP alias Permanent entries in /etc/rc.conf ifconfig_fxp0="inet <IP_ADDRESS> netmask <IP_ADDRESS>" ifconfig_fxp0_alias0="<IP_ADDRESS> netmask <IP_ADDRESS>" Solaris Check the settings with ifconfig -a ifconfig hme0 plumb Enable the network card ifconfig hme0 <IP_ADDRESS> netmask <IP_ADDRESS> up First IP ifconfig hme0:1 <IP_ADDRESS> netmask <IP_ADDRESS> up Second IP Change MAC address Normally you have to bring the interface down before the change. Don't tell me why you want to change the MAC address... ifconfig eth0 down ifconfig eth0 hw ether 00:01:02:03:04:05 Linux ifconfig fxp0 link 00:01:02:03:04:05 FreeBSD ifconfig hme0 ether 00:01:02:03:04:05 Solaris sudo ifconfig en0 ether 00:01:02:03:04:05 OS X Tiger, Snow Leopard LAN* sudo ifconfig en0 lladdr 00:01:02:03:04:05 OS X Leopard *Typical wireless interface is en1 and needs do disassociate from any network first (osxdaily howto). echo "alias airport='/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport'"\ >> ~/.bash_profile or symlink to /usr/sbin airport -z Disassociate from wireless networks airport -I Get info from wireless network Many tools exist for Windows. For example etherchange. Or look for "Mac Makeup", "smac". Ports in use Listening open ports: netstat -an | grep LISTEN lsof -i Linux list all Internet connections socklist Linux display list of open sockets sockstat -4 FreeBSD application listing netstat -anp --udp --tcp | grep LISTEN Linux netstat -tup List active connections to/from system (Linux) netstat -tupl List listening ports from system (Linux) netstat -ano Windows Firewall Check if a firewall is running (typical configuration only): Linux iptables -L -n -v For status Open the iptables firewall iptables -P INPUT ACCEPT Open everything iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT iptables -Z Zero the packet and byte counters in all chains iptables -F Flush all chains iptables -X Delete all chains FreeBSD ipfw show For status ipfw list 65535 if answer is "65535 deny ip from any to any" the fw is disabled sysctl net.inet.ip.fw.enable=0 Disable sysctl net.inet.ip.fw.enable=1 Enable IP Forward for routing Linux Check and then enable IP forward with: cat /proc/sys/net/ipv4/ip_forward Check IP forward 0=off, 1=on echo 1 > /proc/sys/net/ipv4/ip_forward or edit /etc/sysctl.conf with: net.ipv4.ip_forward = 1 FreeBSD Check and enable with: sysctl net.inet.ip.forwarding Check IP forward 0=off, 1=on sysctl net.inet.ip.forwarding=1 sysctl net.inet.ip.fastforwarding=1 For dedicated router or firewall Permanent with entry in /etc/rc.conf: gateway_enable="YES" Set to YES if this host will be a gateway. Solaris ndd -set /dev/ip ip_forwarding 1 Set IP forward 0=off, 1=on NAT Network Address Translation Linux iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE to activate NAT iptables -t nat -A PREROUTING -p tcp -d <IP_ADDRESS> --dport 20022 -j DNAT \ --to <IP_ADDRESS>:22 Port forward 20022 to internal IP port ssh iptables -t nat -A PREROUTING -p tcp -d <IP_ADDRESS> --dport 993:995 -j DNAT \ --to <IP_ADDRESS>:993-995 Port forward of range 993-995 ip route flush cache iptables -L -t nat Check NAT status Delete the port forward with -D instead of -A. The program netstat-nat is very useful to track connections (it uses /proc/net/ip_conntrack or /proc/net/nf_conntrack). netstat-nat -n show all connections with IPs FreeBSD natd -s -m -u -dynamic -f /etc/natd.conf -n fxp0 Or edit /etc/rc.conf with: firewall_enable="YES" Set to YES to enable firewall functionality firewall_type="open" Firewall type (see /etc/rc.firewall) natd_enable="YES" Enable natd (if firewall_enable == YES). natd_interface="tun0" Public interface or IP address to use. natd_flags="-s -m -u -dynamic -f /etc/natd.conf" Port forward with: cat /etc/natd.conf same_ports yes use_sockets yes unregistered_only redirect_port tcp insideIP:2300-2399 3300-3399 port range redirect_port udp <IP_ADDRESS>:7777 7777 DNS On Unix the DNS entries are valid for all interfaces and are stored in /etc/resolv.conf. The domain to which the host belongs is also stored in this file. A minimal configuration is: nameserver <IP_ADDRESS> search sleepyowl.net intern.lab domain sleepyowl.net Check the system domain name with: hostname -d Same as dnsdomainname Windows On Windows the DNS are configured per interface. To display the configured DNS and to flush the DNS cache use: ipconfig /? Display help ipconfig /all See all information including DNS Flush DNS Flush the OS DNS cache, some application using their own cache (e.g. Firefox) and will be unaffected. /etc/init.d/nscd restart Restart nscd if used - Linux/BSD/Solaris lookupd -flushcache OS X Tiger dscacheutil -flushcache OS X Leopard and newer ipconfig /flushdns Windows Forward queries Dig is you friend to test the DNS settings. For example the public DNS server <IP_ADDRESS> ns.second-ns.de can be used for testing. See from which server the client receives the answer (simplified answer). dig sleepyowl.net sleepyowl.net. 600 IN A <IP_ADDRESS> ;; SERVER: <IP_ADDRESS>#53(<IP_ADDRESS>) The router <IP_ADDRESS> answered and the response is the A entry. Any entry can be queried and the DNS server can be selected with @: dig MX google.com dig @<IP_ADDRESS> NS sun.com To test the local server dig @<IP_ADDRESS> NS MX heise.de Query an external server dig AXFR @ns1.xname.org cb.vu Get the full zone (zone transfer) The program host is also powerful. host -t MX cb.vu Get the mail MX entry host -t NS -T sun.com Get the NS record over a TCP connection host -a sleepyowl.net Get everything Reverse queries Find the name belonging to an IP address (in-addr.arpa.). This can be done with dig, host and nslookup: dig -x <IP_ADDRESS> host <IP_ADDRESS> nslookup <IP_ADDRESS> /etc/hosts Single hosts can be configured in the file /etc/hosts instead of running named locally to resolve the hostname queries. The format is simple, for example: <IP_ADDRESS> sleepyowl.net sleepyowl The priority between hosts and a dns query, that is the name resolution order, can be configured in /etc/nsswitch.conf AND /etc/host.conf. The file also exists on Windows, it is usually in: C:\WINDOWS\SYSTEM32\DRIVERS\ETC DHCP Linux Some distributions (SuSE) use dhcpcd as client. The default interface is eth0. dhcpcd -n eth0 Trigger a renew (does not always work) dhcpcd -k eth0 release and shutdown The lease with the full information is stored in: /var/lib/dhcpcd/dhcpcd-eth0.info FreeBSD FreeBSD (and Debian) uses dhclient. To configure an interface (for example bge0) run: dhclient bge0 The lease with the full information is stored in: /var/db/dhclient.leases.bge0 Use /etc/dhclient.conf to prepend options or force different options: cat /etc/dhclient.conf interface "rl0" { prepend domain-name-servers <IP_ADDRESS>; default domain-name "sleepyowl.net"; supersede domain-name "sleepyowl.net"; } Windows The dhcp lease can be renewed with ipconfig: ipconfig /renew renew all adapters ipconfig /renew LAN renew the adapter named "LAN" ipconfig /release WLAN release the adapter named "WLAN" Yes it is a good idea to rename you adapter with simple names! Traffic analysis Bmon is a small console bandwidth monitor and can display the flow on different interfaces. Sniff with tcpdump tcpdump -nl -i bge0 not port ssh and src \(<IP_ADDRESS> or <IP_ADDRESS>\) tcpdump -n -i eth1 net <IP_ADDRESS> select to/from a single IP tcpdump -n -i eth1 net <IP_ADDRESS>/24 select traffic to/from a network tcpdump -l > dump && tail -f dump Buffered output tcpdump -i rl0 -w traffic.rl0 Write traffic headers in binary file tcpdump -i rl0 -s 0 -w traffic.rl0 Write traffic + payload in binary file tcpdump -r traffic.rl0 Read from file (also for ethereal tcpdump port 80 The two classic commands tcpdump host google.com tcpdump -i eth0 -X port \(110 or 143\) Check if pop or imap is secure tcpdump -n -i eth0 icmp Only catch pings tcpdump -i eth0 -s 0 -A port 80 | grep GET -s 0 for full packet -A for ASCII Additional important options: -A Print each packets in clear text (without header) -X Print packets in hex and ASCII -l Make stdout line buffered -D Print all interfaces available On Windows use windump from www.winpcap.org. Use windump -D to list the interfaces. Scan with nmap Nmap is a port scanner with OS detection, it is usually installed on most distributions and is also available for Windows. If you don't scan your servers, hackers do it for you... nmap cb.vu scans all reserved TCP ports on the host nmap -sP <IP_ADDRESS>/24 Find out which IP are used and by which host on 0/24 nmap -sS -sV -O cb.vu Do a stealth SYN scan with version and OS detection PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 3.8.1p1 FreeBSD-20060930 (protocol 2.0) 25/tcp open smtp Sendmail smtpd 8.13.6/8.13.6 80/tcp open http Apache httpd 2.0.59 ((FreeBSD) DAV/2 PHP/4. [...] Running: FreeBSD 5.X Uptime 33.120 days (since Fri Aug 31 11:41:04 2007) Other non standard but useful tools are hping (www.hping.org) an IP packet assembler/analyzer and fping (fping.sourceforge.net). fping can check multiple hosts in a round-robin fashion. Traffic control (QoS) Traffic control manages the queuing, policing, scheduling, and other traffic parameters for a network. The following examples are simple practical uses of the Linux and FreeBSD capabilities to better use the available bandwidth. Limit upload DSL or cable modems have a long queue to improve the upload throughput. However filling the queue with a fast device (e.g. ethernet) will dramatically decrease the interactivity. It is therefore useful to limit the device upload rate to match the physical capacity of the modem, this should greatly improve the interactivity. Set to about 90% of the modem maximal (cable) speed. Linux For a 512 Kbit upload modem. tc qdisc add dev eth0 root tbf rate 480kbit latency 50ms burst 1540 tc -s qdisc ls dev eth0 Status tc qdisc del dev eth0 root Delete the queue tc qdisc change dev eth0 root tbf rate 220kbit latency 50ms burst 1540 FreeBSD FreeBSD uses the dummynet traffic shaper which is configured with ipfw. Pipes are used to set limits the bandwidth in units of [K|M]{bit/s|Byte/s}, 0 means unlimited bandwidth. Using the same pipe number will reconfigure it. For example limit the upload bandwidth to 500 Kbit. kldload dummynet load the module if necessary ipfw pipe 1 config bw 500Kbit/s create a pipe with limited bandwidth ipfw add pipe 1 ip from me to any divert the full upload into the pipe Quality of service Linux Priority queuing with tc to optimize VoIP. See the full example on voip-info.org or www.howtoforge.com. Suppose VoIP uses udp on ports 10000:11024 and device eth0 (could also be ppp0 or so). The following commands define the QoS to three queues and force the VoIP traffic to queue 1 with QoS 0x1e (all bits set). The default traffic flows into queue 3 and QoS Minimize-Delay flows into queue 2. tc qdisc add dev eth0 root handle 1: prio priomap 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 0 tc qdisc add dev eth0 parent 1:1 handle 10: sfq tc qdisc add dev eth0 parent 1:2 handle 20: sfq tc qdisc add dev eth0 parent 1:3 handle 30: sfq tc filter add dev eth0 protocol ip parent 1: prio 1 u32 \ match ip dport 10000 0x3C00 flowid 1:1 use server port range match ip dst <IP_ADDRESS> flowid 1:1 or/and use server IP Status and remove with tc -s qdisc ls dev eth0 queue status tc qdisc del dev eth0 root delete all QoS Calculate port range and mask The tc filter defines the port range with port and mask which you have to calculate. Find the 2^N ending of the port range, deduce the range and convert to HEX. This is your mask. Example for 10000 -> 11024, the range is 1024. 