All commands in alphabetical order

!! = Run the previous command
!?CF? = Run previous command containing the CF string
!129 *doc = Append *doc to command 129 from history
!99 = Run command number 99 from history
!ls = Run the previous ls command
!ls:s/CF/l = Run previous ls command, replacing CF with l
ls -la = Display files/directories beginning with dot (.)
ps auwx | mail -s ‘Process List’ james@sitename.com = A list of currently running processes is sent to the same user with subject of ‘Process List’.
sudo exportfs -rv = Verbose reload of exported shares
/etc/init.d/ntp = Show usage statement (with no options)
> /tmp/newfile2.txt = Create a blank file
alsamixer = Show alsamixer screen with playback view
alsamixer -c 1 = Use alsamixer on second (1) sound card
alsamixer -V all = Show with playback and capture views
alsamixer -V playback = Show only playback channels (default)
apropos umount = Search the man page descriptions for instances of a keyword
apt-cache depends = Print dependencies for a package (whether it’s installed or not).
apt-cache depends picasa = Shows dependencies for Picasa
apt-cache pkgnames = List all packages installed on the system.
apt-cache search = Case-insensitive search of the package database for the keyword given. The package names and descriptions are returned where that keyword is found.
apt-cache search picasa = Search for a package called Picasa
apt-cache search umount = Search the cached list of packages that may contain a command or description of umount.
apt-cache show Display information about the software from the named package.
apt-cache show picasa = Show information on Picasa
apt-cache stats = Print statistics on all packages installed.
apt-cache stats = Total numer of packages available
apt-config -V = Print version information of installed APT utilities.
aptitude help = Lists help for aptitude usage.
aptitude search = Lists packages matching the given keyword.
aptitude show = Lists information about the given package, installed or not.
arp -v = List ARP cache entries by name
arp -vn = List ARP cache entries by IP address
arping 10.0.0.23 = Query subnet to see if 10.0.0.23 is in use
arping -c 2 10.0.0.51 = Query 10.0.0.50 and stop after 2 counts
arping -f 10.0.0.50 = Query 10.0.0.50 and stop at the first reply
at 08/22/08 = Start a command at current time on August 22, 2008
at now +3 min = Start command running in three minutes
at now +7 days = Start a command in 7 days
at teatime = Start command at 4pm today
atq = Display que of at jobs
atrm 15 = Delete at job number 15
aumix = With no options, aumix runs screen-oriented
aumix -l q -m q = List current settings for line and mic only
aumix -m 70 -m R -m q = Set mic to 70%, set it to record, list mic
aumix -q = Show left/right volume and type for all channels
aumix -v 80 -m 0 = Set volume to 70% and microphone to 0
cal = Show current month's calendar
cal 2011 = Show whole year’s calendar
cal -j = Show Julian calendar (numbered from January 1)
cat /bin/ls | strings = List all ASCII text in ls
cat /proc/cpuinfo = View CPU details
cat -b myfile.txt = Show line numbers only on non-blank lines
cat md5sum.txt | grep Release.gpg |md5sum -c = Verify one particular file listed in md5sum.txt file
cat mp3list | mpg321 -@ - = Pipe playlist to mpg321
cat myfile.txt | head = View top of a file
cat myfile.txt | less = Page through the contents of a file
cat myfile.txt | sed s/john/john/ = Replace only the first occurrence of john in each line with john
cat myfile.txt = Send entire file to the screen
cat myfile.txt > copy.txt = Direct file contents to another file
cat myfile.txt >> myotherfile.txt = Append file contents to another file
cat -n myfile.txt = Show line numbers with output
cat -s myfile.txt = Display consecutive blank lines as one
cd - = Change to previous working directory
cd $HOME = Change to your home directory
cd $OLDPWD = Change to previous working directory
cd .. Change to parent of current directory
cd /home/ch = File completion: Completes to /home/john directory
cd /usr/bin = Change to usr/bin from root directory
cd ~ = Change to your home directory
cd ~/public_html = Change to public_html in your home directory
cd ~john = Change to john’ home directory
cd ~jo = User homedir completion: Completes to /home/john
cd = Change to your home directory
cd usr/bin = Change to usr/bin beneath current directory
cdparanoia -- “1:[40]-” = Rip tracks 1 from 40 secs in to end of the CD
cdparanoia -- “33-83” abc.wav = Rip tracks 33-83 to one file (abc.wav)
