Linux Basic Commands

This is a linux command line reference for common operations.
Examples marked with • are valid/safe to paste without modification into a terminal, so
you may want to keep a terminal window open while reading this so you can cut & paste.
All these commands have been tested both on Fedora and Ubuntu.
See also more linux commands.

Command		Description
•	apropos whatis	Show commands pertinent to string. See also threadsafe
•	man -t man | ps2pdf - > man.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 $HOME directory
	(cd dir && command)	Go to dir, execute command and return to current dir
•	pushd .	Put current dir on stack so you can popd back to it
file searching
•	alias l='ls -l --color=auto'	quick dir listing
•	ls -lrt	List files by date. See also newest and find_mm_yyyy
•	ls /usr/bin | pr -T9 -W$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 $HOST
	ssh -g -L 8080:localhost:80 root@$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
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
	iwconfig eth1	Show status of wireless interface eth1
	iwconfig eth1 rate 1Mb/s fixed	Manually set wireless interface speed
•	iwlist 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
•	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
•	netstat -tupl	List internet services on a system
•	netstat -tup	List active connections to/from system
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
	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'	cut fields separated by blanks
•	history | wc -l	Count lines
set operations (Note you can export LANG=C for speed. Also these assume no duplicate lines within a file)
	sort file1 file2 | uniq	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
•	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)
•	units -t '1 googol'	Definition lookup
•	seq 100 | (tr '\n' +; echo 0) | 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 "tomorrow" +%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 | cut -d= -f1 | xargs locale -kc | 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)
	cdrecord -v dev=/dev/cdrom blank=fast	Clear a CDRW
	gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom -	Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)
	cdparanoia -B	Rip audio tracks from CD to wav files in current dir
	cdrecord -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
•	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 1,2	List info for particular process IDs
•	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
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