Linux command line reference for common operations.

Command Description
  apropos whatis Show commands pertinent to string. See also threadsafe
  man -t ascii | ps2pdf – > ascii.pdf make a pdf of a manual page
  which command Show full path name of command
  time command See how long a command takes
  time cat Start stopwatch. Ctrl-d to stop. See also sw
dir navigation
  cd – Go to previous directory
  cd Go to $HOME directory
  (cd dir && command) Go to dir, execute command and return to current dir
  pushd . Put current dir on stack so you can popd back to it
  alias l=’ls -l –color=auto’ quick dir listing. See also l
  ls -lrt List files by date. See also newest and find_mm_yyyy
  ls /usr/bin | pr -T9 -W$COLUMNS Print in 9 columns to width of terminal
  find -name ‘*.[ch]’ | xargs grep -E ‘expr’ Search ‘expr’ in this dir and below. See also findrepo
  find -type f -print0 | xargs -r0 grep -F ‘example’ Search all regular files for ‘example’ in this dir and below
  find -maxdepth 1 -type f | xargs grep -F ‘example’ Search all regular files for ‘example’ in this dir
  find -maxdepth 1 -type d | while read dir; do echo $dir; echo cmd2; done Process each item with multiple commands (in while loop)
  find -type f ! -perm -444 Find files not readable by all (useful for web site)
  find -type d ! -perm -111 Find dirs not accessible by all (useful for web site)
  locate -r ‘file[^/]*\.txt’ Search cached index for names. This re is like glob *file*.txt
  look reference Quickly search (sorted) dictionary for prefix
  grep –color reference /usr/share/dict/words Highlight occurances of regular expression in dictionary
archives and compression
  gpg -c file Encrypt file
  gpg file.gpg Decrypt file
  tar -c dir/ | bzip2 > dir.tar.bz2 Make compressed archive of dir/
  bzip2 -dc dir.tar.bz2 | tar -x Extract archive (use gzip instead of bzip2 for tar.gz files)
  tar -c dir/ | gzip | gpg -c | ssh user@remote ‘dd of=dir.tar.gz.gpg’ Make encrypted archive of dir/ on remote machine
  find dir/ -name ‘*.txt’ | tar -c –files-from=- | bzip2 > dir_txt.tar.bz2 Make archive of subset of dir/ and below
  find dir/ -name ‘*.txt’ | xargs cp -a –target-directory=dir_txt/ –parents Make copy of subset of dir/ and below
  ( tar -c /dir/to/copy ) | ( cd /where/to/ && tar -x -p ) Copy (with permissions) copy/ dir to /where/to/ dir
  ( cd /dir/to/copy && tar -c . ) | ( cd /where/to/ && tar -x -p ) Copy (with permissions) contents of copy/ dir to /where/to/
  ( tar -c /dir/to/copy ) | ssh -C user@remote ‘cd /where/to/ && tar -x -p’ Copy (with permissions) copy/ dir to remote:/where/to/ dir
  dd bs=1M if=/dev/sda | gzip | ssh user@remote ‘dd of=sda.gz’ Backup harddisk to remote machine
rsync (Network efficient file copier: Use the –dry-run option for testing)
  rsync -P rsync://rsync.server.com/path/to/file file Only get diffs. Do multiple times for troublesome downloads
  rsync –bwlimit=1000 fromfile tofile Locally copy with rate limit. It’s like nice for I/O
  rsync -az -e ssh –delete ~/public_html/ remote.com:’~/public_html’ Mirror web site (using compression and encryption)
  rsync -auz -e ssh remote:/dir/ . && rsync -auz -e ssh . remote:/dir/ Synchronize current directory with remote one
ssh (Secure SHell)
  ssh $USER@$HOST command Run command on $HOST as $USER (default command=shell)
  ssh -f -Y $USER@$HOSTNAME xeyes Run GUI command on $HOSTNAME as $USER
  scp -p -r $USER@$HOST: file dir/ Copy with permissions to $USER’s home directory on $HOST
  scp -c arcfour $USER@$LANHOST: bigfile Use faster crypto for local LAN. This might saturate GigE
  ssh -g -L 8080:localhost:80 root@$HOST Forward connections to $HOSTNAME:8080 out to $HOST:80
  ssh -R 1434:imap:143 root@$HOST Forward connections from $HOST:1434 in to imap:143