cdparanoia -a -- “52” = Rip track 52 and save to AIFC format
cdparanoia -B -- “54-74” = Rip tracks 54-74 into separate files
cdparanoia -B = Rip tracks as WAV files by track name
cdparanoia -f -- “34” = Rip track 34 and save to AIFF format
cdparanoia -vsQ = Checking CD drive for SCSI, MMC, CDDA support for copying files from CD to hard drive
cdparanoia -w -- “11” my.wav = Rip track 11 and name it my.wav
chgrp market test/ = Change group to market
chown john test/ = Change owner to john
chown john:market test/ = Change owner to john and group to market
chown -R john test/= Change all files below test/ to owner john
chsh -s /bin/sh = Change current user’s shell to /bin/sh
convert -charcoal 5 house.jpg char-house.png = Colorise image file
convert -colorize 175 house.jpg color-house.png = Colorise image file
convert icon.gif icon.bmp = Convert a GIF to a BMP file
convert photo.tiff photo.pcx = Convert a TIFF to a PCX file
convert -resize 1024x768 hat.jpg hat-sm.jpg = Convert image file
convert -rotate 220 sky.jpg sky-final.jpg = Rotate image 220 degrees
convert -rotate 15 house.jpg house-final.jpg = Rotate image 15 degrees
convert -sample 50%x50% dog.jpg dog-half.jpg = Convert image file
convert -sepia-tone 75% house.jpg oldhouse.png = Colorise image file
convert -swirl 300 photo.pcx weird.pcx = Swirl image file
convert -thumbnail 120x120 a.jpg a-a.png = Create a thumbnail
convert -thumbnail 120x120 -border 8 a.jpg a-b.png = Create thumbnail with a border
convert -thumbnail 120x120 -border 8 -rotate 8 a.jpg a-c.png = Create and rotate thumbnal with border
convert space.jpg space.png = Convert a JPEG to a PNG file
crontab -e = Create a personal crontab file
crontab -eu john = Edit another user’s crontab (root only)
crontab -l = List contents of your crontab file
crontab -r = Delete your crontab file
date ‘+%A %B %d %G’ = Display day, month, day of month, year
date ‘+The date today is %F.’ = Add words to the date output
date = Display current date, time and time zone
date --date=’3 May’ +%A = Display day on which May 4 falls Wednesday
date --date=’6 weeks’ = Display date 6 weeks from today
date --date=’7 months 8 days’ = Display date 7 months 8 days from today
debsums = This command will check every file on the system against the stock md5sum files.
df -h = Display space on file systems in human-readable form
df -hi = Add inode info
df -hl = Display space for local file systems only
df -hT = Display file system type with space
diff file1.txt file2.txt = Show difference between two files
dig +short www.yahoo.com = Display only name/IP address pair
dig +trace www.yahoo.com = Recursively trace DNS servers
dig yahoo.com mx = Queries for the mail exchanger
dig yahoo.com ns = Queries for the authoritative name servers
dig www.yahoo.com @4.2.2.1 = Query DNS server at 4.2.2.1
dig -x 66.113.99.70 = Get DNS information based on IP address
disown %3 = Disconnect job %3 from current shell
disown -a = Disconnect all jobs from current shell
disown -h = Protect all jobs from HUP sent to current shell
dmesg | grep “[ ]ata\|^ata” = Show ata kernel device information
dpkg -L initscripts = List all the files contained in the initscripts package
dpkg-query -S umount = Search the list of installed packages for the filename umount, revealing the package it is in.
dstat -t -c 3 = View CPU usage continuously with time stamps
du -h /home/ = Show disk space usage for /home directory
du -sh /home/john = Display disk use for another user as root
echo $HISTFILE $HISTSIZE $HISTFILESIZE =
echo $PA = Env variable completion: Completes to $PATH
echo $PATH = Show the current PATH
echo john | tr ‘[:lower:]’ ‘[:upper:]’ = Translate john into john
echo john | tr a-z A-Z = Translate john into john
elinks www.yahoo.com = Opens file name or URL you request
ethtool -h | less = View options to the ethtool command
fc = Edit the previous command, then run it
fc 999 = Edit command number 999, then run it
fc -e /usr/bin/nano 999 = Use nano to edit command 999
find / ! -group root -type f -print 2> /dev/null | xargs ls -l = Find files that are not owned by group root, exclamation mark means not
find /home/john/ -atime +66 = Find files that have not been accessed in /home/john for more 66 days
find /sbin/ -perm 750 -print = Find files is sbin directory with permission 750
find /sbin/ -type f ! -perm /o+w -print | xargs ls -l = Find files that are not writable by others
find /usr -name umount = Search the /usr file system for a filename or directory named umount.
