Hardware | Statistics | Users | Limits | Runlevels | root password | Compile kernel | Repair grub
Running kernel and 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 versionUse /etc/
DISTR-release with DISTR= lsb (Ubuntu), redhat, gentoo, mandrake, sun (Solaris), and so on. See also /etc/issue.
# 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) # man hier # Description of the file system hierarchy # 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
# 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
# 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
# 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
# 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 adminEncrypted 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.# echo "Sorry no login now" > /etc/nologin # (Linux) # echo "Sorry no login now" > /var/run/nologin # (FreeBSD)
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.
/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
/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
limits in csh or tcsh or as in Linux, use ulimit in an sh or bash shell.
/etc/login.conf. An unlimited value is still limited by the system maximal value.
/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 statisticsSee The FreeBSD handbook Chapter 11http://www.freebsd.org/handbook/configtuning-kernel-limits.html for details.
/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
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.# 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
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 runlevelsDebian 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
/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 # RebootThe process
init can also be used to reach one of the following states level. For example # init 6 for reboot.
USR2)TERM)INT)TSTP)HUP)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.
init=/bin/shThe 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.# mount -o remount,rw / # passwd # or delete the root password (/etc/shadow) # sync; mount -o remount,ro / # sync before to remount read only # reboot
# mount -u /; mount -a # will mount / rw
# passwd
# reboot
# mount -o rw /dev/ad4s3a /mnt
# chroot /mnt # chroot into /mnt
# passwd
# reboot
# lsmod # List all modules loaded in the kernel # modprobe isdn # To load a module (here isdn)
# kldstat # List all modules loaded in the kernel # kldload crypto # To load a module (here crypto)
# 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
/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-allTo 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=MYKERNELTo 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 # rebootFor 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
/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
Listing | Priority | Background/Foreground | Top | Kill
ps.
# ps -auxefw # Extensive list of all running process
However more typical usage is with a pipe or with pgrep:
# 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 $$ # The PID of your shell # fuser -va 22/tcp # List processes using port 22 (Linux) # pmap PID # Memory map of process (hunt memory leaks) (Linux) # fuser -va /home # List processes accessing the /home partition # strace df # Trace system calls and signals # truss df # same as above on FreeBSD/Solaris/Unixware
renice. Negative numbers have a higher priority, the lowest is -20 and "nice" have a positive value.
# renice -5 586 # Stronger priority
586: old priority 0, new priority -5
Start the process with a defined priority with nice. Positive is "nice" or weak, negative is strong scheduling priority. Make sure you know if /usr/bin/nice or the shell built-in is used (check with # which nice).
# nice -n -5 top # Stronger priority (/usr/bin/nice) # nice -n 5 top # Weaker priority (/usr/bin/nice) # nice +5 top # tcsh builtin nice (same as above!)While nice changes the CPU scheduler, an other useful command
ionice will schedule the disk IO. This is very useful for intensive IO application (e.g. compiling). You can select a class (idle - best effort - real time), the man page is short and well explained.
# ionice c3 -p123 # set idle class for pid 123 (Linux only) # ionice -c2 -n0 firefox # Run firefox with best effort and high priority # ionice -c3 -p$$ # Set the actual shell to idle priorityThe last command is very useful to compile (or debug) a large project. Every command launched from this shell will have a lover priority.