  ssh-copy-id $USER@$HOST Install public key for $USER@$HOST for password-less log in
wget (multi purpose download tool)
  (cd dir/ && wget -nd -pHEKk http://www.example.com/file) Store local browsable version of a page to the current dir
  wget -c http://www.example.com/large.file Continue downloading a partially downloaded file
  wget -r -nd -np -l1 -A ‘*.jpg’ http://www.example.com/dir/ Download a set of files to the current directory
  wget ftp://remote/file[1-9].iso/ FTP supports globbing directly
  wget -q -O- http://www.example/file | grep ‘a href’ | head Process output directly
  echo ‘wget url’ | at 01:00 Download url at 1AM to current dir
  wget –limit-rate=20k url Do a low priority download (limit to 20KB/s in this case)
  wget -nv –spider –force-html -i bookmarks.html Check links in a file
  wget –mirror http://www.example.com/ Efficiently update a local copy of a site (handy from cron)
networking (Note ifconfig, route, mii-tool, nslookup commands are obsolete)
  ethtool eth0 Show status of ethernet interface eth0
  ethtool –change eth0 autoneg off speed 100 duplex full Manually set ethernet interface speed
  iw dev wlan0 link Show link status of wireless interface wlan0
  iw dev wlan0 set bitrates legacy-2.4 1 Manually set wireless interface speed
  iw dev wlan0 scan List wireless networks in range
  ip link show List network interfaces
  ip link set dev eth0 name wan Rename interface eth0 to wan
  ip link set dev eth0 up Bring interface eth0 up (or down)
  ip addr show List addresses for interfaces
  ip addr add 1.2.3.4/24 brd + dev eth0 Add (or del) ip and mask (255.255.255.0)
  ip route show List routing table
  ip route add default via 1.2.3.254 Set default gateway to 1.2.3.254
  ss -tupl List internet services on a system
  ss -tup List active connections to/from system
  host pixelbeat.org Lookup DNS ip address for name or vice versa
  hostname -i Lookup local ip address (equivalent to host `hostname`)
  whois pixelbeat.org Lookup whois info for hostname or ip address
windows networking (Note samba is the package that provides all this windows specific networking support)
  smbtree Find windows machines. See also findsmb
  nmblookup -A 1.2.3.4 Find the windows (netbios) name associated with ip address
  smbclient -L windows_box List shares on windows machine or samba server
  mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/share Mount a windows share
  echo ‘message’ | smbclient -M windows_box Send popup to windows machine (off by default in XP sp2)
text manipulation (Note sed uses stdin and stdout. Newer versions support inplace editing with the -i option)
  sed ‘s/string1/string2/g’ Replace string1 with string2
  sed ‘s/\(.*\)1/\12/g’ Modify anystring1 to anystring2
  sed ‘/^ *#/d; /^ *$/d’ Remove comments and blank lines
  sed ‘:a; /\\$/N; s/\\\n//; ta’ Concatenate lines with trailing \
  sed ‘s/[ \t]*$//’ Remove trailing spaces from lines
  sed ‘s/\([`”$\]\)/\\\1/g’ Escape shell metacharacters active within double quotes
  seq 10 | sed “s/^/      /; s/ *\(.\{7,\}\)/\1/” Right align numbers
  seq 10 | sed p | paste – – Duplicate a column
  sed -n ‘1000{p;q}’ Print 1000th line
  sed -n ‘10,20p;20q’ Print lines 10 to 20
  sed -n ‘s/.*<title>\(.*\)<\/title>.*/\1/ip;T;q’ Extract title from HTML web page
  sed -i 42d ~/.ssh/known_hosts Delete a particular line
  sort -t. -k1,1n -k2,2n -k3,3n -k4,4n Sort IPV4 ip addresses
  echo ‘Test’ | tr ‘[:lower:]’ ‘[:upper:]’ Case conversion
  tr -dc ‘[:print:]’ < /dev/urandom Filter non printable characters
  tr -s ‘[:blank:]’ ‘\t’ </proc/diskstats | cut -f4 cut fields separated by blanks
  history | wc -l Count lines
  seq 10 | paste -s -d ‘ ‘ Concatenate and separate line items to a single line