find /var -user john -exec ls -l {} \;= Find files owned by user john in var directory and executes ls -l commandon it
find /var -user john -print | xargs ls -l = Find files owned by user john in var directory and executes ls -l commandon it
finger -l john = User information (long)
finger -s john = User information (short)
flac -8 top.wav -o top.flac = Raises compression level to 8
flac now.aiff -o now2.flac = Encodes AIFF to FLAC (now.flac)
flac now.wav = Encodes WAV to FLAC (now.flac)
free = List memory usage in kilobytes (-k default)
free -b = List memory usage in blocks
free -g = List memory usage in gigabytes
free -m = List memory usage in megabytes
free -mt = List memory usage with totals displayed (Swap + Mem)
free -s 5 = Continuously display memory usage every 5 seconds
from the /etc/passwd file
fuser /boot = Show parent PIDs for processes opening /boot
fuser -l = List supported signals
fuser -m /boot = Show all PIDs for processes opening /boot
fuser -mauv /boot = Verbose output of processes with /boot open
fuser -u /boot = Show PIDs/user for this shell open in /boot
gnome-terminal --geometry 90x33 = Start terminal 90 characters by 33 lines
gnome-terminal --tab --tab --tab = Start a terminal with three open tabs
gnome-terminal -x alsamixer = Start terminal with alsamixer displayed
gnome-terminal --zoom=2 = Start terminal with larger font
grep 192.123.13.1 /var/log/httpd/access-log | wc -l = Lists how many entries in Apache log come from a specific IP address/webpage
grep 404 /var/log/httpd/access_log = Show lines containing 404
grep --color -Rn VirtualHost /etc/httpd/conf* = Colorise the term VirtualHost
grep john myfile.txt = Show lines containing john
grep -i selinux /var/log/messages = Search file for the term selinux not case sensitive
grep -R VirtualHost /etc/httpd/conf* = Search for the term VirtualHost in /etc/httpd/conf and /etc/httpd/conf.d directories
grep -Rl VirtualHost /etc/httpd/conf* = Display only the names of the files that contain the term VirtualHost
grep -Rn VirtualHost /etc/httpd/conf* = Locate line numbers where the term VirtualHost occurs
grep -v “ 400 “ /var/log/httpd/access_log* = Show lines without “ 420 “
groups john = List the groups that a user belongs to
head -15 myfile.txt = Show the first 15 lines of a file
head myfile.txt = View top of a file
head -n 15 myfile.txt = Show the first 15 lines of a file
history 15 = List last 15 commands in history
host 13.173.93.70 = Reverse DNS lookup
hostname = View the local computer’s full DNS host name
hwclock -r = Display current hardware clock settings
hwclock --systohc = Reset hardware clock from system clock
identify home.jpg = Information about image
identify -verbose home.jpg | less = Information about image
ifconfig = Check network interface status
ifconfig -a = Show all connections
ifconfig eth0 = Display the address information and status of eth0 Ethernet interface
info ls = The previous command shows information on the ls command
iostat -c 30 = Display CPU stats every 30 seconds
iostat -c -t = Print time stamp with CPU report
iostat -c -t 20 10 = Repeat every 20 seconds for 10 times
ip addr help = View help for the addr object
ip addr show eth0 = Info about etho NIC
ip help = View ip usage statement
ip r = Display basic routing
ip route = Check defualt gateway
ip route = Display basic routing
ip route help = View help for the route object
ip route show = Display basic routing information
ip tunnel help = View help for the tunnel object
ipcalc -bmn 192.55.16.100/27 = calculate a host computer’s netmask from its CIDR IP address
iwconfig = Search for wireless cards
jobs = Display background jobs for current shell
jobs -l %2 = Display information only for job %2
jobs -l = Display PID with each job’s information
kill %3 = Kill the process represented by job %3
kill 888 = Send SIGTERM to process with PID 888
kill -9 444 = Send SIGKILL to process with PID 444
kill -SIGCONT 555 = Continue a stopped process (pid 555)
killall -SIGHUP sendmail = Have sendmail processes reread config files
killall spamd = Kill all spamd daemons currently running
last = List the most recent successful logins
less file.txt = Page through a text file
lftp john@site.com = Authenticated connection
lftp mirrors.kernel.org = Anonymous connection
lftp Start = lftp with no connection
lftp -u john example.com = Authenticated connection
lftp -u john,Mypwd example.com = Authentication with password
ln myfile myfile-hardlink = Create hard link
ln -s myfile myfile-symlink = Create symbolic link
locate mount = Use the locate command to search its list of (configurable) directories for mount
ls | tr ‘\n’ ‘ ‘ = Replace newline characters with spaces
ls | tr -d ‘\n’ = Delete new lines (resulting in one line)
ls -C = Show files listing in columns
ls --color = always = Show file types as different colors
ls -F = Add a character to indicate file type
ls -l Files and directories in current directory
ls -lh = List file sizes in human-readable form (K, M, etc.)
ls -li = Lists the inode associated with each file
ls -ln = List numeric user/group IDs, instead of names
ls -lR = List files recursively, from current directory and subdirectories
ls -lS = Orders files by size
ls -lt = Orders files by time recently changed
ls -lu = Orders files by time recently accessed
lsmod = Display all loaded modules
lsof /mnt/sda1 = List anything open on /mnt/sda1 file system
lsof | less = List processes holding files and directories open
lsof +d /mnt/sda1/dx = List anything open under /mnt/sda1/dx directory
lsof -c bash = List files open by bash shells
lsof -d cwd = List directories open as current working directory
lsof -u john = List files and directories open by user john
lspci | grep -i wireless = Search for wireless PCI cards
lspci = List PCI hardware items
lspci -v = List PCI hardware items with more details
lspci -vv List PCI hardware items with even more details
mail -s ‘My Linux version’ john@example.com < /etc/lsb-release = Sends the contents of the /etc/lsb-release file to the user john@example.com. The subject (-s) is set to ‘My Linux Version’.
man 5 crontab = Shows the section 5 man page for crontab
man 8 umount = View section 8 of the man page for umount
man –a crontab = Shows all man page sections, in succession, for crontab
man crontab –P more = Uses the pager program more for paging through the crontab man page
man –f crontab = Equivalent to the whatis command
man –k crontab = Equivalent to the apropos command
md5sum -c md5sum.txt = Verify all the files listed in the current directory and listed in md5sum.txt file contained in the current directory
md5sum whatever.iso = Verify file
message and attaches the file /etc/lsb-release
method for updating a system.