2^13 (8192) < 10000 < 2^14 (16384) ending is 2^14 = 16384 echo "obase=16;(2^14)-1024" | bc mask is 0x3C00 FreeBSD The max link bandwidth is 500Kbit/s and we define 3 queues with priority 100:10:1 for VoIP:ssh:all the rest. ipfw pipe 1 config bw 500Kbit/s ipfw queue 1 config pipe 1 weight 100 ipfw queue 2 config pipe 1 weight 10 ipfw queue 3 config pipe 1 weight 1 ipfw add 10 queue 1 proto udp dst-port 10000-11024 ipfw add 11 queue 1 proto udp dst-ip <IP_ADDRESS> or/and use server IP ipfw add 20 queue 2 dsp-port ssh ipfw add 30 queue 3 from me to any all the rest Status and remove with ipfw list rules status ipfw pipe list pipe status ipfw flush deletes all rules but default NIS Debugging Some commands which should work on a well configured NIS client: ypwhich get the connected NIS server name domainname The NIS domain name as configured ypcat group should display the group from the NIS server cd /var/yp && make Rebuild the yp database rpcinfo -p servername Report RPC services of the server Is ypbind running? ps auxww | grep ypbind /usr/sbin/ypbind -s -m -S servername1,servername2 FreeBSD /usr/sbin/ypbind Linux yppoll passwd.byname Map passwd.byname has order number<PHONE_NUMBER>. Mon Sep 24 13:57:21 2007 The master server is servername.domain.net. Linux cat /etc/yp.conf ypserver servername domain domain.net broadcast Netcat Netcat (nc) is better known as the "network Swiss Army Knife", it can manipulate, create or read/write TCP/IP connections. Here some useful examples, there are many more on the net, for example g-loaded.eu[...] and here. You might need to use the command netcat instead of nc. Also see the similar command socat. File transfer Copy a large folder over a raw tcp connection. The transfer is very quick (no protocol overhead) and you don't need to mess up with NFS or SMB or FTP or so, simply make the file available on the server, and get it from the client. Here <IP_ADDRESS> is the server IP address. servertar -cf - -C VIDEO_TS . | nc -l -p 4444 Serve tar folder on port 4444 clientnc <IP_ADDRESS> 4444 | tar xpf - -C VIDEO_TS Pull the file on port 4444 servercat largefile | nc -l 5678 Server a single file clientnc <IP_ADDRESS> 5678 > largefile Pull the single file serverdd if=/dev/da0 | nc -l 4444 Server partition image clientnc <IP_ADDRESS> 4444 | dd of=/dev/da0 Pull partition to clone clientnc <IP_ADDRESS> 4444 | dd of=da0.img Pull partition to file Other hacks Specially here, you must know what you are doing. Remote shell Option -e only on the Windows version? Or use nc 1.10. nc -lp 4444 -e /bin/bash Provide a remote shell (server backdoor) nc -lp 4444 -e cmd.exe remote shell for Windows Emergency web server Serve a single file on port 80 in a loop. while true; do nc -l -p 80 < unixtoolbox.xhtml; done Chat Alice and Bob can chat over a simple TCP socket. The text is transferred with the enter key. alicenc -lp 4444 bob nc <IP_ADDRESS> 4444 SSH SCP Public key | Fingerprint | SCP | Tunneling See other tricks 25 ssh cmd Public key authentication Connect to a host without password using public key authentication. The idea is to append your public key to the authorized_keys2 file on the remote host. For this example let's connect host-client to host-server, the key is generated on the client. With cygwin you might have to create your home directoy and the .ssh directory with mkdir -p /home/USER/.ssh Use ssh-keygen to generate a key pair. ~/.ssh/id_dsa is the private key, ~/.ssh/id_dsa.pub is the public key. Copy only the public key to the server and append it to the file ~/.ssh/authorized_keys2 on your home on the server. ssh-keygen -t dsa -N '' cat ~/.ssh/id_dsa.pub | ssh you@host-server "cat - >> ~/.ssh/authorized_keys2" Using the Windows client from ssh.com The non commercial version of the ssh.com client can be downloaded the main ftp site: ftp.ssh.com/pub/ssh/. Keys generated by the ssh.com client need to be converted for the OpenSSH server. This can be done with the ssh-keygen command. Create a key pair with the ssh.com client: Settings - User Authentication - Generate New.... I use Key type DSA; key length 2048. Copy the public key generated by the ssh.com client to the server into the ~/.ssh folder. The keys are in C:\Documents and Settings\%USERNAME%\Application Data\SSH\UserKeys. Use the ssh-keygen command on the server to convert the key: cd ~/.ssh ssh-keygen -i -f keyfilename.pub >> authorized_keys2 Notice: We used a DSA key, RSA is also possible. The key is not protected by a password. Using putty for Windows Putty is a simple and free ssh client for Windows. Create a key pair with the puTTYgen program. Save the public and private keys (for example into C:\Documents and Settings\%USERNAME%\.ssh). Copy the public key to the server into the ~/.ssh folder: scp .ssh/puttykey.pub root@<IP_ADDRESS>:.ssh/ Use the ssh-keygen command on the server to convert the key for OpenSSH: cd ~/.ssh ssh-keygen -i -f puttykey.pub >> authorized_keys2 Point the private key location in the putty settings: Connection - SSH - Auth Check fingerprint At the first login, ssh will ask if the unknown host with the fingerprint has to be stored in the known hosts. To avoid a man-in-the-middle attack the administrator of the server can send you the server fingerprint which is then compared on the first login. Use ssh-keygen -l to get the fingerprint (on the server): ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key.pub For RSA key 2048 61:33:be:9b:ae:6c:36:31:fd:83:98:b7:99:2d:9f:cd /etc/ssh/ssh_host_rsa_key.pub ssh-keygen -l -f /etc/ssh/ssh_host_dsa_key.pub For DSA key (default) 2048 14:4a:aa:d9:73:25:46:6d:0a:48:35:c7:f4:16:d4:ee /etc/ssh/ssh_host_dsa_key.pub Now the client connecting to this server can verify that he is connecting to the right server: ssh linda The authenticity of host 'linda (<IP_ADDRESS>)' can't be established. DSA key fingerprint is 14:4a:aa:d9:73:25:46:6d:0a:48:35:c7:f4:16:d4:ee. Are you sure you want to continue connecting (yes/no)? yes Secure file transfer Some simple commands: scp file.txt host-two:/tmp scp joe@host-two:/www/*.html /www/tmp scp -r joe@host-two:/www /www/tmp In Konqueror or Midnight Commander it is possible to access a remote file system with the address fish://user@gate. However the implementation is very slow. Furthermore it is possible to mount a remote folder with sshfs a file system client based on SCP. See fuse sshfs. ssh_exchange_identification: Connection closed by remote host With this error try the following on the server: echo 'SSHD: ALL' >> /etc/hosts.allow /etc/init.d/sshd restart Tunneling SSH tunneling allows to forward or reverse forward a port over the SSH connection, thus securing the traffic and accessing ports which would otherwise be blocked. This only works with TCP. The general nomenclature for forward and reverse is (see also ssh and NAT example): ssh -L localport:desthost:destport user@gate desthost as seen from the gate ssh -R destport:desthost:localport user@gate forwards your localport to destination desthost:localport as seen from the client initiating the tunnel ssh -X user@gate To force X forwarding This will connect to gate and forward the local port to the host desthost:destport. Note desthost is the destination host as seen by the gate, so if the connection is to the gate, then desthost is localhost. More than one port forward is possible. Direct forward on the gate Let say we want to access the CVS (port 2401) and http (port 80) which are running on the gate. This is the simplest example, desthost is thus localhost, and we use the port 8080 locally instead of 80 so we don't need to be root. Once the ssh session is open, both services are accessible on the local ports. ssh -L 2401:localhost:2401 -L 8080:localhost:80 user@gate Netbios and remote desktop forward to a second server Let say a Windows smb server is behind the gate and is not running ssh. We need access to the smb share and also remote desktop to the server. ssh -L 139:smbserver:139 -L 3388:smbserver:3389 user@gate The smb share can now be accessed with \\<IP_ADDRESS>\, but only if the local share is disabled, because the local share is listening on port 139. It is possible to keep the local share enabled, for this we need to create a new virtual device with a new IP address for the tunnel, the smb share will be connected over this address. Furthermore the local RDP is already listening on 3389, so we choose 3388. For this example let's use a virtual IP of <IP_ADDRESS>. With putty use Source port=<IP_ADDRESS>:139. It is possible to create multiple loop devices and tunnel. On Windows 2000, only putty worked for me. On Windows Vista also forward the port 445 in addition to the port 139. Also on Vista the patch KB942624 prevents the port 445 to be forwarded, so I had to uninstall this path in Vista. With the ssh.com client, disable "Allow local connections only". Since ssh.com will bind to all addresses, only a single share can be connected. Now create the loopback interface with IP <IP_ADDRESS>: System->Control Panel->Add Hardware Yes, Hardware is already connected Add a new hardware device (at bottom). Install the hardware that I manually select Network adapters Microsoft , Microsoft Loopback Adapter. Configure the IP address of the fake device to <IP_ADDRESS> mask <IP_ADDRESS>, no gateway. advanced->WINS, Enable LMHosts Lookup; Disable NetBIOS over TCP/IP. Enable Client for Microsoft Networks. Disable File and Printer Sharing for Microsoft Networks. I HAD to reboot for this to work. Now connect to the smb share with \\<IP_ADDRESS> and remote desktop to <IP_ADDRESS>:3388. Debug If it is not working: Are the ports forwarded: netstat -an? Look at <IP_ADDRESS>:139 or <IP_ADDRESS>:139 Does telnet <IP_ADDRESS> 139 connect? You need the checkbox "Local ports accept connections from other hosts". Is "File and Printer Sharing for Microsoft Networks" disabled on the loopback interface? Connect two clients behind NAT Suppose two clients are behind a NAT gateway and client cliadmin has to connect to client cliuser (the destination), both can login to the gate with ssh and are running Linux with sshd. You don't need root access anywhere as long as the ports on gate are above 1024. We use 2022 on gate. Also since the gate is used locally, the option GatewayPorts is not necessary. On client cliuser (from destination to gate): ssh -R 2022:localhost:22 user@gate forwards client 22 to gate:2022 On client cliadmin (from host to gate): ssh -L 3022:localhost:2022 admin@gate forwards client 3022 to gate:2022 Now the admin can connect directly to the client cliuser with: ssh -p 3022 admin@localhost local:3022 -> gate:2022 -> client:22 Connect to VNC behind NAT Suppose a Windows client with VNC listening on port 5900 has to be accessed from behind NAT. On client cliwin to gate: ssh -R 15900:localhost:5900 user@gate On client cliadmin (from host to gate): ssh -L 5900:localhost:15900 admin@gate Now the admin can connect directly to the client VNC with: vncconnect -display :0 localhost Dig a multi-hop ssh tunnel Suppose you can not reach a server directly with ssh, but only via multiple intermediate hosts (for example because of routing issues). Sometimes it is still necessary to get a direct client - server connection, for example to copy files with scp, or forward other ports like smb or vnc. One way to do this is to chain tunnels together to forward a port to the server along the hops. This "carrier" port only reaches its final destination on the last connection to the server. Suppose we want to forward the ssh port from a client to a server over two hops. Once the tunnel is build, it is possible to connect to the server directly from the client (and also add an other port forward). Create tunnel in one shell client -> host1 -> host2 -> server and dig tunnel 5678 client>ssh -L5678:localhost:5678 host1 5678 is an arbitrary port for the tunnel host_1>ssh -L5678:localhost:5678 host2 chain 5678 from host1 to host2 host_2>ssh -L5678:localhost:22 server end the tunnel on port 22 on the server Use tunnel with an other shell client -> server using tunnel 5678 ssh -p 5678 localhost connect directly from client to server scp -P 5678 myfile localhost:/tmp/ or copy a file directly using the tunnel rsync -e 'ssh -p 5678' myfile localhost:/tmp/ or rsync a file directly to the server Autoconnect and keep alive script I use variations of the following script to keep a machine reacheable over a reverse ssh tunnel. The connection is automatically rebuilt if closed. You can add multiple -L or -R tunnels on one line. #!