set operations (Note you can export LANG=C for speed. Also these assume no duplicate lines within a file)
  sort -u file1 file2 Union of unsorted files
  sort file1 file2 | uniq -d Intersection of unsorted files
  sort file1 file1 file2 | uniq -u Difference of unsorted files
  sort file1 file2 | uniq -u Symmetric Difference of unsorted files
  join -t’\0′ -a1 -a2 file1 file2 Union of sorted files
  join -t’\0′ file1 file2 Intersection of sorted files
  join -t’\0′ -v2 file1 file2 Difference of sorted files
  join -t’\0′ -v1 -v2 file1 file2 Symmetric Difference of sorted files
math
  echo ‘(1 + sqrt(5))/2’ | bc -l Quick math (Calculate φ). See also bc
  seq -f ‘4/%g’ 1 2 99999 | paste -sd-+ | bc -l Calculate π the unix way
  echo ‘pad=20; min=64; (100*10^6)/((pad+min)*8)’ | bc More complex (int) e.g. This shows max FastE packet rate
  echo ‘pad=20; min=64; print (100E6)/((pad+min)*8)’ | python Python handles scientific notation
  echo ‘pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)’ | gnuplot -persist Plot FastE packet rate vs packet size
  echo ‘obase=16; ibase=10; 64206’ | bc Base conversion (decimal to hexadecimal)
  echo $((0x2dec)) Base conversion (hex to dec) ((shell arithmetic expansion))
  units -t ‘100m/9.58s’ ‘miles/hour’ Unit conversion (metric to imperial)
  units -t ‘500GB’ ‘GiB’ Unit conversion (SI to IEC prefixes). See also numfmt
  units -t ‘1 googol’ Definition lookup
  seq 100 | paste -s -d+ | bc Add a column of numbers. See also add and funcpy
calendar
  cal -3 Display a calendar
  cal 9 1752 Display a calendar for a particular month year
  date -d fri What date is it this friday. See also day
  [ $(date -d ’12:00 today +1 day’ +%d) = ’01’ ] || exit exit a script unless it’s the last day of the month
  date –date=’25 Dec’ +%A What day does xmas fall on, this year
  date –date=’@2147483647′ Convert seconds since the epoch (1970-01-01 UTC) to date
  TZ=’America/Los_Angeles’ date What time is it on west coast of US (use tzselect to find TZ)
  date –date=’TZ=”America/Los_Angeles” 09:00 next Fri’ What’s the local time for 9AM next Friday on west coast US
locales
  printf “%’d\n” 1234 Print number with thousands grouping appropriate to locale
  BLOCK_SIZE=\’1 ls -l Use locale thousands grouping in ls. See also l
  echo “I live in `locale territory`” Extract info from locale database
  LANG=en_IE.utf8 locale int_prefix Lookup locale info for specific country. See also ccodes
  locale -kc $(locale | sed -n ‘s/\(LC_.\{4,\}\)=.*/\1/p’) | less List fields available in locale database
recode (Obsoletes iconv, dos2unix, unix2dos)
  recode -l | less Show available conversions (aliases on each line)
  recode windows-1252.. file_to_change.txt Windows “ansi” to local charset (auto does CRLF conversion)
  recode utf-8/CRLF.. file_to_change.txt Windows utf8 to local charset
  recode iso-8859-15..utf8 file_to_change.txt Latin9 (western europe) to utf8
  recode ../b64 < file.txt > file.b64 Base64 encode
  recode /qp.. < file.qp > file.txt Quoted printable decode
  recode ..HTML < file.txt > file.html Text to HTML
  recode -lf windows-1252 | grep euro Lookup table of characters
  echo -n 0x80 | recode latin-9/x1..dump Show what a code represents in latin-9 charmap
  echo -n 0x20AC | recode ucs-2/x2..latin-9/x Show latin-9 encoding
  echo -n 0x20AC | recode ucs-2/x2..utf-8/x Show utf-8 encoding
CDs
  gzip < /dev/cdrom > cdrom.iso.gz Save copy of data cdrom
  mkisofs -V LABEL -r dir | gzip > cdrom.iso.gz Create cdrom image from contents of dir
  mount -o loop cdrom.iso /mnt/dir Mount the cdrom image at /mnt/dir (read only)
  wodim dev=/dev/cdrom blank=fast Clear a CDRW
  gzip -dc cdrom.iso.gz | wodim -tao dev=/dev/cdrom -v -data – Burn cdrom image (use –prcap to confirm dev)