$$ is your shell pid (try echo $$).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
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 foregroundUse
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 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:
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:
HUP (hang up)INT (interrupt)QUIT (quit)KILL (non-catchable, non-ignorable kill)TERM (software termination signal)Disk info | Boot | Disk usage | Opened files | Mount/remount | Mount SMB | Mount image | Burn ISO | Create image | Memory disk | Disk performance
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
# 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
# unload # load kernel.old # boot
# 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)
# 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
# umount /home/
umount: unmount of /home # umount impossible because a file is locking home
failed: Device busy
# fstat -f /home # for a mount point # fstat -p PID # for an application with PID # fstat -u user # for a user nameFind 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
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 /cdromOr find the device in /dev/ or with dmesg
# mount -v -t cd9660 /dev/cd0c /mnt # cdrom # mount_cd9660 /dev/wcd0c /cdrom # other method # mount -v -t msdos /dev/fd0c /mnt # floppyEntry in /etc/fstab:
# Device Mountpoint FStype Options Dump Pass# /dev/acd0 /cdrom cd9660 ro,noauto 0 0To let users do it:
# sysctl vfs.usermount=1 # Or insert the line "vfs.usermount=1" in /etc/sysctl.conf
# 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 SCSIEntry in /etc/fstab:
/dev/cdrom /media/cdrom subfs noauto,fs=cdfss,ro,procuid,nosuid,nodev,exec 0 0
# 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
# mount -o remount,ro / # Linux # mount -o ro / # FreeBSDCopy the raw data from a cdrom into an iso image:
# dd if=/dev/cd0c of=file.iso
# 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
# smbclient -U user -I 192.168.16.229 -L //smbshare/ # List the shares
# mount -t smbfs -o username=winuser //smbserver/myshare /mnt/smbshare
# mount -t cifs -o username=winuser,password=winpwd //192.168.16.229/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=winpwdAnd mount as follow:
# mount -t cifs -o credentials=/home/user/.smb //192.168.16.229/myshare /mnt/smbshare
# smbutil view -I 192.168.16.229 //winuser@smbserver # List the shares
# mount_smbfs -I 192.168.16.229 //winuser@smbserver/myshare /mnt/smbshare
# 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
# 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
# lofiadm -a file.iso
# mount -F hsfs -o ro /dev/lofi/1 /mnt
# umount /mnt; lofiadm -d /dev/lofi/1 # Cleanup the lofi device
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=notruncUse 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/dirOn FreeBSD, mkisofs is found in the ports in sysutils/cdrtools.
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
cdrecord with Linux as described above. Additionally it is possible to use the native ATAPI interface which is found with:
# cdrecord dev=ATAPI -scanbusAnd burn the CD/DVD as above.
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 18.7http://www.freebsd.org/handbook/creating-dvds.html.
# -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
# dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300
bchunk programhttp://freshmeat.net/projects/bchunk/ can do this. It is in the FreeBSD ports in sysutils/bchunk.
# bchunk imagefile.bin imagefile.cue imagefile.iso
# 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 deviceThe 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).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 0It 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
# 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
/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
# 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
# mount -t tmpfs -osize=64m tmpfs /memdisk
# 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
Routing | Additional IP | Change MAC | Ports | Firewall | IP Forward | NAT | DNS | DHCP | Traffic | QoS | NIS | Netcat
# 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
# 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 protocolAdditional commands which are not always installed per default but easy to find:
# arping 192.168.16.254 # Ping on ethernet layer # tcptraceroute -f 5 cb.vu # uses tcp instead of icmp to trace through firewalls
# route -n # Linux or use "ip route" # netstat -rn # Linux, BSD and UNIX # route print # Windows
# route add 212.117.0.0/16 192.168.1.1 # route delete 212.117.0.0/16 # route add default 192.168.1.1Add the route permanently in /etc/rc.conf
static_routes="myroute" route_myroute="-net 212.117.0.0/16 192.168.1.1"
# route add -net 192.168.20.0 netmask 255.255.255.0 gw 192.168.16.254 # ip route add 192.168.20.0/24 via 192.168.16.254 # same as above with ip route # route add -net 192.168.20.0 netmask 255.255.255.0 dev eth0 # route add default gw 192.168.51.254 # ip route add default via 192.168.51.254 dev eth0 # same as above with ip route # route delete -net 192.168.20.0 netmask 255.255.255.0
# route add -net 192.168.20.0 -netmask 255.255.255.0 192.168.16.254
# route add default 192.168.51.254 1 # 1 = hops to the next gateway
# route change default 192.168.50.254 1
Permanent entries are set in entry in /etc/defaultrouter.
# Route add 192.168.50.0 mask 255.255.255.0 192.168.51.253 # Route add 0.0.0.0 mask 0.0.0.0 192.168.51.254Use add -p to make the route persistent.