minicom -s = Create your modem settings
mkdir /tmp/new = Create “new” directory in /tmp
mkdir -m 700 /tmp/new2 = Create new2 with drwx — — — permissions
mkdir -p /tmp/a/b/c/new = Create parent directories as needed for “new”
modinfo snd_ens1371 = Info about partcular module
modprobe -l | grep c-qcam = List all modules, then look for c-qcam
more myfile.txt = Page through the contents of a file
mount = List mounted file systems remote and local
mount -t ext2 = List mounted ext2 file systems
mount -t ext2 -l = List mounted ext2 file systems with labels
mpg321 -@ mp3list = Play songs from playlist of MP3s
mpg321 yoursong.mp3 = Play MP3 file
mpg321 -z *.mp3 = Play files in pseudo-random order
mpg321 -Z *.mp3 = Same as -z, but repeat forever
mutt -s “My Linux Version” -a /etc/lsb-release \john@example.com < email-body.txt = Sends the file email-body.txt as the body of the
mutt= Begin mutt session
netstat -i = Get network interface statistics for eth0
netstat -ic = Refresh network statistics every second
netstat -s | less = Show summary of TCP, ICMP, UDP activities
nice = Run nice to determine current niceness
nice -n 12 nroff -man a.roff | less = Format man pages at low priority
nohup nice -9 gcc hello.c & = Run gcc uninterrupted and higher priority
nohup updatedb & = Run updatedb with no ability to interrupt
ogg123 /usr/share/example-content/ubuntu\ Sax.ogg = Play example file
ogg123 /var/music/ = Play songs in /var/music and sub dirs
ogg123 -@ myplaylist = Play songs from playlist
ogg123 http://vorbis.com/music/Lumme-Badloop.ogg = Play web address
ogg123 mysong.ogg = Play ogg file
ogg123 -z *.ogg = Play files in pseudo-random order
oggenc ab.flac -o new.ogg = Encodes FLAC to Ogg (new.ogg)
oggenc ab.wav = Encodes WAV to Ogg (ab.ogg)
oggenc ab.wav -q 9 = Raises encoding quality to 9
pgrep init = Show PID for any process including ‘init’ string
pgrep -l init = Show PID and name for any process including ‘init’ string
pgrep -lu john = List all processes owned by user john
ping = Host completion: Show hosts from /etc/hosts
ping 10.0.0.1 = Check availabiity of ip address
ping -a 10.0.0.1 = Add an audible ping as ping progresses
ping -c 4 10.0.0.1 = Ping 4 times and exit (default in Windows)
ping -i 3 10.0.0.1 = Send packets in 3-second intervals
ping -q -c 5 10.0.0.1 =Show summary of pings (works best with -c)
ping -s 1500 10.0.0.1 = Set packet size to 1500 bytes
play *.wav = Play all WAV files in directory (up to 32)
play hi.au vol .6 = AU file, lower volume (can lower distortion)
play inconceivable.wav = Play WAV file (may be ripped from CD)
play -r 14000 short.aiff = AIFF, sampling rate of 14000 hertz
ps = List all processes running
ps auwwx = Show every running process, long BSD style, unlimited width
ps auwx | grep “\[*\]” = Show bracketed commands
ps auwx | grep init = Show init lines from ps output
ps auwx | head -15 = Show the first 15 lines of ps output
ps auwx | head n -15 = Show the first 15 lines of ps output
ps auwx | less = Page through the output of ps
ps auwx | more = Page through the output of ps (press spacebar)
ps auwx | tail -n 15 = Display the last 15 lines of ps output
ps auwx = Show every running process, long BSD style, wide format
ps aux = Show every running process, long BSD style
ps ax = Show every running process, short BSD style
ps axjf = Show process hierarchy in BSD-style output
ps -C httpd = Display running httpd processes
ps -e = Show every running process
ps -eF = Show every running process, extra full-format listing
ps -ef = Show every running process, full-format listing
ps -ef --forest = Show process hierarchy in forest format
ps -ejH = Show process hierarchy with process/session IDs
ps -el = Show every running process, long listing
ps -eo ppid,user,%mem,size,vsize,comm --sort=-size = Sort by mem use
ps -eo ppid,user,bsdstart,bsdtime,%cpu,args --sort=-%cpu = Sort by CPU use
ps -eo ppid,user,nice,cputime,args --sort=-nice = Sort by low priority
ps -eo ppid,user,stat,tname,sess,cputime,args --sort=user = Sort by user
ps -fp $(pgrep nautilus) = Search for nautilus and run ps (full)
ps -fu john = Show all processes run by user john with process ID
ps -Fu john = Show all processes run by user john with SZ and PSR
ps -p `pgrep metacity`= Search for metacity and run ps (short)
ps -p 5413 -o pid,ppid,bsdtime,args = Display info for PID 5413
ps -u john = Show all processes run by user john
ps -u john u = Show all processes run by user john with cpu and memory usage
ps -U john,john -o pid,ruser,tty,stat,args = See info for 2 users
pstree = Show processes alphabetically in tree format
pwd = Print current working directory
renice +2 -u john = Renice john’ processes +2
renice +5 433 = Renice PID 433 by +5
route = Display local routing table information
route -n = Display routing table without DNS lookup
runlevel = Display current and previous run levels
scp myfile john@server1:/tmp/= Copy myfile to server1
scp -P 1333 myfile server1:/tmp/ = Connect to a particular port