  cdparanoia -B Rip audio tracks from CD to wav files in current dir
  wodim -v dev=/dev/cdrom -audio -pad *.wav Make audio CD from all wavs in current dir (see also cdrdao)
  oggenc –tracknum=$track track.cdda.wav -o track.ogg Make ogg file from wav file
disk space (See also FSlint)
  ls -lSr Show files by size, biggest last
  du -s * | sort -k1,1rn | head Show top disk users in current dir. See also dutop
  du -hs /home/* | sort -k1,1h Sort paths by easy to interpret disk usage
  df -h Show free space on mounted filesystems
  df -i Show free inodes on mounted filesystems
  fdisk -l Show disks partitions sizes and types (run as root)
  rpm -q -a –qf ‘%10{SIZE}\t%{NAME}\n’ | sort -k1,1n List all packages by installed size (Bytes) on rpm distros
  dpkg-query -W -f=’${Installed-Size;10}\t${Package}\n’ | sort -k1,1n List all packages by installed size (KBytes) on deb distros
  dd bs=1 seek=2TB if=/dev/null of=ext3.test Create a large test file (taking no space). See also truncate
  > file truncate data of file or create an empty file
monitoring/debugging
  tail -f /var/log/messages Monitor messages in a log file
  strace -c ls >/dev/null Summarise/profile system calls made by command
  strace -f -e open ls >/dev/null List system calls made by command
  strace -f -e trace=write -e write=1,2 ls >/dev/null Monitor what’s written to stdout and stderr
  ltrace -f -e getenv ls >/dev/null List library calls made by command
  lsof -p $$ List paths that process id has open
  lsof ~ List processes that have specified path open
  tcpdump not port 22 Show network traffic except ssh. See also tcpdump_not_me
  ps -e -o pid,args –forest List processes in a hierarchy
  ps -e -o pcpu,cpu,nice,state,cputime,args –sort pcpu | sed ‘/^ 0.0 /d’ List processes by % cpu usage
  ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS List processes by mem (KB) usage. See also ps_mem.py
  ps -C firefox-bin -L -o pid,tid,pcpu,state List all threads for a particular process
  ps -p 1,$$ -o etime= List elapsed wall time for particular process IDs
  watch -n.1 pstree -Uacp $$ Display a changing process subtree
  last reboot Show system reboot history
  free -m Show amount of (remaining) RAM (-m displays in MB)
  watch -n.1 ‘cat /proc/interrupts’ Watch changeable data continuously
  udevadm monitor Monitor udev events to help configure rules
system information (see also sysinfo) (‘#’ means root access is required)
  uname -a Show kernel version and system architecture
  head -n1 /etc/issue Show name and version of distribution
  cat /proc/partitions Show all partitions registered on the system
  grep MemTotal /proc/meminfo Show RAM total seen by the system
  grep “model name” /proc/cpuinfo Show CPU(s) info
  lspci -tv Show PCI info
  lsusb -tv Show USB info
  mount | column -t List mounted filesystems on the system (and align output)
  grep -F capacity: /proc/acpi/battery/BAT0/info Show state of cells in laptop battery
  dmidecode -q | less Display SMBIOS/DMI information
  smartctl -A /dev/sda | grep Power_On_Hours How long has this disk (system) been powered on in total
  hdparm -i /dev/sda Show info about disk sda
  hdparm -tT /dev/sda Do a read speed test on disk sda
  badblocks -s /dev/sda Test for unreadable blocks on disk sda
interactive (see also linux keyboard shortcuts)
  readline Line editor used by bash, python, bc, gnuplot, …
  screen Virtual terminals with detach capability, …
  mc Powerful file manager that can browse rpm, tar, ftp, ssh, …
  gnuplot Interactive/scriptable graphing
  links Web browser
  xdg-open . open a file or url with the registered desktop application

 

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