# ifconfig eth0 192.168.50.254 netmask 255.255.255.0 # First IP # ifconfig eth0:0 192.168.51.254 netmask 255.255.255.0 # Second IP # ip addr add 192.168.50.254/24 dev eth0 # Equivalent ip commands # ip addr add 192.168.51.254/24 dev eth0 label eth0:1
# ifconfig fxp0 inet 192.168.50.254/24 # First IP # ifconfig fxp0 alias 192.168.51.254 netmask 255.255.255.0 # Second IP # ifconfig fxp0 -alias 192.168.51.254 # Remove second IP aliasPermanent entries in /etc/rc.conf
ifconfig_fxp0="inet 192.168.50.254 netmask 255.255.255.0" ifconfig_fxp0_alias0="192.168.51.254 netmask 255.255.255.0"
ifconfig -a
# ifconfig hme0 plumb # Enable the network card # ifconfig hme0 192.168.50.254 netmask 255.255.255.0 up # First IP # ifconfig hme0:1 192.168.51.254 netmask 255.255.255.0 up # Second IP
# 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 # Mac OS X Tiger # sudo ifconfig en0 lladdr 00:01:02:03:04:05 # Mac OS X LeopardMany tools exist for Windows. For example etherchangehttp://ntsecurity.nu/toolbox/etherchange. Or look for "Mac Makeup", "smac".
# 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
# 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
# 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
# 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
# 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.
# ndd -set /dev/ip ip_forwarding 1 # Set IP forward 0=off, 1=on
# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # to activate NAT # iptables -t nat -A PREROUTING -p tcp -d 78.31.70.238 --dport 20022 -j DNAT \ --to 192.168.16.44:22 # Port forward 20022 to internal IP port ssh # iptables -t nat -A PREROUTING -p tcp -d 78.31.70.238 --dport 993:995 -j DNAT \ --to 192.168.16.254:993-995 # Port forward of range 993-995 # ip route flush cache # iptables -L -t nat # Check NAT statusDelete the port forward with -D instead of -A. The program netstat-nathttp://tweegy.nl/projects/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
# 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 192.168.51.103:7777 7777
nameserver 78.31.70.238 search sleepyowl.net intern.lab domain sleepyowl.netCheck the system domain name with:
# hostname -d # Same as dnsdomainname
# ipconfig /? # Display help # ipconfig /all # See all information including DNS
# /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
213.133.105.2 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 78.31.70.238 ;; SERVER: 192.168.51.254#53(192.168.51.254)The router 192.168.51.254 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 @127.0.0.1 NS sun.com # To test the local server # dig @204.97.212.10 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
dig, host and nslookup:
# dig -x 78.31.70.238 # host 78.31.70.238 # nslookup 78.31.70.238
named locally to resolve the hostname queries. The format is simple, for example:
78.31.70.238 sleepyowl.net sleepyowlThe 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
# dhcpcd -n eth0 # Trigger a renew (does not always work) # dhcpcd -k eth0 # release and shutdownThe lease with the full information is stored in:
/var/lib/dhcpcd/dhcpcd-eth0.info
# dhclient bge0The lease with the full information is stored in:
/var/db/dhclient.leases.bge0Use
/etc/dhclient.confto prepend options or force different options:
# cat /etc/dhclient.conf
interface "rl0" {
prepend domain-name-servers 127.0.0.1;
default domain-name "sleepyowl.net";
supersede domain-name "sleepyowl.net";
}
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!
# tcpdump -nl -i bge0 not port ssh and src \(192.168.16.121 or 192.168.16.54\) # tcpdump -n -i eth1 net 192.168.16.121 # select to/from a single IP # tcpdump -n -i eth1 net 192.168.16.0/24 # 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 ASCIIAdditional 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# nmap cb.vu # scans all reserved TCP ports on the host # nmap -sP 192.168.16.0/24 # 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.
# 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
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
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 123.23.0.1 flowid 1:1 # or/and use server IPStatus and remove with
# tc -s qdisc ls dev eth0 # queue status # tc qdisc del dev eth0 root # delete all QoS
# 2^13 (8192) < 10000 < 2^14 (16384) # ending is 2^14 = 16384 # echo "obase=16;(2^14)-1024" | bc # mask is 0x3C00
# 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 123.23.0.1 # or/and use server IP # ipfw add 20 queue 2 dsp-port ssh # ipfw add 30 queue 3 from me to any # all the restStatus and remove with
# ipfw list # rules status # ipfw pipe list # pipe status # ipfw flush # deletes all rules but default
# 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 serverIs 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 1190635041. Mon Sep 24 13:57:21 2007 The master server is servername.domain.net.