scp -p myfile server1:/tmp/ = Preserve permissions and timestamps on the copied files
scp -r mydir john@server1:/tmp/ = Copies all mydir to remote /tmp
scp server1:/tmp/myfile . = Copy remote myfile to local working dir
sdo apt-get remove packagename = Uninstall package
sed ‘s/\/home\/bob/\/home2\/bob/g’ < /etc/passwd = Replaces the first occurrences of the text /home/bob to /home2/bob
sed ‘s-/home/bob/-/home2/bob/-’ < /etc/passwd = Replaces the first occurrences of the text /home/bob to /home2/bob
sed ‘sD/home/bob/D/home2/bob/D’ < /etc/passwd = Replaces the first occurrences of the text /home/bob to /home2/bob
sed -e s/john/john/g -e s/john/john/g < myfile.txt = All occurrences of john are changed to john and occurrences of john are changed to john
sed s/3/TREE/ < f1.txt > f2.txt = Change 4 to FOUR and send to f2.txt
sed s/john/john/g < myfile.txt > mynewfile.txt = Replace all occurrences of john in file with john and redirect the output to file mynewfile.txt
seq 1 7 > f1.txt = Send a sequence of numbers to f1.txt
setserial -a /dev/ttyS0 = View serial port details
setserial -g /dev/ttyS0 /dev/ttyS1 /dev/ttyS2 /dev/ttyS3 = See port info
setserial -ga /dev/ttyS0 /dev/ttyS1 = Check multiple port details
sha1sum whatever.iso = Verify file
slabtop = Display kernel slab memory cache information in a screen-oriented view
sox head.wav tail.wav output.wav = Concatenat two files into one single output file
sox now.wav now.aiff = Encodes WAV to AIFF (now.aiff)
sox sound1.wav output.wav trim 1 9 = Keep from 1-9 seconds of file
sox sound1.wav output.wav trim 34 = Trim 34 seconds from start
soxmix head.wav tail.wav output.wav = Mix two files into one single file
strings /bin/ls | grep -i libc = Find occurrences of libc in ls
strings /bin/ls = List all ASCII text in ls
stty -F /dev/ttyS0 -a = View tty settings for serial port
sudo /etc/init.d/networking restart = Shutdown and bring up network interfaces
sudo /etc/init.d/nfs-kernel-server reload = Reload exported shared directories
sudo /etc/init.d/ntp force-reload = Reload settings in config file
sudo /etc/init.d/ntp restart = Restart NTP service (first off, then on)
sudo /etc/init.d/ntp start = Start Samba service immediately
sudo /etc/init.d/ntp status = Check if the NTP service is running (smbd)
sudo /etc/init.d/ntp stop = Stop NTP service
sudo /etc/init.d/ntp try-restart = Restart NTP service (if already running)
sudo /usr/sbin/exportfs -v = Show all shared directories
sudo apt-get autoclean = Can be run anytime to delete partially downloaded packages, or packages no longer installed.
sudo apt-get clean = Removes all cached packages from /var/cache/apt/archives to free up disk space.
sudo apt-get -d install = Download the package only, placing it in /var/cache/apt/archives.
sudo apt-get dist-upgrade = Updates the entire system to a new release, even if it means removing packages. Note: This is not the preferred
sudo apt-get -f install = Do a sanity check for broken packages. This tries to fix any “unmet dependency” messages.
sudo apt-get install = Download and install the given package name as found in the package database. Starting with APT version 0.6, this command will automatically verify package authenticity for gpg keys it knows about (http://wiki.debian.org/SecureApt).
sudo apt-get install packagename = Install package you want
sudo apt-get --purge remove = Remove the named package and all its configuration files. Remove the --purge keyword to keep config files.
sudo apt-get update = Consults /etc/apt/sources.list and updates the database of available packages. Be sure to run this command
sudo apt-get update = Refresh the list of cached packages
sudo apt-get update packagename = Update to new version of the package
sudo apt-get upgrade = Check updates for all installed packages and then prompt to download and install them.
sudo apt-get upgrade pakagename = Upgrade before updating a package
sudo aptitude = Starts the curses interface. Use Ctrl+t to access the menu and the q key to quit.
sudo aptitude autoclean = Removes all outdated .deb files from the /var/cache/apt/archives directory. This maintains a current cache without filling up the disk.
sudo aptitude clean = Removes all downloaded .deb files from the /var/cache/apt/archives directory.
sudo aptitude dist-upgrade = Upgrades all packages to their most recent versions, removing or installing packages as necessary. The upgrade option is advised over dist-upgrade.
sudo aptitude download = Downloads the given package, but does not install it.
sudo aptitude install = Installs the given package to the system. Note: There are several options for selecting specific versions and using wildcards.
sudo aptitude remove = Removes the given package from the system.
sudo aptitude update = Updates the available package indexes from the APT sources.
sudo aptitude upgrade = Upgrades all packages in use to their latest versions.
sudo apt-key list = List gpg keys that APT knows about.