/bin/sh COMMAND="ssh -N -f -g -R 3022:localhost:22<EMAIL_ADDRESS>pgrep -f -x "$COMMAND" > /dev/null 2>&1 || $COMMAND exit 0 1 * * * * colin /home/colin/port_forward.sh crontab entry (here hourly) VPN with SSH As of version 4.3, OpenSSH can use the tun/tap device to encrypt a tunnel. This is very similar to other TLS based VPN solutions like OpenVPN. One advantage with SSH is that there is no need to install and configure additional software. Additionally the tunnel uses the SSH authentication like pre shared keys. The drawback is that the encapsulation is done over TCP which might result in poor performance on a slow link. Also the tunnel is relying on a single (fragile) TCP connection. This technique is very useful for a quick IP based VPN setup. There is no limitation as with the single TCP port forward, all layer 3/4 protocols like ICMP, TCP/UDP, etc. are forwarded over the VPN. In any case, the following options are needed in the sshd_conf file: PermitRootLogin yes PermitTunnel yes Single P2P connection Here we are connecting two hosts, hclient and hserver with a peer to peer tunnel. The connection is started from hclient to hserver and is done as root. The tunnel end points are <IP_ADDRESS> (server) and <IP_ADDRESS> (client) and we create a device tun5 (this could also be an other number). The procedure is very simple: Connect with SSH using the tunnel option -w Configure the IP addresses of the tunnel. Once on the server and once on the client. Connect to the server Connection started on the client and commands are executed on the server. Server is on Linux cli>ssh -w5:5 root@hserver srv>ifconfig tun5 <IP_ADDRESS> netmask <IP_ADDRESS> Executed on the server shell Server is on FreeBSD cli>ssh -w5:5 root@hserver srv>ifconfig tun5 <IP_ADDRESS> <IP_ADDRESS> Executed on the server shell Configure the client Commands executed on the client: cli>ifconfig tun5 <IP_ADDRESS> netmask <IP_ADDRESS> Client is on Linux cli>ifconfig tun5 <IP_ADDRESS> <IP_ADDRESS> Client is on FreeBSD The two hosts are now connected and can transparently communicate with any layer 3/4 protocol using the tunnel IP addresses. Connect two networks In addition to the p2p setup above, it is more useful to connect two private networks with an SSH VPN using two gates. Suppose for the example, netA is <IP_ADDRESS>/24 and netB <IP_ADDRESS>/24. The procedure is similar as above, we only need to add the routing. NAT must be activated on the private interface only if the gates are not the same as the default gateway of their network. <IP_ADDRESS>/24 (netA)|gateA <-> gateB|<IP_ADDRESS>/24 (netB) Connect with SSH using the tunnel option -w. Configure the IP addresses of the tunnel. Once on the server and once on the client. Add the routing for the two networks. If necessary, activate NAT on the private interface of the gate. The setup is started from gateA in netA. Connect from gateA to gateB Connection is started from gateA and commands are executed on gateB. gateB is on Linux gateA>ssh -w5:5 root@gateB gateB>ifconfig tun5 <IP_ADDRESS> netmask <IP_ADDRESS> Executed on the gateB shell gateB>route add -net <IP_ADDRESS> netmask <IP_ADDRESS> dev tun5 gateB>echo 1 > /proc/sys/net/ipv4/ip_forward Only needed if not default gw gateB>iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE gateB is on FreeBSD gateA>ssh -w5:5 root@gateB Creates the tun5 devices gateB>ifconfig tun5 <IP_ADDRESS> <IP_ADDRESS> Executed on the gateB shell gateB>route add <IP_ADDRESS>/24 <IP_ADDRESS> gateB>sysctl net.inet.ip.forwarding=1 Only needed if not default gw gateB>natd -s -m -u -dynamic -n fxp0 see NAT gateA>sysctl net.inet.ip.fw.enable=1 Configure gateA Commands executed on gateA: gateA is on Linux gateA>ifconfig tun5 <IP_ADDRESS> netmask <IP_ADDRESS> gateA>route add -net <IP_ADDRESS> netmask <IP_ADDRESS> dev tun5 gateA>echo 1 > /proc/sys/net/ipv4/ip_forward gateA>iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE gateA is on FreeBSD gateA>ifconfig tun5 <IP_ADDRESS> <IP_ADDRESS> gateA>route add <IP_ADDRESS>/24 <IP_ADDRESS> gateA>sysctl net.inet.ip.forwarding=1 gateA>natd -s -m -u -dynamic -n fxp0 see NAT gateA>sysctl net.inet.ip.fw.enable=1 The two private networks are now transparently connected via the SSH VPN. The IP forward and NAT settings are only necessary if the gates are not the default gateways. In this case the clients would not know where to forward the response, and nat must be activated. RSYNC Rsync can almost completely replace cp and scp, furthermore interrupted transfers are efficiently restarted. A trailing slash (and the absence thereof) has different meanings, the man page is good... Here some examples: Copy the directories with full content: rsync -a /home/colin/ /backup/colin/ "archive" mode. e.g keep the same rsync -a /var/ /var_bak/ rsync -aR --delete-during /home/user/ /backup/ use relative (see below) Same as before but over the network and with compression. Rsync uses SSH for the transport per default and will use the ssh key if they are set. Use ":" as with SCP. A typical remote copy: rsync -axSRzv /home/user/ user@server:/backup/user/ Copy to remote rsync -a 'user@server:My\ Documents' My\ Documents Quote AND escape spaces for the remote shell Exclude any directory tmp within /home/user/ and keep the relative folders hierarchy, that is the remote directory will have the structure /backup/home/user/. This is typically used for backups. rsync -azR --exclude=tmp/ /home/user/ user@server:/backup/ Use port 20022 for the ssh connection: rsync -az -e 'ssh -p 20022' /home/colin/ user@server:/backup/colin/ Using the rsync daemon (used with "::") is much faster, but not encrypted over ssh. The location of /backup is defined by the configuration in /etc/rsyncd.conf. The variable RSYNC_PASSWORD can be set to avoid the need to enter the password manually. rsync -axSRz /home/ ruser@hostname::rmodule/backup/ rsync -axSRz ruser@hostname::rmodule/backup/ /home/ To copy back Some important options: -a, --archive archive mode; same as -rlptgoD (no -H) -r, --recursive recurse into directories -R, --relative use relative path names -H, --hard-links preserve hard links -S, --sparse handle sparse files efficiently -x, --one-file-system don't cross file system boundaries --exclude=PATTERN exclude files matching PATTERN --delete-during receiver deletes during xfer, not before --delete-after receiver deletes after transfer, not before Rsync on Windows Rsync is available for Windows through cygwin or as stand-alone packaged in cwrsync. This is very convenient for automated backups. Install one of them (not both) and add the path to the Windows system variables: Control Panel -> System -> tab Advanced, button Environment Variables. Edit the "Path" system variable and add the full path to the installed rsync, e.g. C:\Program Files\cwRsync\bin or C:\cygwin\bin. This way the commands rsync and ssh are available in a Windows command shell. Public key authentication Rsync is automatically tunneled over SSH and thus uses the SSH authentication on the server. Automatic backups have to avoid a user interaction, for this the SSH public key authentication can be used and the rsync command will run without a password. All the following commands are executed within a Windows console. In a console (Start -> Run -> cmd) create and upload the key as described in SSH, change "user" and "server" as appropriate. If the file authorized_keys2 does not exist yet, simply copy id_dsa.pub to authorized_keys2 and upload it. ssh-keygen -t dsa -N '' Creates a public and a private key rsync user@server:.ssh/authorized_keys2 . Copy the file locally from the server cat id_dsa.pub >> authorized_keys2 Or use an editor to add the key rsync authorized_keys2 user@server:.ssh/ Copy the file back to the server del authorized_keys2 Remove the local copy Now test it with (in one line): rsync -rv "/cygdrive/c/Documents and Settings/%USERNAME%/My Documents/" \ 'user@server:My\ Documents/' Automatic backup Use a batch file to automate the backup and add the file in the scheduled tasks (Programs -> Accessories -> System Tools -> Scheduled Tasks). For example create the file backup.bat and replace user@server. @ECHO OFF REM rsync the directory My Documents SETLOCAL SET CWRSYNCHOME=C:\PROGRAM FILES\CWRSYNC SET CYGWIN=nontsec SET CWOLDPATH=%PATH% REM uncomment the next line when using cygwin SET PATH=%CWRSYNCHOME%\BIN;%PATH% echo Press Control-C to abort rsync -av "/cygdrive/c/Documents and Settings/%USERNAME%/My Documents/" \ 'user@server:My\ Documents/' pause SUDO Sudo is a standard way to give users some administrative rights without giving out the root password. Sudo is very useful in a multi user environment with a mix of server and workstations. Simply call the command with sudo: sudo /etc/init.d/dhcpd restart Run the rc script as root sudo -u sysadmin whoami Run cmd as an other user Configuration Sudo is configured in /etc/sudoers and must only be edited with visudo. The basic syntax is (the lists are comma separated): user hosts = (runas) commands In /etc/sudoers users one or more users or %group (like %wheel) to gain the rights hosts list of hosts (or ALL) runas list of users (or ALL) that the command rule can be run as. It is enclosed in ( )! commands list of commands (or ALL) that will be run as root or as (runas) Additionally those keywords can be defined as alias, they are called User_Alias, Host_Alias, Runas_Alias and Cmnd_Alias. This is useful for larger setups. Here a sudoers example: cat /etc/sudoers Host aliases are subnets or hostnames. Host_Alias DMZ = <IP_ADDRESS>/28 Host_Alias DESKTOP = work1, work2 User aliases are a list of users which can have the same rights User_Alias ADMINS = colin, luca, admin User_Alias DEVEL = joe, jack, julia Runas_Alias DBA = oracle,pgsql Command aliases define the full path of a list of commands Cmnd_Alias SYSTEM = /sbin/reboot,/usr/bin/kill,/sbin/halt,/sbin/shutdown,/etc/init.d/ Cmnd_Alias PW = /usr/bin/passwd [A-z]*, !