# cat /etc/yp.conf ypserver servername domain domain.net broadcast
netcat instead of nc. Also see the similar command socat.
server# tar -cf - -C VIDEO_TS . | nc -l -p 4444 # Serve tar folder on port 4444 client# nc 192.168.1.1 4444 | tar xpf - -C VIDEO_TS # Pull the file on port 4444 server# cat largefile | nc -l 5678 # Server a single file client# nc 192.168.1.1 5678 > largefile # Pull the single file server# dd if=/dev/da0 | nc -l 4444 # Server partition image client# nc 192.168.1.1 4444 | dd of=/dev/da0 # Pull partition to clone client# nc 192.168.1.1 4444 | dd of=da0.img # Pull partition to file
# nc -lp 4444 -e /bin/bash # Provide a remote shell (server backdoor) # nc -lp 4444 -e cmd.exe # remote shell for Windows
# while true; do nc -l -p 80 < unixtoolbox.xhtml; done
alice# nc -lp 4444 bob # nc 192.168.1.1 4444
Public key | Fingerprint | SCP | Tunneling
# mkdir -p /home/USER/.ssh
~/.ssh/id_dsa is the private key, ~/.ssh/id_dsa.pub is the public key.~/.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"
# cd ~/.ssh # ssh-keygen -i -f keyfilename.pub >> authorized_keys2
# scp .ssh/puttykey.pub root@192.168.51.254:.ssh/
# cd ~/.ssh # ssh-keygen -i -f puttykey.pub >> authorized_keys2
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.pubNow the client connecting to this server can verify that he is connecting to the right server:
# ssh linda The authenticity of host 'linda (192.168.16.54)' 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
# scp file.txt host-two:/tmp # scp joe@host-two:/www/*.html /www/tmp # scp -r joe@host-two:/www /www/tmpIn 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.
ssh_exchange_identification: Connection closed by remote hostWith this error try the following on the server:
echo 'SSHD: ALL' >> /etc/hosts.allow /etc/init.d/sshd restart
# 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 forwardingThis 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.
# ssh -L 2401:localhost:2401 -L 8080:localhost:80 user@gate
# ssh -L 139:smbserver:139 -L 3388:smbserver:3389 user@gateThe smb share can now be accessed with \\127.0.0.1\, but only if the local share is disabled, because the local share is listening on port 139.
# 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
# ssh -R 15900:localhost:5900 user@gateOn client cliadmin (from host to gate):
# ssh -L 5900:localhost:15900 admin@gateNow the admin can connect directly to the client VNC with:
# vncconnect -display :0 localhost
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
# 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
-L or -R tunnels on one line.
#!/bin/sh COMMAND="ssh -N -f -g -R 3022:localhost:22 colin@cb.vu" pgrep -f -x "$COMMAND" > /dev/null 2>&1 || $COMMAND exit 0
1 * * * * colin /home/colin/port_forward.sh # crontab entry (here hourly)
PermitRootLogin yes PermitTunnel yes
cli># ssh -w5:5 root@hserver srv># ifconfig tun5 10.0.1.1 netmask 255.255.255.252 # Executed on the server shell
cli># ssh -w5:5 root@hserver srv># ifconfig tun5 10.0.1.1 10.0.1.2 # Executed on the server shell
cli># ifconfig tun5 10.0.1.2 netmask 255.255.255.252 # Client is on Linux cli># ifconfig tun5 10.0.1.2 10.0.1.1 # Client is on FreeBSDThe two hosts are now connected and can transparently communicate with any layer 3/4 protocol using the tunnel IP addresses.
gateA># ssh -w5:5 root@gateB gateB># ifconfig tun5 10.0.1.1 netmask 255.255.255.252 # Executed on the gateB shell gateB># route add -net 192.168.51.0 netmask 255.255.255.0 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
gateA># ssh -w5:5 root@gateB # Creates the tun5 devices gateB># ifconfig tun5 10.0.1.1 10.0.1.2 # Executed on the gateB shell gateB># route add 192.168.51.0/24 10.0.1.2 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
gateA># ifconfig tun5 10.0.1.2 netmask 255.255.255.252 gateA># route add -net 192.168.16.0 netmask 255.255.255.0 dev tun5 gateA># echo 1 > /proc/sys/net/ipv4/ip_forward gateA># iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
gateA># ifconfig tun5 10.0.1.2 10.0.1.1 gateA># route add 192.168.16.0/24 10.0.1.2 gateA># sysctl net.inet.ip.forwarding=1 gateA># natd -s -m -u -dynamic -n fxp0 # see NAT gateA># sysctl net.inet.ip.fw.enable=1The 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 -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 shellExclude 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 beforersync and ssh are available in a Windows command shell.