sudo arp -d 10.0.0.50 = Delete address 10.0.0.50 from ARP cache
sudo arp -s 10.0.0.51 00:0B:6A:02:EC:95 = Add IP and MAC addresses to ARP
sudo arping -I eth0 10.0.0.50 = Specify interface to query from
sudo badblocks /dev/sda1 = Physically scan hard disk for bad blocks
sudo badblocks -v /dev/sda1 = Add verbosity to hard disk scan
sudo badblocks -vsn /dev/sda1 = Check bad blocks, non-destructive
sudo badblocks -vsw /dev/sda1 = Check bad blocks, destructive, could erase all data on a partition
sudo cat /var/log/messages* | less = Page through /var/log/messages
sudo chage -d 5 perry = Force user’s password to expire in 5 days
sudo chage -I 40 frank = Make account inactive in 40 days
sudo chage -l vern = View password expiration information
sudo chmod -R 000 /tmp/test = Close all permissions below /tmp/test
sudo chmod -R 700 /tmp/test = Open permission only to owner below /tmp/test
sudo chmod -R a+rwx /tmp/test = Open all permissions to all below /tmp/test
sudo chsh -s /bin/sh john = Change a user’s shell to /bin/sh
sudo cp /usr/share/zoneinfo/America/Chicago /etc/localtime = Change current time zone to that of America/Chicago
sudo date 081215212008 = Set date/time to Aug. 12, 2:21PM, 2008
sudo date --set=’+7 minutes’ = Set time to 7 minutes later
sudo date --set=’-1 month’ = Set date/time to one month earlier
sudo dd if=/dev/hda1 of=/dev/hdb2 = Clones the first partition of the primary master IDE drive to the second partition of the primary slave IDE drive
sudo dmidecode | less = List hardware components
sudo du -h --max-depth=1 /home = Display disk space one level below /home
sudo du -h --max-depth=1 /home = Display disk space two levels below /home
sudo du -sch /home /var = Show multiple directory and total summaries
sudo du -sh --exclude=’*.iso’ /home/john = Exclude ISO images from disk space
sudo e2label /dev/sda2 = Dispay lable of partition
sudo e2label /dev/sda2 mypartition = Change label of partition
sudo eject /dev/cdrom = Unmount and eject a CD
sudo ethtool eth0 = See settings for NIC at eth0
sudo ethtool -i eth0 = Display driver information for NIC
sudo ethtool -S eth0 = Show statistics for NIC at eth0
sudo ethtool -s eth0 speed 10 duplex half autoneg off = Turn off auto-negotiation and hard-set the speed to 10 Mpbs, half-duplex
sudo exportfs -r = Reload exported shared directories
sudo fdisk /dev/sda = Start interactive fdisk session with disk 1
sudo fdisk -l /dev/sdb = List disk partitions for a specific disk
sudo fdisk -l = List disk partitions for every disk
sudo fuser -k /boot = Kill all processes with /boot files open (SIGKILL)
sudo groupadd -g 1701 sales = Create new group with GID of 1701
sudo groupadd marketing = Create new group with next available GID
sudo groupadd -o -g 74 mysshd = Create group with existing GID
sudo groupdel myad = Remove existing myad group
sudo groupmod -g 491 myadmin = Modify myadmin to use GID 491
sudo groupmod -n myad myadmin = Change name of myadmin group to myad
sudo halt -h = Put hard drives in standby mode before halting
sudo halt -n = Don’t run sync to sync hard drives before shutdown
sudo hdparm /dev/hda = Display hard disk settings (IDE drive)
sudo hdparm /dev/sda = Display hard disk settings (SATA or SCSI drive)
sudo hdparm –I /dev/sda = Display detailed drive information
sudo hwclock --adjust = Adjust hardware clock time for drift
sudo hwclock --hctosys = Reset system clock from hardware clock
sudo hwclock --set --date=”3/18/08 18:22:00” = Set clock to new date/time
sudo ifdown eth0 = Take the eth0 network interface offline
sudo ifup eth0 = Bring the eth0 network interface on
sudo init 5 = Change the current run level to 5 (X Desktop)
sudo init q = Start or stop changed processes in inittab file
sudo ip r add 192.168.0.0/24 via 10.0.0.100 = Add route no interface
sudo ip r add 192.168.0.0/24 via 10.0.0.100 dev eth0 = Add route to interface
sudo ip r del 192.168.0.0/24 = Delete route
sudo iptables -F = Flush all iptables rules
sudo iptables -L = Current rules for firewall
sudo iptables -L --line-numbers = Show line number in chain for each rule
sudo iptables -n -L = Filter rules, IP numbers (no DNS lookup)
sudo iptables -nvL --line-numbers = Our tech editor’s favorite combination
sudo iptables -t nat -L = Display current iptables nat table
sudo iptables -v -L = Verbose output (with packet/byte counts)
sudo iwconfig wlan0 ap any = Use any access point available
sudo iwconfig wlan0 channel 3 = Set the channel to 3
sudo iwconfig wlan0 essid “MyWireless” = Set essid to MyWireless
sudo iwconfig wlan0 key 1234-5555-66 = Set encryption key to 1234-5555-66
sudo iwconfig wlan0 mode Ad-Hoc = Change from Managed to Ad-Hoc mode
sudo iwconfig wlan0 retry 20 = Set MAC retransmissions to 20
sudo iwconfig wlan0 sens -50 = Set sensitivity to –50