/usr/bin/passwd root Not root pwd! Cmnd_Alias DEBUG = /usr/sbin/tcpdump,/usr/bin/wireshark,/usr/bin/nmap The actual rules root,ADMINS ALL = (ALL) NOPASSWD: ALL ADMINS can do anything w/o a password. DEVEL DESKTOP = (ALL) NOPASSWD: ALL Developers have full right on desktops DEVEL DMZ = (ALL) NOPASSWD: DEBUG Developers can debug the DMZ servers. User sysadmin can mess around in the DMZ servers with some commands. sysadmin DMZ = (ALL) NOPASSWD: SYSTEM,PW,DEBUG sysadmin ALL,!DMZ = (ALL) NOPASSWD: ALL Can do anything outside the DMZ. %dba ALL = (DBA) ALL Group dba can run as database user. anyone can mount/unmount a cd-rom on the desktop machines ALL DESKTOP = NOPASSWD: /sbin/mount /cdrom,/sbin/umount /cdrom Encrypt Files OpenSSL A single file Encrypt and decrypt: openssl aes-128-cbc -salt -in file -out file.aes openssl aes-128-cbc -d -salt -in file.aes -out file Note that the file can of course be a tar archive. tar and encrypt a whole directory tar -cf - directory | openssl aes-128-cbc -salt -out directory.tar.aes Encrypt openssl aes-128-cbc -d -salt -in directory.tar.aes | tar -x -f - Decrypt tar zip and encrypt a whole directory tar -zcf - directory | openssl aes-128-cbc -salt -out directory.tar.gz.aes Encrypt openssl aes-128-cbc -d -salt -in directory.tar.gz.aes | tar -xz -f - Decrypt Use -k mysecretpassword after aes-128-cbc to avoid the interactive password request. However note that this is highly insecure. Use aes-256-cbc instead of aes-128-cbc to get even stronger encryption. This uses also more CPU. GPG GnuPG is well known to encrypt and sign emails or any data. Furthermore gpg and also provides an advanced key management system. This section only covers files encryption, not email usage, signing or the Web-Of-Trust. The simplest encryption is with a symmetric cipher. In this case the file is encrypted with a password and anyone who knows the password can decrypt it, thus the keys are not needed. Gpg adds an extention ".gpg" to the encrypted file names. gpg -c file Encrypt file with password gpg file.gpg Decrypt file (optionally -o otherfile) Using keys For more details see GPG Quick Start and GPG/PGP Basics and the gnupg documentation among others. The private and public keys are the heart of asymmetric cryptography. What is important to remember: Your public key is used by others to encrypt files that only you as the receiver can decrypt (not even the one who encrypted the file can decrypt it). The public key is thus meant to be distributed. Your private key is encrypted with your passphrase and is used to decrypt files which were encrypted with your public key. The private key must be kept secure. Also if the key or passphrase is lost, so are all the files encrypted with your public key. The key files are called keyrings as they can contain more than one key. First generate a key pair. The defaults are fine, however you will have to enter at least your full name and email and optionally a comment. The comment is useful to create more than one key with the same name and email. Also you should use a "passphrase", not a simple password. gpg --gen-key This can take a long time The keys are stored in ~/.gnupg/ on Unix, on Windows they are typically stored in C:/Documents and Settings/%USERNAME%/Application Data/gnupg/. ~/.gnupg/pubring.gpg Contains your public keys and all others imported ~/.gnupg/secring.gpg Can contain more than one private key Short reminder on most used options: -e encrypt data -d decrypt data -r NAME encrypt for recipient NAME (or 'Full Name' or 'email@domain') -a create ascii armored output of a key -o use as output file The examples use 'Your Name' and 'Alice' as the keys are referred to by the email or full name or partial name. For example I can use 'Colin' or<EMAIL_ADDRESS>for my key [Colin Barschel (cb.vu)]. Encrypt for personal use only No need to export/import any key for this. You have both already. gpg -e -r 'Your Name' file Encrypt with your public key gpg -o file -d file.gpg Decrypt. Use -o or it goes to stdout Encrypt - Decrypt with keys First you need to export your public key for someone else to use it. And you need to import the public say from Alice to encrypt a file for her. You can either handle the keys in simple ascii files or use a public key server. For example Alice export her public key and you import it, you can then encrypt a file for her. That is only Alice will be able to decrypt it. gpg -a -o alicekey.asc --export 'Alice' Alice exported her key in ascii file. gpg --send-keys --keyserver subkeys.pgp.net KEYID Alice put her key on a server. gpg --import alicekey.asc You import her key into your pubring. gpg --search-keys --keyserver subkeys.pgp.net 'Alice' or get her key from a server. Once the keys are imported it is very easy to encrypt or decrypt a file: gpg -e -r 'Alice' file Encrypt the file for Alice. gpg -d file.gpg -o file Decrypt a file encrypted by Alice for you. Key administration gpg --list-keys list public keys and see the KEYIDS The KEYID follows the '/' e.g. for: pub 1024D/D12B77CE the KEYID is D12B77CE gpg --gen-revoke 'Your Name' generate revocation certificate gpg --list-secret-keys list private keys gpg --delete-keys NAME delete a public key from local key ring gpg --delete-secret-key NAME delete a secret key from local key ring gpg --fingerprint KEYID Show the fingerprint of the key gpg --edit-key KEYID Edit key (e.g sign or add/del email) Encrypt Partitions Linux with LUKS | Linux dm-crypt only | FreeBSD GELI | FBSD pwd only | OS X image There are (many) other alternative methods to encrypt disks, I only show here the methods I know and use. Keep in mind that the security is only good as long the OS has not been tempered with. An intruder could easily record the password from the keyboard events. Furthermore the data is freely accessible when the partition is attached and will not prevent an intruder to have access to it in this state. Linux Those instructions use the Linux dm-crypt (device-mapper) facility available on the 2.6 kernel. In this example, lets encrypt the partition /dev/sdc1, it could be however any other partition or disk, or USB or a file based partition created with losetup. In this case we would use /dev/loop0. See file image partition. The device mapper uses labels to identify a partition. We use sdc1 in this example, but it could be any string. dm-crypt with LUKS LUKS with dm-crypt has better encryption and makes it possible to have multiple passphrase for the same partition or to change the password easily. To test if LUKS is available, simply type cryptsetup --help, if nothing about LUKS shows up, use the instructions below Without LUKS. First create a partition if necessary: fdisk /dev/sdc. Create encrypted partition dd if=/dev/urandom of=/dev/sdc1 Optional. For paranoids only (takes days) cryptsetup -y luksFormat /dev/sdc1 This destroys any data on sdc1 cryptsetup luksOpen /dev/sdc1 sdc1 mkfs.ext3 /dev/mapper/sdc1 create ext3 file system mount -t ext3 /dev/mapper/sdc1 /mnt umount /mnt cryptsetup luksClose sdc1 Detach the encrypted partition Attach cryptsetup luksOpen /dev/sdc1 sdc1 mount -t ext3 /dev/mapper/sdc1 /mnt Detach umount /mnt cryptsetup luksClose sdc1 dm-crypt without LUKS cryptsetup -y create sdc1 /dev/sdc1 or any other partition like /dev/loop0 dmsetup ls check it, will display: sdc1 (254, 0) mkfs.ext3 /dev/mapper/sdc1 This is done only the first time! mount -t ext3 /dev/mapper/sdc1 /mnt umount /mnt/ cryptsetup remove sdc1 Detach the encrypted partition Do exactly the same (without the mkfs part!) to re-attach the partition. If the password is not correct, the mount command will fail. In this case simply remove the map sdc1 (cryptsetup remove sdc1) and create it again. FreeBSD The two popular FreeBSD disk encryption modules are gbde and geli. I now use geli because it is faster and also uses the crypto device for hardware acceleration. See The FreeBSD handbook Chapter 18.6 for all the details. The geli module must be loaded or compiled into the kernel: options GEOM_ELI device crypto or as module: echo 'geom_eli_load="YES"' >> /boot/loader.conf or do: kldload geom_eli Use password and key I use those settings for a typical disk encryption, it uses a passphrase AND a key to encrypt the master key. That is you need both the password and the generated key /root/ad1.key to attach the partition. The master key is stored inside the partition and is not visible. See below for typical USB or file based image. Create encrypted partition dd if=/dev/random of=/root/ad1.key bs=64 count=1 this key encrypts the mater key geli init -s 4096 -K /root/ad1.key /dev/ad1 -s 8192 is also OK for disks geli attach -k /root/ad1.key /dev/ad1 DO make a backup of /root/ad1.key dd if=/dev/random of=/dev/ad1.eli bs=1m Optional and takes a long time newfs /dev/ad1.eli Create file system mount /dev/ad1.eli /mnt Attach geli attach -k /root/ad1.key /dev/ad1 fsck -ny -t ffs /dev/ad1.eli In doubt check the file system mount /dev/ad1.eli /mnt Detach The detach procedure is done automatically on shutdown. umount /mnt geli detach /dev/ad1.eli /etc/fstab The encrypted partition can be configured to be mounted with /etc/fstab. The password will be prompted when booting. The following settings are required for this example: grep geli /etc/rc.conf geli_devices="ad1" geli_ad1_flags="-k /root/ad1.key" grep geli /etc/fstab /dev/ad1.eli /home/private ufs rw 0 0 Use password only It is more convenient to encrypt a USB stick or file based image with a passphrase only and no key. In this case it is not necessary to carry the additional key file around. The procedure is very much the same as above, simply without the key file. Let's encrypt a file based image /cryptedfile of 1 GB. dd if=/dev/zero of=/cryptedfile bs=1M count=1000 1 GB file mdconfig -at vnode -f /cryptedfile geli init /dev/md0 encrypts with password only geli attach /dev/md0 newfs -U -m 0 /dev/md0.eli mount /dev/md0.eli /mnt umount /dev/md0.eli geli detach md0.eli It is now possible to mount this image on an other system with the password only. mdconfig -at vnode -f /cryptedfile geli attach /dev/md0 mount /dev/md0.eli /mnt OS X Encrypted Disk Image Don't know by command line only. See OS X Encrypted Disk Image and Apple support SSL Certificates So called SSL/TLS certificates are cryptographic public key certificates and are composed of a public and a private key. The certificates are used to authenticate the endpoints and encrypt the data. They are used for example on a web server (https) or mail server (imaps). Procedure We need a certificate authority to sign our certificate. This step is usually provided by a vendor like Thawte, Verisign, etc., however we can also create our own. Create a certificate signing request. This request is like an unsigned certificate (the public part) and already contains all necessary information. The certificate request is normally sent to the authority vendor for signing. This step also creates the private key on the local machine. Sign the certificate with the certificate authority. If necessary join the certificate and the key in a single file to be used by the application (web server, mail server etc.). Configure OpenSSL We use /usr/local/certs as directory for this example check or edit /etc/ssl/openssl.cnf accordingly to your settings so you know where the files will be created. Here are the relevant part of openssl.cnf: [ CA_default ] dir = /usr/local/certs/CA Where everything is kept certs = $dir/certs Where the issued certs are kept crl_dir = $dir/crl Where the