# 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 copyNow test it with (in one line):
rsync -rv "/cygdrive/c/Documents and Settings/%USERNAME%/My Documents/" \ 'user@server:My\ Documents/'
@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 /etc/init.d/dhcpd restart # Run the rc script as root # sudo -u sysadmin whoami # Run cmd as an other user
/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 rightshosts 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)# cat /etc/sudoers # Host aliases are subnets or hostnames. Host_Alias DMZ = 212.118.81.40/28 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
# openssl aes-128-cbc -salt -in file -out file.aes # openssl aes-128-cbc -d -salt -in file.aes -out fileNote that the file can of course be a tar archive.
# 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 -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
# gpg -c file # Encrypt file with password # gpg file.gpg # Decrypt file (optionally -o otherfile)
# gpg --gen-key # This can take a long time
The keys are stored in ~/.gnupg/ on Unix, on Windows they are typically stored in~/.gnupg/pubring.gpg # Contains your public keys and all others imported ~/.gnupg/secring.gpg # Can contain more than one private keyShort reminder on most used options:
# 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
# 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.
# 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)
Linux with LUKS | Linux dm-crypt only | FreeBSD GELI | FBSD pwd only
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.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.
# cryptsetup --help, if nothing about LUKS shows up, use the instructions below Without LUKS. First create a partition if necessary: fdisk /dev/sdc.
# 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
# cryptsetup luksOpen /dev/sdc1 sdc1 # mount -t ext3 /dev/mapper/sdc1 /mnt
# umount /mnt # cryptsetup luksClose sdc1
# 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 partitionDo 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.
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 18.6http://www.freebsd.org/handbook/disks-encrypting.html 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
/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.
# 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
# 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
# umount /mnt # geli detach /dev/ad1.eli
# 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
/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.eliIt 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
[ 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).
# openssl req -new -x509 -days 730 -config /etc/ssl/openssl.cnf \ -keyout CA/private/cakey.pem -out CA/cacert.pem
-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.
# 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.pemNow servernamekey.pem is the private key and servernamecert.pem is the server certificate.
-----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/:
# 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
Server setup | CVS test | SSH tunneling | CVS usage
# 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 changesAdd 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.
cvspserver stream tcp nowait cvs /usr/bin/cvs cvs \ --allow-root=/usr/local/cvs pserverIt 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.
# 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
# cvs -d :pserver:colin@192.168.50.254:/usr/local/cvs login Logging in to :pserver:colin@192.168.50.254:2401/usr/local/cvs CVS password:
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 pserverWhen 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@192.168.50.254:/usr/local/cvs import MyProject MyCompany STARTWhere 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.
# cvs -d :pserver:colin@192.168.50.254:/usr/local/cvs checkout MyProject
or
# setenv CVSROOT :pserver:colin@192.168.50.254:/usr/local/cvs
# cvs checkout MyProject
# 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 CVSon 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 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 wordAfter 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
# 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
# cd /devel/project
# diff -Naur olddir newdir > patchfile # Create a patch from a directory or a file
# diff -Naur oldfile newfile > patchfile
# 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
Server setup | SVN+SSH | SVN over http | SVN usage
Subversion (SVN)http://subversion.tigris.org/ 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 bookhttp://svnbook.red-bean.com/en/1.4/./home/svn/ must exist):
# svnadmin create --fs-type fsfs /home/svn/project1Now 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.# svn import /project1/ file:///home/svn/project1/trunk -m 'Initial import' # svn checkout file:///home/svn/project1The new directory "trunk" is only a convention, this is not required.
file:// with svn+ssh/hostname. For example:
# svn checkout svn+ssh://hostname/home/svn/project1As 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
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/svnCreate a user with htpasswd2:
# htpasswd -c /etc/svn-passwd user1 # -c creates the file
# 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
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'
# 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
less | vi | mail | tar | dd | screen | find | Miscellaneous
less command displays a text document on the console. It is present on most installation.