sudo lastb = List the most recent unsuccessful logins
sudo ln –s /usr/share/zoneinfo/America/Chicago /etc/localtime = Change current time zone to that of America/Chicago via symlink
sudo lsof | grep mymount = Find open files on mymount partition
sudo mii-tool -F 10baseT-FD eth0 = Force speed/duplex to 10baseT-FD
sudo mii-tool -r eth0 = Re-enable auto-negotiation for an old NIC
sudo mii-tool -v = Show verbose output of settings for old NIC
sudo mkfs -t ext3 /dev/sdb1 = Create ext3 file system on sba1
sudo mkfs -t ext3 -v -c /dev/sdb1 = More verbose and scan for bad blocks
sudo mkfs.ext3 -c /dev/sdb1 = Same result as previous command
sudo mkswap /dev/sda1 = Format sda1 as a swap partition
sudo mkswap -c /dev/sda1 = Check swap area for bad blocks
sudo modprobe c-qcam = Load module for Color QuickCam
sudo modprobe -r c-qcam = Remove module for Color QuickCam
sudo mount -t ext3 /dev/sda1 /mnt/mymount/= Mount a et3 type local file system on /mnt/mymount
sudo mount /dev/sda1 /mnt/mymount/ = Mount a local file system on /mnt/mymount
sudo mount -v --move /mnt/mymount/ /tmp/mydir/ = Move a file system from one point to another
sudo mount -v -t ext3 -o ro /dev/sda1 /mnt/mymount/= Mount read only
sudo mount -v -t ext3 -o rw /dev/sda1 /mnt/mymount/ Mount read/write = Mount write only
sudo netstat -tanp | grep -i listen = View daemons listening to a port
sudo netstat -tanp = View active TCP connections
sudo netstat -uanp = View active UDP connections
sudo nice -n -10 gimp = Launch gimp at higher priority
sudo nmap 10.0.0.1 = Scan ports on computer at 10.0.0.1
sudo nmap -vv 10.0.0.1 = Show maximum verbosity from nmap output
sudo nmap -vv -P0 -O -p 100-200 10.0.0.1 = No ping, OS fingerprint, ports 100-200
sudo nmap -vv –sP 10.0.0.0/24 = Scan hosts on an entire network
sudo passwd -i 14 vern = Days after expiration account is disabled
sudo passwd john = Add password for user john
sudo passwd -l john = Lock the user account (john)
sudo passwd -n 2 vern = Set minimum password life to 2 days
sudo passwd -u john = Unlock a locked user account (john)
sudo passwd -w 10 vern = Warn of password expiration 10 days in advance
sudo passwd -x 300 vern = Set maximum password life to 300 days
sudo ping -f 10.0.0.1 = Send a flood of pings (must be root)
sudo ping -I 10.0.0.155 10.0.0.1 = Set source to 10.0.0.155
sudo ping -I eth0 10.0.0.1 = Set source to eth0 (use if multiple NICs)
sudo reboot = Reboot the computer
sudo renice -3 `pgrep -u john spamd` = Renice john’ spamd processes –3
sudo route add default gw 10.0.0.2 = Add 10.0.0.2 as default gateway
sudo route add -net 192.168.0.0 netmask 255.255.255.0 eth0
sudo route add -net 192.168.0.0 netmask 255.255.255.0 gw 10.0.0.100
sudo route del -net 192.168.0.0 netmask 255.255.255.0 = Delete a route
sudo sfdisk /dev/sda < sda-table = Restore partition table from file
sudo sfdisk –d /dev/sda | sfdisk /dev/sdb = Copy partition table from disk to disk
sudo sfdisk –d /dev/sda > sda-table = Back up partition table to file
sudo shutdown 10 ‘Bye!’ = Send custom message to users before shutdown
sudo shutdown 10 = Shutdown in ten minutes after warning the users
sudo shutdown -r 10 = Reboot in ten minutes after warning the users
sudo swapoff -v /tmp/swapfile = swapoff on /tmp/swapfile
sudo swapon /dev/sda1 = Turn swap on for /dev/sda1 partition
sudo swapon -v /dev/sda1 = Increase verbosity as swap is turned on
sudo swapon -v /tmp/swapfile = Turn swap on for the /tmp/swapfile file
sudo swapon -v -p 1 /dev/sda1 = Assign top swap priority to sda1
sudo sysctl -a | less = List all kernel parameters
sudo sysctl kernel.hostname = List value of particular parameter
sudo sysctl -p = Load parms from /etc/sysctl.conf
sudo sysctl -w kernel.hostname=joe = Set value of kernel.hostname
sudo tail -f /var/log/messages = Watch cotents of a text file grow over time
sudo tcpdump | grep -v ssh = Find packets except those associated with ssh
sudo tune2fs -i 0 /dev/sda1 = Disable time-dependent checking
sudo tune2fs -i 12 /dev/sda1 = Check after 12 days
sudo tune2fs -i 11d /dev/sda1 = Check after 12 day
sudo tune2fs -i 9w /dev/sda1 = Check after 9 weeks
sudo tune2fs -i 3m /dev/sda1 = Check after 3 months
sudo umount -v /dev/sda1 = Unmount by device name
sudo umount -v /mnt/mymount/ = Unmount by mount point
sudo umount -vl /mnt/mymount/ = Perform a lazy unmount when te device is busy
sudo useradd billyq = Prevent creation of home directory, no -m
sudo useradd -c “John T. Watson” tlot = Add user’s full name to comment field
sudo useradd -D -b /home2 -s /bin/csh = Set default base dir and shell
sudo useradd -D -e 2020-01-01 = Set all new users to expire in 2020
sudo useradd -e 2020-08-01 jerry = Add account to expire August 01, 2020
sudo useradd -f 0 jdoe = Create a disabled account