issued crl are kept database = $dir/index.txt database index file. Make sure the directories exist or create them mkdir -p /usr/local/certs/CA cd /usr/local/certs/CA mkdir certs crl newcerts private echo "01" > serial Only if serial does not exist touch index.txt If you intend to get a signed certificate from a vendor, you only need a certificate signing request (CSR). This CSR will then be signed by the vendor for a limited time (e.g. 1 year). Create a certificate authority If you do not have a certificate authority from a vendor, you'll have to create your own. This step is not necessary if one intend to use a vendor to sign the request. To make a certificate authority (CA): openssl req -new -x509 -days 730 -config /etc/ssl/openssl.cnf \ -keyout CA/private/cakey.pem -out CA/cacert.pem Create a certificate signing request To make a new certificate (for mail server or web server for example), first create a request certificate with its private key. If your application do not support encrypted private key (for example UW-IMAP does not), then disable encryption with -nodes. openssl req -new -keyout newkey.pem -out newreq.pem \ -config /etc/ssl/openssl.cnf openssl req -nodes -new -keyout newkey.pem -out newreq.pem \ -config /etc/ssl/openssl.cnf No encryption for the key Keep this created CSR (newreq.pem) as it can be signed again at the next renewal, the signature onlt will limit the validity of the certificate. This process also created the private key newkey.pem. Sign the certificate The certificate request has to be signed by the CA to be valid, this step is usually done by the vendor. Note: replace "servername" with the name of your server in the next commands. cat newreq.pem newkey.pem > new.pem openssl ca -policy policy_anything -out servernamecert.pem \ -config /etc/ssl/openssl.cnf -infiles new.pem mv newkey.pem servernamekey.pem Now servernamekey.pem is the private key and servernamecert.pem is the server certificate. Create united certificate The IMAP server wants to have both private key and server certificate in the same file. And in general, this is also easier to handle, but the file has to be kept securely!. Apache also can deal with it well. Create a file servername.pem containing both the certificate and key. Open the private key (servernamekey.pem) with a text editor and copy the private key into the "servername.pem" file. Do the same with the server certificate (servernamecert.pem). The final servername.pem file should look like this: -----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQDutWy+o/XZ/[...]qK5LqQgT3c9dU6fcR+WuSs6aejdEDDqBRQ -----END RSA PRIVATE KEY----- -----BEGIN CERTIFICATE----- MIIERzCCA7CgAwIBAgIBBDANB[...]iG9w0BAQQFADCBxTELMAkGA1UEBhMCREUx -----END CERTIFICATE----- What we have now in the directory /usr/local/certs/: CA/private/cakey.pem (CA server private key) CA/cacert.pem (CA server public key) certs/servernamekey.pem (server private key) certs/servernamecert.pem (server signed certificate) certs/servername.pem (server certificate with private key) Keep the private key secure! View certificate information To view the certificate information simply do: openssl x509 -text -in servernamecert.pem View the certificate info openssl req -noout -text -in server.csr View the request info openssl s_client -connect cb.vu:443 Check a web server certificate CVS Server setup | CVS test | SSH tunneling | CVS usage Server setup Initiate the CVS Decide where the main repository will rest and create a root cvs. For example /usr/local/cvs (as root): mkdir -p /usr/local/cvs setenv CVSROOT /usr/local/cvs Set CVSROOT to the new location (local) cvs init Creates all internal CVS config files cd /root cvs checkout CVSROOT Checkout the config files to modify them cd CVSROOT edit config ( fine as it is) cvs commit config cat >> writers Create a writers file (optionally also readers) colin ^D Use [Control][D] to quit the edit cvs add writers Add the file writers into the repository cvs edit checkoutlist cat >> checkoutlist writers ^D Use [Control][D] to quit the edit cvs commit Commit all the configuration changes Add a readers file if you want to differentiate read and write permissions Note: Do not (ever) edit files directly into the main cvs, but rather checkout the file, modify it and check it in. We did this with the file writers to define the write access. There are three popular ways to access the CVS at this point. The first two don't need any further configuration. See the examples on CVSROOT below for how to use them: Direct local access to the file system. The user(s) need sufficient file permission to access the CS directly and there is no further authentication in addition to the OS login. However this is only useful if the repository is local. Remote access with ssh with the ext protocol. Any use with an ssh shell account and read/write permissions on the CVS server can access the CVS directly with ext over ssh without any additional tunnel. There is no server process running on the CVS for this to work. The ssh login does the authentication. Remote access with pserver (default port: 2401/tcp). This is the preferred use for larger user base as the users are authenticated by the CVS pserver with a dedicated password database, there is therefore no need for local users accounts. This setup is explained below. Network setup with inetd The CVS can be run locally only if a network access is not needed. For a remote access, the daemon inetd can start the pserver with the following line in /etc/inetd.conf (/etc/xinetd.d/cvs on SuSE): cvspserver stream tcp nowait cvs /usr/bin/cvs cvs \ --allow-root=/usr/local/cvs pserver It is a good idea to block the cvs port from the Internet with the firewall and use an ssh tunnel to access the repository remotely. Separate authentication It is possible to have cvs users which are not part of the OS (no local users). This is actually probably wanted too from the security point of view. Simply add a file named passwd (in the CVSROOT directory) containing the users login and password in the crypt format. This is can be done with the apache htpasswd tool. Note: This passwd file is the only file which has to be edited directly in the CVSROOT directory. Also it won't be checked out. More info with htpasswd --help htpasswd -cb passwd user1 password1 -c creates the file htpasswd -b passwd user2 password2 Now add :cvs at the end of each line to tell the cvs server to change the user to cvs (or whatever your cvs server is running under). It looks like this: cat passwd user1:xsFjhU22u8Fuo:cvs user2:vnefJOsnnvToM:cvs Test it Test the login as normal user (for example here me) cvs -d :pserver:colin@<IP_ADDRESS>:/usr/local/cvs login Logging in to :pserver:colin@<IP_ADDRESS>:2401/usr/local/cvs CVS password: CVSROOT variable This is an environment variable used to specify the location of the repository we're doing operations on. For local use, it can be just set to the directory of the repository. For use over the network, the transport protocol must be specified. Set the CVSROOT variable with setenv CVSROOT string on a csh, tcsh shell, or with export CVSROOT=string on a sh, bash shell. setenv CVSROOT :pserver:username@host:/cvsdirectory For example: setenv CVSROOT /usr/local/cvs Used locally only setenv CVSROOT :local:/usr/local/cvs Same as above setenv CVSROOT :ext:user@cvsserver:/usr/local/cvs Direct access with SSH setenv CVS_RSH ssh for the ext access setenv CVSROOT :pserver:user@cvsserver.254:/usr/local/cvs network with pserver When the login succeeded one can import a new project into the repository: cd into your project root directory cvs import module name vendor tag initial tag cvs -d :pserver:colin@<IP_ADDRESS>:/usr/local/cvs import MyProject MyCompany START Where MyProject is the name of the new project in the repository (used later to checkout). Cvs will import the current directory content into the new project. To checkout: cvs -d :pserver:colin@<IP_ADDRESS>:/usr/local/cvs checkout MyProject or setenv CVSROOT :pserver:colin@<IP_ADDRESS>:/usr/local/cvs cvs checkout MyProject SSH tunneling for CVS We need 2 shells for this. On the first shell we connect to the cvs server with ssh and port-forward the cvs connection. On the second shell we use the cvs normally as if it where running locally. on shell 1: ssh -L2401:localhost:2401 colin@cvs_server Connect directly to the CVS server. Or: ssh -L2401:cvs_server:2401 colin@gateway Use a gateway to reach the CVS on shell 2: setenv CVSROOT :pserver:colin@localhost:/usr/local/cvs cvs login Logging in to :pserver:colin@localhost:2401/usr/local/cvs CVS password: cvs checkout MyProject/src CVS commands and usage Import The import command is used to add a whole directory, it must be run from within the directory to be imported. Say the directory /devel/ contains all files and subdirectories to be imported. The directory name on the CVS (the module) will be called "myapp". cvs import [options] directory-name vendor-tag release-tag cd /devel Must be inside the project to import it cvs import myapp Company R1_0 Release tag can be anything in one word After a while a new directory "/devel/tools/" was added and it has to be imported too. cd /devel/tools cvs import myapp/tools Company R1_0 Checkout update add commit cvs co myapp/tools Will only checkout the directory tools cvs co -r R1_1 myapp Checkout myapp at release R1_1 (is sticky) cvs -q -d update -P A typical CVS update cvs update -A Reset any sticky tag (or date, option) cvs add newfile Add a new file cvs add -kb newfile Add a new binary file cvs commit file1 file2 Commit the two files only cvs commit -m "message" Commit all changes done with a message Create a patch It is best to create and apply a patch from the working development directory related to the project, or from within the source directory. cd /devel/project diff -Naur olddir newdir > patchfile Create a patch from a directory or a file diff -Naur oldfile newfile > patchfile Apply a patch Sometimes it is necessary to strip a directory level from the patch, depending how it was created. In case of difficulties, simply look at the first lines of the patch and try -p0, -p1 or -p2. cd /devel/project patch --dry-run -p0 < patchfile Test the path without applying it patch -p0 < patchfile patch -p1 < patchfile strip off the 1st level from the path SVN Server setup | SVN+SSH | SVN over http | SVN usage Subversion (SVN) is a version control system designed to be the successor of CVS (Concurrent Versions System). The concept is similar to CVS, but many shortcomings where improved. See also the SVN book. Server setup The initiation of the repository is fairly simple (here for example /home/svn/ must exist): svnadmin create --fs-type fsfs /home/svn/project1 Now the access to the repository is made possible with: file:// Direct file system access with the svn client with. This requires local permissions on the file system. svn:// or svn+ssh:// Remote access with the svnserve server (also over SSH). This requires local permissions on the file system (default port: 2690/tcp). http:// Remote access with webdav using apache. No local users are necessary for this method. Using the local file system, it is now possible to import and then check out an existing project. Unlike with CVS it is not necessary to cd into the project directory, simply give the full path: svn import /project1/ file:///home/svn/project1/trunk -m 'Initial import' svn checkout file:///home/svn/project1 The new directory "trunk" is only a convention, this is not required. Remote access with ssh No special setup is required to access the repository via ssh, simply replace file:// with svn+ssh/hostname. For example: svn checkout svn+ssh://hostname/home/svn/project1 As with the local file access, every user needs an ssh access to the server (with a local account) and also read/write access. This method might be suitable for a small group. All users could belong to a subversion group which owns the repository, for example: groupadd subversion groupmod -A user1 subversion chown -R root:subversion /home/svn chmod -R 770 /home/svn Remote access with http (apache) Remote access over http (https) is the only good solution for a larger user group. This method uses the apache authentication, not the local accounts. This is a typical but small apache configuration: LoadModule dav_module modules/mod_dav.so LoadModule dav_svn_module modules/mod_dav_svn.so LoadModule authz_svn_module modules/mod_authz_svn.so Only for access control Location /svn> DAV svn any "/svn/foo" URL will map to a repository /home/svn/foo SVNParentPath /home/svn AuthType Basic AuthName "Subversion repository" AuthzSVNAccessFile /etc/apache2/svn.acl AuthUserFile /etc/apache2/svn-passwd Require valid-user /Location> The apache server needs full access to the repository: chown -R www:www /home/svn Create a user with htpasswd2: htpasswd -c /etc/svn-passwd user1 -c creates the file Access control svn.acl example Default it read access. "* =" would be default no access [/] * = r [groups] project1-developers = joe, jack, jane Give write access to the developers [project1:] @project1-developers = rw SVN commands and usage See also the Subversion Quick Reference Card. Tortoise SVN is a nice Windows interface. Import A new project, that is a directory with some files, is imported into the repository with the import command. Import is also used to add a directory with its content to an existing project. svn help import Get help for any command Add a new directory (with content) into the src dir on project1 svn import /project1/newdir http://host.url/svn/project1/trunk/src -m 'add newdir' Typical SVN commands svn co http://host.url/svn/project1/trunk Checkout the most recent version Tags and branches are created by copying svn mkdir http://host.url/svn/project1/tags/ Create the tags directory svn copy -m "Tag rc1 rel." http://host.url/svn/project1/trunk \ http://host.url/svn/project1/tags/1.0rc1 svn status [--verbose] Check files status into working dir svn add src/file.h src/file.cpp Add two files svn commit -m 'Added new class file' Commit the changes with a message svn ls http://host.url/svn/project1/tags/ List all tags svn move foo.c bar.c Move (rename) files svn delete some_old_file Delete files Useful Commands less | vi | mail | tar | dd | screen | find | Miscellaneous less The less command displays a text document on the console. It is present on most installation. less unixtoolbox.xhtml Some important commands are (^N stands for [control]-[N]): h H good help on display f ^F ^V SPACE Forward one window (or N lines). b ^B ESC-v Backward one window (or N lines). F Forward forever; like "tail -f". /pattern Search forward for (N-th) matching line. ?pattern Search backward for (N-th) matching line. n Repeat previous search (for N-th occurrence). N Repeat previous search in reverse direction. q quit vi Vi is present on ANY Linux/Unix installation (not gentoo?) and it is therefore useful to know some basic commands. There are two modes: command mode and insertion mode. The commands mode is accessed with [ESC], the insertion mode with i. Use : help if you are lost. The editors nano and pico are usually available too and are easier (IMHO) to use. Quit :w newfilename save the file to newfilename :wq or :x save and quit :q! quit without saving Search and move /string Search forward for string ?string Search back for string n Search for next instance of string N Search for previous instance of string { Move a paragraph back } Move a paragraph forward 1G Move to the first line of the file nG Move to the n th line of the file G Move to the last line of the file :%s/OLD/NEW/g Search and replace every occurrence Delete copy paste text dd (dw) Cut current line (word) D Cut to the end of the line x Delete (cut) character yy (yw) Copy line (word) after cursor P Paste after cursor u Undo last modification U Undo all changes to current line mail The mail command is a basic application to read and send email, it is usually installed. To send an email simply type "mail user@domain". The first line is the subject, then the mail content. Terminate and send the email with a single dot (.) in a new line.  Then, after a second or so, nothing continued to happen." . EOT # This is also working with a pipe: echo "This is the mail body" | mail<EMAIL_ADDRESS>This is also a simple way to test the mail server. tar The command tar (tape archive) creates and extracts archives of file and directories. The archive .tar is uncompressed, a compressed archive has the extension .tgz or .tar.gz (zip) or .tbz (bzip2). Do not use absolute path when creating an archive, you probably want to unpack it somewhere else. Some typical commands are: Create cd / tar -cf home.tar home/ archive the whole /home directory (c for create) tar -czf home.tgz home/ same with zip compression tar -cjf home.tbz home/ same with bzip2 compression Only include one (or two) directories from a tree, but keep the relative structure. For example archive /usr/local/etc and /usr/local/www and the first directory in the archive should be local/. tar -C /usr -czf local.tgz local/etc local/www tar -C /usr -xzf local.tgz To untar the local dir into /usr cd /usr; tar -xzf local.tgz Is the same as above Extract tar -tzf home.tgz look inside the archive without extracting (list) tar -xf home.tar extract the archive here (x for extract) tar -xzf home.tgz same with zip compression (-xjf for bzip2 compression) remove leading path gallery2 and extract into gallery tar --strip-components 1 -zxvf gallery2.tgz -C gallery/ tar -xjf home.tbz home/colin/file.txt Restore a single file More advanced tar c dir/ | gzip | ssh user@remote 'dd of=dir.tgz' arch dir/ and store remotely. tar cvf - `find . -print` > backup.tar arch the current directory. tar -cf - -C /etc . | tar xpf - -C /backup/etc Copy directories tar -cf - -C /etc . | ssh user@remote tar xpf - -C /backup/etc Remote copy. tar -czf home.tgz --exclude '*.o' --exclude 'tmp/' home/ dd The program dd (disk dump or destroy disk or see the meaning of dd) is used to copy partitions and disks and for other copy tricks. Typical usage: dd if=source of=target bs=byte size conv=conversion Important conv options: notrunc do not truncate the output file, all zeros will be written as zeros. noerror continue after read errors (e.g. bad blocks) sync pad every input block with Nulls to ibs-size The default byte size is 512 (one block). The MBR, where the partition table is located, is on the first block, the first 63 blocks of a disk are empty. Larger byte sizes are faster to copy but require also more memory. Backup and restore dd if=/dev/hda of=/dev/hdc bs=16065b Copy disk to disk (same size) dd if=/dev/sda7 of=/home/root.img bs=4096 conv=notrunc,noerror Backup / dd if=/home/root.img of=/dev/sda7 bs=4096 conv=notrunc,noerror Restore / dd bs=1M if=/dev/ad4s3e | gzip -c > ad4s3e.gz Zip the backup gunzip -dc ad4s3e.gz | dd of=/dev/ad0s3e bs=1M Restore the zip dd bs=1M if=/dev/ad4s3e | gzip | ssh eedcoba@fry 'dd of=ad4s3e.gz' also remote gunzip -dc ad4s3e.gz | ssh eedcoba@host 'dd of=/dev/ad0s3e bs=1M' dd if=/dev/ad0 of=/dev/ad2 skip=1 seek=1 bs=4k conv=noerror Skip MBR This is necessary if the destination (ad2) is smaller. Recover The command dd will read every single block of the partition. In case of problems it is better to use the option conv=sync,noerror so dd will skip the bad block and write zeros at the destination. Accordingly it is important to set the block size equal or smaller than the disk block size. A 1k size seems safe, set it with bs=1k. If a disk has bad sectors and the data should be recovered from a partition, create an image file with dd, mount the image and copy the content to a new disk. With the option noerror, dd will skip the bad sectors and write zeros instead, thus only the data contained in the bad sectors will be lost. dd if=/dev/hda of=/dev/null bs=1m Check for bad blocks dd bs=1k if=/dev/hda1 conv=sync,noerror,notrunc | gzip | ssh \ Send to remote root@fry 'dd of=hda1.gz bs=1k' dd bs=1k if=/dev/hda1 conv=sync,noerror,notrunc of=hda1.img Store into an image mount -o loop /hda1.img /mnt Mount the image rsync -ax /mnt/ /newdisk/ Copy on a new disk dd if=/dev/hda of=/dev/hda Refresh the magnetic state The above is useful to refresh a disk. It is perfectly safe, but must be unmounted.  The first 446 are for the boot loader, the bytes 446 to 512 are for the partition table. dd if=/dev/sda of=/mbr_sda.bak bs=512 count=1 Backup the full MBR dd if=/dev/zero of=/dev/sda bs=512 count=1 Delete MBR and partition table dd if=/mbr_sda.bak of=/dev/sda bs=512 count=1 Restore the full MBR dd if=/mbr_sda.bak of=/dev/sda bs=446 count=1 Restore only the boot loader dd if=/mbr_sda.bak of=/dev/sda bs=1 count=64 skip=446 seek=446 Restore partition table screen Screen (a must have) has two main functionalities: Run multiple terminal session within a single terminal. A started program is decoupled from the real terminal and can thus run in the background. The real terminal can be closed and reattached later. Short start example start screen with: screen Within the screen session we can start a long lasting program (like top). top Now detach with Ctrl-a Ctrl-d. Reattach the terminal with: screen -R -D In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first. If it was not running create it and notify the user. Or: screen -x Attach to a running screen in a multi display mode. The console is thus shared among multiple users. Very useful for team work/debug! Screen commands (within screen) All screen commands start with Ctrl-a. Ctrl-a ? help and summary of functions Ctrl-a c create an new window (terminal) Ctrl-a Ctrl-n and Ctrl-a Ctrl-p to switch to the next or previous window in the list, by number. Ctrl-a Ctrl-N where N is a number from 0 to 9, to switch to the corresponding window. Ctrl-a " to get a navigable list of running windows Ctrl-a a to clear a missed Ctrl-a Ctrl-a Ctrl-d to disconnect and leave the session running in the background Ctrl-a x lock the screen terminal with a password Ctrl-a [ enter into scrollback mode, exit with esc. Use echo "defscrollback 5000" > ~/.screenrc to increase buffer (default is 100) C-u Scrolls a half page up C-b Scroll a full page up C-d Scroll a half page down C-f Scroll a full page down / Search forward ? Search backward The screen session is terminated when the program within the running terminal is closed and you logout from the terminal. Find Some important options: -x (on BSD) -xdev (on Linux) Stay on the same file system (dev in fstab). -exec cmd {} \; Execute the command and replace {} with the full path -iname Like -name but is case insensitive -ls Display information about the file (like ls -la) -size n n is +-n (k M G T P) -cmin n File's status was last changed n minutes ago. find . -type f ! -perm -444 Find files not readable by all find . -type d ! -perm -111 Find dirs not accessible by all find /home/user/ -cmin 10 -print Files created or modified in the last 10 min. find . -name '*.