# less unixtoolbox.xhtmlSome important commands are (^N stands for [control]-[N]):
: help if you are lost.nano and pico are usually available too and are easier (IMHO) to use.
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. Example:
# mail c@cb.vu Subject: Your text is full of typos "For a moment, nothing happened. 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 c@cb.vuThis is also a simple way to test the mail server.
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:
# 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 compressionOnly 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
# 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
# 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 (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# 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.
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.
# dd if=/dev/zero of=/dev/hdc # Delete full disk # dd if=/dev/urandom of=/dev/hdc # Delete full disk better # kill -USR1 PID # View dd progress (Linux) # kill -INFO PID # View dd progress (FreeBSD)
# 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
# screenWithin the screen session we can start a long lasting program (like top).
# topNow detach with Ctrl-a Ctrl-d. Reattach the terminal with:
# screen -R -DIn 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 -xAttach to a running screen in a multi display mode. The console is thus shared among multiple users. Very useful for team work/debug!
-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 findhttp://www.hccfl.edu/pollock/Unix/FindCmd.htm.
# 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
# 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) # 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 commandsCheck 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
export http_proxy=http://proxy_server:3128 export ftp_proxy=http://proxy_server:3128
# 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
# rpm -i pkgname.rpm # install the package (RH, SuSE, RPM based) # rpm -e pkgname # Remove package
# 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
# 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
# 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
/cdrom/cdrom0.
# pkgadd -d <cdrom>/Solaris_9/Product SUNWgtar # pkgadd -d SUNWgtar # Add downloaded package (bunzip2 first) # pkgrm SUNWgtar # Remove the package
# pkg_add -r rsync # Fetch and install rsync. # pkg_delete /var/db/pkg/rsync-xx # Delete the rsync packageSet 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/
/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
ldd and managed with ldconfig.
# ldd /usr/bin/rsync # List all needed runtime libraries # 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
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.
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 DOSConvert 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)
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 formatGhostscript 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 '='
# 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.AVISee sox for sound processing.
cdparanoiahttp://xiph.org/paranoia/ 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
# 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 lengthSome 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.pdfPrint 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
# psql -d template1 -U pgsql
> alter user pgsql with password 'pgsql_password'; # Use username instead of "pgsql"
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 bobThe general database authentication mechanism is configured in pg_hba.conf
$PGSQL_DATA_D/postgresql.conf specifies the address to bind to. Typically listen_addresses = '*' for Postgres 8.x.$PGSQL_DATA_D/pg_hba.conf defines the access control. Examples:
# TYPE DATABASE USER IP-ADDRESS IP-MASK METHOD host bobdb bob 212.117.81.42 255.255.255.255 password host all all 0.0.0.0/0 password
# pg_dump --clean dbname > dbname_sql.dump # psql dbname < dbname_sql.dumpBackup and restore all databases (including users):
# pg_dumpall --clean > full.dump # psql -f full.dump postgresIn this case the restore is started with the database postgres which is better when reloading an empty cluster.
# /etc/init.d/mysql stop
or
# killall mysqld
# mysqld --skip-grant-tables
# mysqladmin -u root password 'newpasswd'
# /etc/init.d/mysql start
# mysql -u root mysql mysql> UPDATE USER SET PASSWORD=PASSWORD("newpassword") where user='root'; mysql> FLUSH PRIVILEGES; # Use username instead of "root" mysql> quit
# 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;
/etc/my.cnf contains the IP address to bind to. Typically comment the line bind-address = out.
# mysql -u root mysql mysql> GRANT ALL ON bobdb.* TO bob@'xxx.xxx.xxx.xxx' IDENTIFIED BY 'PASSWORD'; mysql> REVOKE GRANT OPTION ON foo.* FROM bar@'xxx.xxx.xxx.xxx'; mysql> FLUSH PRIVILEGES; # Use 'hostname' or also '%' for full access
# mysqldump -u root -psecret --add-drop-database dbname > dbname_sql.dump # mysql -u root -psecret -D dbname < dbname_sql.dumpBackup and restore all databases:
# mysqldump -u root -psecret --add-drop-database --all-databases > full.dump # mysql -u root -psecret < full.dumpHere 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.
sqlite3 for a 3.x database.
