Command Description apropos whatis Show commands pertinent to string. You may need to first run: sudo mandb 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 $HOME directory (cd dir && command) Go to dir, execute command and return to current dir pushd . Put current dir on stack so you can popd back to it file searching • alias l='ls -l --color=auto' quick dir listing. See also l • ls -lrt List files by date. See also newest and find_mm_yyyy • ls /usr/bin | pr -T9 -W$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.pixelbeat.org/cmdline.html) 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.pixelbeat.org/timeline.html | 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>.*/\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). See also bc hex padding • 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