[ch]' | xargs grep -E 'expr' Search 'expr' in this dir and below. find / -name "*.core" | xargs rm Find core dumps and delete them (also try core.*) find / -name "*.core" -print -exec rm {} \; Other syntax Find images and create an archive, iname is not case sensitive. -r for append find . \( -iname "*.png" -o -iname "*.jpg" \) -print -exec tar -rf images.tar {} \; find . -type f -name "*.txt" ! -name README.txt -print Exclude README.txt files find /var/ -size +10M -exec ls -lh {} \; Find large files > 10 MB find /var/ -size +10M -ls This is simpler find . -size +10M -size -50M -print find /usr/ports/ -name work -type d -print -exec rm -rf {} \; Clean the ports Find files with SUID; those file are vulnerable and must be kept secure find / -type f -user root -perm -4000 -exec ls -l {} \; Be careful with xarg or exec as it might or might not honor quotings and can return wrong results when files or directories contain spaces. In doubt use "-print0 | xargs -0" instead of "| xargs". The option -print0 must be the last in the find command. See this nice mini tutorial for find. find . -type f | xargs ls -l Will not work with spaces in names find . -type f -print0 | xargs -0 ls -l Will work with spaces in names find . -type f -exec ls -l '{}' \; Or use quotes '{}' with -exec Miscellaneous which command Show full path name of command time command See how long a command takes to execute time cat Use time as stopwatch. Ctrl-c to stop set | grep $USER List the current environment cal -3 Display a three month calendar date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]] date 10022155 Set date and time whatis grep Display a short info on the command or word whereis java Search path and standard directories for word setenv varname value Set env. variable varname to value (csh/tcsh) export varname="value" set env. variable varname to value (sh/ksh/bash) pwd Print working directory mkdir -p /path/to/dir no error if existing, make parent dirs as needed mkdir -p project/{bin,src,obj,doc/{html,man,pdf},debug/some/more/dirs} rmdir /path/to/dir Remove directory rm -rf /path/to/dir Remove directory and its content (force) rm -- -badchar.txt Remove file whitch starts with a dash (-) cp -la /dir1 /dir2 Archive and hard link files instead of copy cp -lpR /dir1 /dir2 Same for FreeBSD cp unixtoolbox.xhtml{,.bak} Short way to copy the file with a new extension mv /dir1 /dir2 Rename a directory ls -1 list one file per line history | tail -50 Display the last 50 used commands cd - cd to previous ($OLDPWD) directory Check file hashes with openssl. This is a nice alternative to the commands md5sum or sha1sum (FreeBSD uses md5 and sha1) which are not always installed. openssl md5 file.tar.gz Generate an md5 checksum from file openssl sha1 file.tar.gz Generate an sha1 checksum from file openssl rmd160 file.tar.gz Generate a RIPEMD-160 checksum from file Install Software Usually the package manager uses the proxy variable for http/ftp requests. In .bashrc: export http_proxy=http://proxy_server:3128 export ftp_proxy=http://proxy_server:3128 List installed packages rpm -qa List installed packages (RH, SuSE, RPM based) dpkg -l Debian, Ubuntu pkg_info FreeBSD list all installed packages pkg_info -W smbd FreeBSD show which package smbd belongs to pkginfo Solaris Add/remove software Front ends: yast2/yast for SuSE, redhat-config-packages for Red Hat. rpm -i pkgname.rpm install the package (RH, SuSE, RPM based) rpm -e pkgname Remove package SuSE zypper (see doc and cheet sheet) zypper refresh Refresh repositorie zypper install vim Install the package vim zypper remove vim Remove the package vim zypper search vim Search packages with vim zypper update vim Search packages with vim Debian apt-get update First update the package lists apt-get install emacs Install the package emacs dpkg --remove emacs Remove the package emacs dpkg -S file find what package a file belongs to Gentoo Gentoo uses emerge as the heart of its "Portage" package management system. emerge --sync First sync the local portage tree emerge -u packagename Install or upgrade a package emerge -C packagename Remove the package revdep-rebuild Repair dependencies Solaris The cdrom path is usually /cdrom/cdrom0. pkgadd -d cdrom/Solaris_9/Product SUNWgtar pkgadd -d SUNWgtar Add downloaded package (bunzip2 first) pkgrm SUNWgtar Remove the package FreeBSD pkg_add -r rsync Fetch and install rsync. pkg_delete /var/db/pkg/rsync-xx Delete the rsync package Set where the packages are fetched from with the PACKAGESITE variable. For example: export PACKAGESITE=ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages/Latest/ or ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages-6-stable/Latest/ FreeBSD ports The port tree /usr/ports/ is a collection of software ready to compile and install (see man ports). The ports are updated with the program portsnap. portsnap fetch extract Create the tree when running the first time portsnap fetch update Update the port tree cd /usr/ports/net/rsync/ Select the package to install make install distclean Install and cleanup (also see man ports) make package Make a binary package of this port pkgdb -F Fix the package registry database portsclean -C -DD Clean workdir and distdir (part of portupgrade) OS X MacPorts (use sudo for all commands) port selfupdate Update the port tree (safe) port installed List installed ports port deps apache2 List dependencies for this port port search pgrep Search for string port install proctools Install this package port variants ghostscript List variants of this port port -v install ghostscript +no_x11-no_x11 for negative value port clean --all ghostscript Clean workdir of port port upgrade ghostscript Upgrade this port port uninstall ghostscript Uninstall this port port -f uninstall installed Uninstall everything Library path Due to complex dependencies and runtime linking, programs are difficult to copy to an other system or distribution. However for small programs with little dependencies, the missing libraries can be copied over. The runtime libraries (and the missing one) are checked with ldd and managed with ldconfig. ldd /usr/bin/rsync List all needed runtime libraries otool -L /usr/bin/rsync OS X equivalent to ldd ldconfig -n /path/to/libs/ Add a path to the shared libraries directories ldconfig -m /path/to/libs/ FreeBSD LD_LIBRARY_PATH The variable set the link library path Convert Media Sometimes one simply need to convert a video, audio file or document to another format. Text encoding Text encoding can get totally wrong, specially when the language requires special characters like àäç. The command iconv can convert from one encoding to an other. iconv -f from_encoding -t to_encoding input_file iconv -f ISO8859-1 -t UTF-8 -o file.input > file_utf8 iconv -l List known coded character sets Without the -f option, iconv will use the local char-set, which is usually fine if the document displays well. Unix - DOS newlines Convert DOS (CR/LF) to Unix (LF) newlines and back within a Unix shell. See also dos2unix and unix2dos if you have them. sed 's/.$//' dosfile.txt > unixfile.txt DOS to UNIX awk '{sub(/\r$/,"");print}' dosfile.txt > unixfile.txt DOS to UNIX awk '{sub(/$/,"\r");print}' unixfile.txt > dosfile.txt UNIX to DOS Convert Unix to DOS newlines within a Windows environment. Use sed or awk from mingw or cygwin. sed -n p unixfile.txt > dosfile.txt awk 1 unixfile.txt > dosfile.txt UNIX to DOS (with a cygwin shell) PDF to Jpeg and concatenate PDF files Convert a PDF document with gs (GhostScript) to jpeg (or png) images for each page. Also much shorter with convert and mogrify (from ImageMagick or GraphicsMagick). gs -dBATCH -dNOPAUSE -sDEVICE=jpeg -r150 -dTextAlphaBits=4 -dGraphicsAlphaBits=4 \ -dMaxStripSize=8192 -sOutputFile=unixtoolbox_%d.jpg unixtoolbox.pdf convert unixtoolbox.pdf unixtoolbox-%03d.png convert *.jpeg images.pdf Create a simple PDF with all pictures convert image000* -resample 120x120 -compress JPEG -quality 80 images.pdf mogrify -format png *.ppm convert all ppm images to png format Ghostscript can also concatenate multiple pdf files into a single one. This only works well if the PDF files are "well behaved". gs -q -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=all.pdf \ file1.pdf file2.pdf ... On Windows use '#' instead of '=' Convert video Compress the Canon digicam video with an mpeg4 codec and repair the crappy sound. mencoder -o videoout.avi -oac mp3lame -ovc lavc -srate 11025 \ -channels 1 -af-adv force=1 -lameopts preset=medium -lavcopts \ vcodec=msmpeg4v2:vbitrate=600 -mc 0 vidoein.AVI See sox for sound processing. Copy an audio cd The program cdparanoia can save the audio tracks (FreeBSD port in audio/cdparanoia/), oggenc can encode in Ogg Vorbis format, lame converts to mp3. cdparanoia -B Copy the tracks to wav files in current dir lame -b 256 in.wav out.mp3 Encode in mp3 256 kb/s for i in *.wav; do lame -b 256 $i `basename $i .wav`.mp3; done oggenc in.wav -b 256 out.ogg Encode in Ogg Vorbis 256 kb/s Printing Print with lpr lpr unixtoolbox.ps Print on default printer export PRINTER=hp4600 Change the default printer lpr -Php4500 #2 unixtoolbox.ps Use printer hp4500 and print 2 copies lpr -o Duplex=DuplexNoTumble ... Print duplex along the long side lpr -o PageSize=A4,Duplex=DuplexNoTumble ... lpq Check the queue on default printer lpq -l -Php4500 Queue on printer hp4500 with verbose lprm - Remove all users jobs on default printer lprm -Php4500 3186 Remove job 3186. Find job nbr with lpq lpc status List all available printers lpc status hp4500 Check if printer is online and queue length Some devices are not postscript and will print garbage when fed with a pdf file. This might be solved with: gs -dSAFER -dNOPAUSE -sDEVICE=deskjet -sOutputFile=\|lpr file.pdf Print to a PDF file even if the application does not support it. Use gs on the print command instead of lpr. gs -q -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=/path/file.pdf Databases PostgreSQL Change root or a username password psql -d template1 -U pgsql > alter user pgsql with password 'pgsql_password'; Use username instead of "pgsql" Create user and database The commands createuser, dropuser, createdb and dropdb are convenient shortcuts equivalent to the SQL commands. The new user is bob with database bobdb ; use as root with pgsql the database super user: createuser -U pgsql -P bob -P will ask for password createdb -U pgsql -O bob bobdb new bobdb is owned by bob dropdb bobdb Delete database bobdb dropuser bob Delete user bob The general database authentication mechanism is configured in pg_hba.conf Grant remote access The file $PGSQL_DATA_D/postgresql.conf specifies the address to bind to. Typically listen_addresses = '*' for Postgres 8.x. The file $PGSQL_DATA_D/pg_hba.conf defines the access control. Examples: TYPE DATABASE USER IP-ADDRESS IP-MASK METHOD host bobdb bob <IP_ADDRESS> <IP_ADDRESS> password host all all <IP_ADDRESS>/0 password Backup and restore The backups and restore are done with the user pgsql or postgres. Backup and restore a single database: pg_dump --clean dbname > dbname_sql.dump psql dbname < dbname_sql.dump Backup and restore all databases (including users): pg_dumpall --clean > full.dump psql -f full.dump postgres In this case the restore is started with the database postgres which is better when reloading an empty cluster. MySQL Change mysql root or username password Method 1 /etc/init.d/mysql stop or killall mysqld mysqld --skip-grant-tables mysqladmin -u root password 'newpasswd' /etc/init.d/mysql start Method 2 mysql -u root mysql mysql> UPDATE USER SET PASSWORD=PASSWORD("newpassword") where user='root'; mysql> FLUSH PRIVILEGES; Use username instead of "root" mysql> quit Create user and database (see MySQL doc) mysql -u root mysql mysql> CREATE USER 'bob'@'localhost' IDENTIFIED BY 'pwd'; create only a user mysql> CREATE DATABASE bobdb; mysql> GRANT ALL ON *.