# sqlite database.db .dump > dump.sql # dump # sqlite database.db < dump.sql # restore
sqlite database_v2.db .dump | sqlite3 database_v3.db
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 /homeCheck that the quota is active with:
quota -v
options QUOTAAs 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
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
Disk quotas for user colin (uid 1007): Filesystem blocks soft hard inodes soft hard /dev/sda8 108 1000 2000 1 0 0
Quotas for user colin: /home: kbytes in use: 504184, limits (soft = 700000, hard = 800000) inodes in use: 1792, limits (soft = 0, hard = 0)
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
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
grep Pattern matchingsed Search and Replace strings or characterscut Print specific columns from a markersort Sort alphabetically or numericallyuniq Remove duplicate lines from a file# 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 -k4,4nThe first character in the sed pattern is a tab. To write a tab on the console, use ctrl-v ctrl-tab.
# 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 cmd2Modify 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
# 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 cmd2The 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 ExGxFxdxCxDxDxBxBxExExThe emacs mode enables to use the emacs keys shortcuts to modify the command prompt line. This is extremely useful (not only for emacs users). The most used commands are:
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.
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 $@)
$$ # 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.
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 # $1 is first argument of the function } myfunction "txt"
MYHOME=/home/colin cat > testhome.sh << _EOF # All of this goes into the file testhome.sh if [ -d "$MYHOME" ] ; then echo $MYHOME exists else echo $MYHOME does not exist fi _EOF sh testhome.sh
#!/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
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)
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>/,/<\/p>/d' t.xhtml # Delete lines that start with <p> # and end with </p> sed '/ *#/d; /^ *$/d' # Remove comments and blank lines sed 's/[ \t]*$//' # Remove trailing spaces (use tab as \t) sed 's/^[ \t]*//;s/[ \t]*$//' # Remove leading and trailing spaces sed 's/[^*]/[&]/' # Enclose first char with [] top->[t]op sed = file | sed 'N;s/\n/\t/' > file.num # Number lines on a file
[\^$.|?*+() # special characters any other will match themselves \ # escapes special characters and treat as literal * # repeat the previous item zero or more times . # single character except line break characters .* # match zero or more characters ^ # match at the start of a line/string $ # match at the end of a line/string .$ # match a single character at the end of line/string ^ $ # match line with a single space [^A-Z] # match any line beginning with any char from A to Z
sort -t. -k1,1n -k2,2n -k3,3n -k4,4n # Sort IPv4 ip addresses echo 'Test' | tr '[:lower:]' '[:upper:]' # Case conversion echo foo.bar | cut -d . -f 1 # Returns foo PID=$(ps | grep script.sh | grep bin | awk '{print $1}') # PID of a running script PID=$(ps axww | grep [p]ing | awk '{print $1}') # PID of ping (w/o grep pid) IP=$(ifconfig $INTERFACE | sed '/.*inet addr:/!d;s///;s/ .*//') # Linux IP=$(ifconfig $INTERFACE | sed '/.*inet /!d;s///;s/ .*//') # FreeBSD if [ `diff file1 file2 | wc -l` != 0 ]; then [...] fi # File changed? cat /etc/master.passwd | grep -v root | grep -v \*: | awk -F":" \ # Create http passwd '{ printf("%s:%s\n", $1, $2) }' > /usr/local/etc/apache2/passwd testuser=$(cat /usr/local/etc/apache2/passwd | grep -v \ # Check user in passwd root | grep -v \*: | awk -F":" '{ printf("%s\n", $1) }' | grep ^user$) :(){ :|:& };: # bash fork bomb. Will kill your machine tail +2 file > file2 # remove the first line from fileI use this little trick to change the file extension for many files at once. For example from .cxx to .cpp. Test it first without the
| sh at the end. You can also do this with the command rename if installed. Or with bash builtins.