sudo useradd -G support,sales timd = Add user to support and sales groups
sudo useradd -m -d /home/jj jones = Create /var/x/jj home directory
sudo useradd -m john = Add user named john
sudo useradd -s /bin/tcsh joeq = Assign a new default shell (tcsh); you must install this shell
sudo useradd -s /sbin/nologin billt = Keep user from shelling in
sudo useradd -u 1101 -g 1300 skolmes = Use specific UID and GID for user
sudo usermod -c “John Watts” tlot = Change user’s name in comment field
sudo usermod -L john = Lock the user account named john
sudo usermod -s /bin/sh joeq = Change default shell to sh
sudo usermod -U john = Unlock user account named john
sudo wvdial = Dial out and connect to your ISP
sudo wvdialconf /etc/wvdial.conf = Scan serial ports, create config file
sudo# renice -5 $(pgrep firefox) = Search for firefox, improve its priority
swapon -s = View all swap partitions that are on
tail -15 myfile.txt = Display the last 15 lines in a file
tail -f /var/log/httpd/access_log = Watch web server messages live
tail -f /var/log/maillog = Watch mail server messages live
tail -f /var/log/messages = Watch system messages live
tail -n 15 myfile.txt = Display the last 15 lines in a file
top = Display system uptime, tasks, CPU usage, and memory usage, followed by a list of running processes, sorted by CPU usage
top -b = Run in non-interative non-screen-oriented mode
top -d 50 = Change update delay to 50 seconds (from default 3)
top -n 5 = Refresh the screen 5 times before quitting
top -p 19,26 = Only display processes 19 and 26
top -u john = Only see processes of effective user name john
touch /tmp/newfilename.txt = Create a blank file
tr -d f < file.txt = Delete every letter f from the file
tr f F < file.txt = Replace every f in the file with F
tracepath boost.yahoo.com = Use UDP to trace the route
tracer = Command completion: Completes to traceroute command
traceroute boost.yahoo.com = Follow the route taken to a host
traceroute -I boost.yahoo.com = Use ICMP packets to trace a route
traceroute -n boost.yahoo.com = Disable name resolution in trace
traceroute -p 25 boost.yahoo.com = Connect to port 25 in trace
uname -a = Display all available kernel info
uname -r = Display name of kernel release
unix2dos < myunixfile.txt > mydosfile.txt = Convert Unix file into DOS file
useradd -D = List default settings for useradd
userdel jimbo = Delete user, not user’s home directory
userdel -r john = Delete user, home directory, and mail spool
users = List who is currently logged in (short form)
vmstat 6 = Display memory use over a given time period (6 seconds)
vmstat -d = Display disk read, write, and input/output statistics
vmstat -m | less = Page through kernel slab memory cache
vmstat -n 2 15 = Output every two seconds, repeat 15 times
vmstat -p sda1 = Display read/write stats for a disk partition
vmstat -s | less = Display event counters and memory statistics
vmstat -S k = Display output in 1000-byte kilobytes
vmstat -S K = Display output in 1024-byte kilobytes
vmstat -S m = Display output in 1000k megabytes
vmstat -S M = Display output in 1024k megabytes
vmstat -S M -s | less = Display statistics in megabytes
watch ‘cat /proc/loadavg’ = Watch output of command every seconds
watch ‘ls –l mydownload.iso’ = Watch size of iso file as it downloads
watch -d ‘ls -l’ = Watch difference between outputs of same command
watch -n 10 ‘ls -l’ = Watch output of command every 10 seconds
watch netstat -i = Refresh network statistics (screen oriented)
wc /var/log/*.log = Counts number of lines, words, bytes for all .log files in /var/log directory
wc /var/log/dmesg = Counts number of lines, words, bytes in file
wget -c http://example.com/DVD.iso = Resume download where stopped
wget -E http://www.aspexamples.com = Append .html to downloaded files
wget ftp://user:password@ftp.example.com/path/to/file
wget http://example.com/DVD.iso = Begin downloading large file in one session
wget http://www.wiley.com = Download only the Web page
wget https://help.ubuntu.com/7.04/common/img/headerlogo.png = Download file from a server which does not require username or password
wget -m http://www.linuxtoys.net = Mirror an entire website
wget -mEkK http://www.linuxtoys.net = Make local copy of website
wget -p http://www.wiley.com = Download Web page and other elements
wget -pk http://www.wiley.com = Download pages and use local file names
wget -pkK http://www.wiley.com = Rename to local names, keep original
wget --user=user --password=password ftp://ftp.example.com/path/to/file = Supply username and password
whenever sources.list is changed.
whereis mount = Show where the first binary and man page are for the mount command
which mount = Find the first occurrence of the mount command in the PATH
who -u = List who is currently logged in (long form)