* TO 'bob'@'%' IDENTIFIED BY 'pwd'; Use localhost instead of % to restrict the network access mysql> DROP DATABASE bobdb; Delete database mysql> DROP USER bob; Delete user mysql> DELETE FROM mysql.user WHERE user='bob and host='hostname'; Alt. command mysql> FLUSH PRIVILEGES; Grant remote access Remote access is typically permitted for a database, and not all databases. The file /etc/my.cnf contains the IP address to bind to. (On FreeBSD my.cnf not created per fedault, copy one .cnf file from /usr/local/share/mysql to /usr/local/etc/my.cnf) Typically comment the line bind-address = out. mysql -u root mysql mysql> GRANT ALL ON bobdb.* TO<EMAIL_ADDRESS>IDENTIFIED BY 'PASSWORD'; mysql> REVOKE GRANT OPTION ON foo.* FROM<EMAIL_ADDRESS>mysql> FLUSH PRIVILEGES; Use 'hostname' or also '%' for full access Backup and restore Backup and restore a single database: mysqldump -u root -psecret --add-drop-database dbname > dbname_sql.dump mysql -u root -psecret -D dbname < dbname_sql.dump Backup and restore all databases: mysqldump -u root -psecret --add-drop-database --all-databases > full.dump mysql -u root -psecret < full.dump Here is "secret" the mysql root password, there is no space after -p. When the -p option is used alone (w/o password), the password is asked at the command prompt. SQLite SQLite is a small powerful self-contained, serverless, zero-configuration SQL database. Dump and restore It can be useful to dump and restore an SQLite database. For example you can edit the dump file to change a column attribute or type and then restore the database. This is easier than messing with SQL commands. Use the command sqlite3 for a 3.x database. sqlite database.db .dump > dump.sql dump sqlite database.db < dump.sql restore Convert 2.x to 3.x database sqlite database_v2.db .dump | sqlite3 database_v3.db Disk Quota A disk quota allows to limit the amount of disk space and/or the number of files a user or (or member of group) can use. The quotas are allocated on a per-file system basis and are enforced by the kernel. Linux setup The quota tools package usually needs to be installed, it contains the command line tools. Activate the user quota in the fstab and remount the partition. If the partition is busy, either all locked files must be closed, or the system must be rebooted. Add usrquota to the fstab mount options, for example: /dev/sda2 /home reiserfs rw,acl,user_xattr,usrquota 1 1 mount -o remount /home mount Check if usrquota is active, otherwise reboot Initialize the quota.user file with quotacheck. quotacheck -vum /home chmod 644 /home/aquota.user To let the users check their own quota Activate the quota either with the provided script (e.g. /etc/init.d/quotad on SuSE) or with quotaon: quotaon -vu /home Check that the quota is active with: quota -v FreeBSD setup The quota tools are part of the base system, however the kernel needs the option quota. If it is not there, add it and recompile the kernel. options QUOTA As with Linux, add the quota to the fstab options (userquota, not usrquota): /dev/ad0s1d /home ufs rw,noatime,userquota 2 2 mount /home To remount the partition Enable disk quotas in /etc/rc.conf and start the quota. grep quotas /etc/rc.conf enable_quotas="YES" turn on quotas on startup (or NO). check_quotas="YES" Check quotas on startup (or NO). /etc/rc.d/quota start Assign quota limits The quotas are not limited per default (set to 0). The limits are set with edquota for single users. A quota can be also duplicated to many users. The file structure is different between the quota implementations, but the principle is the same: the values of blocks and inodes can be limited. Only change the values of soft and hard. If not specified, the blocks are 1k. The grace period is set with edquota -t. For example: edquota -u colin Linux Disk quotas for user colin (uid 1007): Filesystem blocks soft hard inodes soft hard /dev/sda8 108 1000 2000 1 0 0 FreeBSD Quotas for user colin: /home: kbytes in use: 504184, limits (soft = 700000, hard = 800000) inodes in use: 1792, limits (soft = 0, hard = 0) For many users The command edquota -p is used to duplicate a quota to other users. For example to duplicate a reference quota to all users: edquota -p refuser `awk -F: '$3 > 499 {print $1}' /etc/passwd` edquota -p refuser user1 user2 Duplicate to 2 users Checks Users can check their quota by simply typing quota (the file quota.user must be readable). Root can check all quotas. quota -u colin Check quota for a user repquota /home Full report for the partition for all users Shells Most Linux distributions use the bash shell while the BSDs use tcsh, the bourne shell is only used for scripts. Filters are very useful and can be piped: grep Pattern matching sed Search and Replace strings or characters cut Print specific columns from a marker sort Sort alphabetically or numerically uniq Remove duplicate lines from a file For example used all at once: ifconfig | sed 's/ / /g' | cut -d" " -f1 | uniq | grep -E "[a-z0-9]+" | sort -r ifconfig | sed '/.*inet addr:/!d;s///;s/ .*//'|sort -t. -k1,1n -k2,2n -k3,3n -k4,4n The first character in the sed pattern is a tab. To write a tab on the console, use ctrl-v ctrl-tab. bash Redirects and pipes for bash and sh: cmd 1> file Redirect stdout to file. cmd 2> file Redirect stderr to file. cmd 1>> file Redirect and append stdout to file. cmd &> file Redirect both stdout and stderr to file. cmd >file 2>&1 Redirects stderr to stdout and then to file. cmd1 | cmd2 pipe stdout to cmd2 cmd1 2>&1 | cmd2 pipe stdout and stderr to cmd2 Modify your configuration in ~/.bashrc (it can also be ~/.bash_profile). The following entries are useful, reload with ". .bashrc". With cygwin use ~/.bash_profile; with rxvt past with shift + left-click. in .bashrc bind '"\e[A"':history-search-backward Use up and down arrow to search bind '"\e[B"':history-search-forward the history. Invaluable! set -o emacs Set emacs mode in bash (see below) set bell-style visible Do not beep, inverse colors Set a nice prompt like [user@host]/path/todir> PS1="\[\033[1;30m\][\[\033[1;34m\]\u\[\033[1;30m\]" PS1="$PS1@\[\033[0;33m\]\h\[\033[1;30m\]]\[\033[0;37m\]" PS1="$PS1\w\[\033[1;30m\]>\[\033[0m\]" To check the currently active aliases, simply type alias alias ls='ls -aF' Append indicator (one of */=>@|) alias ll='ls -aFls' Listing alias la='ls -all' alias ..='cd ..' alias ...='cd ../..' export HISTFILESIZE=5000 Larger history export CLICOLOR=1 Use colors (if possible) export LSCOLORS=ExGxFxdxCxDxDxBxBxExEx tcsh Redirects and pipes for tcsh and csh (simple > and >> are the same as sh): cmd >& file Redirect both stdout and stderr to file. cmd >>& file Append both stdout and stderr to file. cmd1 | cmd2 pipe stdout to cmd2 cmd1 |& cmd2 pipe stdout and stderr to cmd2 The settings for csh/tcsh are set in ~/.cshrc, reload with "source .cshrc". Examples: in .cshrc alias ls 'ls -aF' alias ll 'ls -aFls' alias la 'ls -all' alias .. 'cd ..' alias ... 'cd ../..' set prompt = "%B%n%b@%B%m%b%/> " like user@host/path/todir> set history = 5000 set savehist = ( 6000 merge ) set autolist Report possible completions with tab set visiblebell Do not beep, inverse colors Bindkey and colors bindkey -e Select Emacs bindings Use emacs keys to edit the command prompt bindkey -k up history-search-backward Use up and down arrow to search bindkey -k down history-search-forward setenv CLICOLOR 1 Use colors (if possible) setenv LSCOLORS ExGxFxdxCxDxDxBxBxExEx The emacs mode enables to use the emacs keys shortcuts to modify the command prompt line. This is extremely useful (not only for emacs users).  Scripting Basics | Script example | awk | sed | Regular Expressions | useful commands The Bourne shell (/bin/sh) is present on all Unix installations and scripts written in this language are (quite) portable; man 1 sh is a good reference. Basics Variables and arguments Assign with variable=value and get content with $variable MESSAGE="Hello World" Assign a string PI=3.1415 Assign a decimal number N=8 TWON=`expr $N * 2` Arithmetic expression (only integers) TWON=$(($N * 2)) Other syntax TWOPI=`echo "$PI * 2" | bc -l` Use bc for floating point operations ZERO=`echo "c($PI/4)-sqrt(2)/2" | bc -l` The command line arguments are $0, $1, $2, ... $0 is the command itself $ The number of arguments $* All arguments (also $@) Special Variables $$ The current process ID $? exit status of last command command if [ $? != 0 ]; then echo "command failed" fi mypath=`pwd` mypath=${mypath}/file.txt echo ${mypath##*/} Display the filename only echo ${mypath%%.*} Full path without extention var2=${var:=string} Use var if set, otherwise use string assign string to var and then to var2. Constructs for file in `ls` do echo $file done count=0 while [ $count -lt 5 ]; do echo $count sleep 1 count=$(($count + 1)) done myfunction() { find . -type f -name "*.$1" -print $1 is first argument of the function } myfunction "txt" Generate a file MYHOME=/home/colin cat > testhome.sh << _EOF All of this goes into the file testhome.sh if [ -d "$MYHOME" ] ; then echo $MYHOME exists else echo $MYHOME does not exist fi _EOF sh testhome.sh Bourne script example As a small example, the script used to create a PDF booklet from this xhtml document: #!/bin/sh This script creates a book in pdf format ready to print on a duplex printer if [ $-ne 1 ]; then Check the argument echo 1>&2 "Usage: $0 HtmlFile" exit 1 non zero exit if error fi file=$1 Assign the filename fname=${file%.*} Get the name of the file only fext=${file#*.} Get the extension of the file prince $file -o $fname.pdf from www.princexml.com pdftops -paper A4 -noshrink $fname.pdf $fname.ps create postscript booklet cat $fname.ps |psbook|psnup -Pa4 -2 |pstops -b "2:0,1U(21cm,29.7cm)" > $fname.book.ps ps2pdf13 -sPAPERSIZE=a4 -sAutoRotatePages=None $fname.book.ps $fname.book.pdf use #a4 and #None on Windows! exit 0 exit 0 means successful Some awk commands Awk is useful for field stripping, like cut in a more powerful way. Search this document for other examples. See for example gnulamp.com and one-liners for awk for some nice examples. awk '{ print $2, $1 }' file Print and inverse first two columns awk '{printf("%5d : %s\n", NR,$0)}' file Add line number left aligned awk '{print FNR "\t" $0}' files Add line number right aligned awk NF test.txt remove blank lines (same as grep '.') awk 'length > 80' print line longer than 80 char) Some sed commands Here is the one liner gold mine. And a good introduction and tutorial to sed. sed 's/string1/string2/g' Replace string1 with string2 sed -i 's/wroong/wrong/g' *.txt Replace a recurring word with g sed 's/\(.*\)1/\12/g' Modify anystring1 to anystring2 sed '/ /,/<\/p>/d' t.xhtml Delete lines that start with
and end with