# ls *.cxx | awk -F. '{print "mv "$0" "$1".cpp"}' | sh
# ls *.c | sed "s/.*/cp & &.$(date "+%Y%m%d")/" | sh # e.g. copy *.c to *.c.20080401
# rename .cxx .cpp *.cxx # Rename all .cxx to cpp
# for i in *.cxx; do mv $i ${i%%.cxx}.cpp; done # with bash builtins
strcpy(newstr,str) /* copy str to newstr */ expr1 ? expr2 : expr3 /* if (expr1) expr2 else expr3 */ x = (y > z) ? y : z; /* if (y > z) x = y; else x = z; */ int a[]={0,1,2}; /* Initialized array (or a[3]={0,1,2}; */ int a[2][3]={{1,2,3},{4,5,6}}; /* Array of array of ints */ int i = 12345; /* Convert in i to char str */ char str[10]; sprintf(str, "%d", i);
#include <stdio.h> main() { int number=42; printf("The answer is %i\n", number); }Compile with:
# gcc simple.c -o simple # ./simple The answer is 42
*pointer // Object pointed to by pointer &obj // Address of object obj obj.x // Member x of class obj (object obj) pobj->x // Member x of class pointed to by pobj // (*pobj).x and pobj->x are the same
#ifndef IPV4_H #define IPV4_H #include <string> namespace GenericUtils { // create a namespace class IPv4 { // class definition public: IPv4(); ~IPv4(); std::string IPint_to_IPquad(unsigned long ip);// member interface }; } //namespace GenericUtils #endif // IPV4_H
#include "IPv4.h" #include <string> #include <sstream> using namespace std; // use the namespaces using namespace GenericUtils; IPv4::IPv4() {} // default constructor/destructor IPv4::~IPv4() {} string IPv4::IPint_to_IPquad(unsigned long ip) { // member implementation ostringstream ipstr; // use a stringstream ipstr << ((ip &0xff000000) >> 24) // Bitwise right shift << "." << ((ip &0x00ff0000) >> 16) << "." << ((ip &0x0000ff00) >> 8) << "." << ((ip &0x000000ff)); return ipstr.str(); }
#include "IPv4.h" #include <iostream> #include <string> using namespace std; int main (int argc, char* argv[]) { string ipstr; // define variables unsigned long ipint = 1347861486; // The IP in integer form GenericUtils::IPv4 iputils; // create an object of the class ipstr = iputils.IPint_to_IPquad(ipint); // call the class member cout << ipint << " = " << ipstr << endl; // print the result return 0; }Compile and execute with:
# g++ -c IPv4.cpp simplecpp.cpp # Compile in objects # g++ IPv4.o simplecpp.o -o simplecpp.exe # Link the objects to final executable # ./simplecpp.exe 1347861486 = 80.86.187.238Use
ldd to check which libraries are used by the executable and where they are located. Also used to check if a shared library is missing or if the executable is static.
# ldd /sbin/ifconfig # list dynamic object dependencies # ar rcs staticlib.a *.o # create static archive # ar t staticlib.a # print the objects list from the archive # ar x /usr/lib/libc.a version.o # extract an object file from the archive # nm version.o # show function members provided by object
CC = g++ CFLAGS = -O OBJS = IPv4.o simplecpp.o simplecpp: ${OBJS} ${CC} -o simplecpp ${CFLAGS} ${OBJS} clean: rm -f ${TARGET} ${OBJS}
| Linux Documentation | en.tldp.org |
| Linux Man Pages | www.linuxmanpages.com |
| Linux commands directory | www.oreillynet.com/linux/cmd |
| Linux doc man howtos | linux.die.net |
| FreeBSD Handbook | www.freebsd.org/handbook |
| FreeBSD Man Pages | www.freebsd.org/cgi/man.cgi |
| FreeBSD user wiki | www.freebsdwiki.net |
| Solaris Man Pages | docs.sun.com/app/docs/coll/40.10 |
| Rosetta Stone for Unix | bhami.com/rosetta.html (a Unix command translator) |
| Unix guide cross reference | unixguide.net/unixguide.shtml |
| Linux commands line list | www.linuxcmd.org |
| Short Linux reference | www.pixelbeat.org/cmdline.html |
| Little command line goodies | www.shell-fu.org |
That's all folks!