Linux Commands : A practical reference

Command Description • apropos whatis Show commands pertinent to string. See also threadsafeman -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 $HOME directory   (cd dir && command) Go to dir, execute command and return to current dir • pushd . Put current dir on stack so you can popd back to it file searchingalias l=’ls -l –color=auto’ quick dir listing. See also l • ls -lrt List files by date. See also newest and find_mm_yyyy • ls /usr/bin | pr -T9 -W$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:// 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/’~/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 Store local browsable version of a page to the current dir   wget -c Continue downloading a partially downloaded file   wget -r -nd -np -l1 -A ‘*.jpg’ Download a set of files to the current directory   wget ftp://remote/file[1-9].iso/ FTP supports globbing directly • wget -q -O- | 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 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 brd + dev eth0 Add (or del) ip and mask ( • ip route show List routing table   ip route add default via Set default gateway to • ss -tupl List internet services on a system • ss -tup List active connections to/from system • host Lookup DNS ip address for name or vice versa • hostname -i Lookup local ip address (equivalent to host `hostname`) • whois 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 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 $$ List paths that process id has open • lsof ~ List processes that have specified path open • tcpdump not port 22 Show network traffic except ssh. See also tcpdump_not_me • ps -e -o pid,args –forest List processes in a hierarchy • ps -e -o pcpu,cpu,nice,state,cputime,args –sort pcpu | sed ‘/^ 0.0 /d’ List processes by % cpu usage • ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS List processes by mem (KB) usage. See also • ps -C firefox-bin -L -o pid,tid,pcpu,state List all threads for a particular process • ps -p 1,$$ -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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