FULL A-Z Linux Commands

The descriptions of these Linux commands are based on their manual pages. To access the man page:

man command_name

For eg: man cat

If you find any discrepancy, please feel free to contact for any correction.
Linux Commands – A
Command     Description
accept   Accept or Reject jobs to a destination, such as a printer.
access   Check a user’s RWX permission for a file.
aclocal     GNU autoconf too
aconnect      ALSA sequencer connection manager.
acpi     Show information about the Advanced Configuration and Power Interface.
acpi_available   Check if ACPI functionality exists on the system.
acpid    Informs user-space programs about ACPI events.
addr2line    Used to convert addresses into file names and line numbers.
addresses    Formats for internet mail addresses.
agetty   An alternative Linux Getty
alias    Create an alias for Linux commands
alsactl      Access advanced controls for ALSA soundcard driver.
amidi    Perform read/write operation for ALSA RawMIDI ports.
amixer   Access CLI-based mixer for ALSA soundcard driver.
anacron      Used to run commands periodically.
aplay    Sound recorder and player for CLI.
aplaymidi    CLI utility used to play MIDI files.
apm      Show Advanced Power Management (APM) hardware info on older systems.
apmd     Used to handle events reported by APM BIOS drivers.
apropos      Shows the list of all man pages containing a specific keyword
apt      Advanced Package Tool, a package management system for Debian and derivatives.
apt-get      Command-line utility to install/remove/update packages based on APT system.
aptitude     Another utility to add/remove/upgrade packages based on the APT system.
ar   A utility to create/modify/extract from archives.
arch     Display print machine hardware name.
arecord      Just like aplay, it’s a sound recorder and player for ALSA soundcard driver.
arecordmidi      Record standard MIDI files.
arp      Used to make changes to the system’s ARP cache
as   A portable GNU assembler.
aspell   An interactive spell checker utility.
at   Used to schedule command execution at specified date & time, reading commands from an input file.
atd      Used to execute jobs queued by the at command.
atq      List a user’s pending jobs for the at command.
atrm     Delete jobs queued by the at command.
audiosend    Used to send an audio recording as an email.
aumix    An audio mixer utility.
autoconf     Generate configuration scripts from a TEMPLATE-FILE and send the output to standard output.
autoheader   Create a template header for configure.
automake     Creates GNU standards-compliant Makefiles from template files
autoreconf   Update generated configuration files.
autoscan     Generate a preliminary configure.in
autoupdate   Update a configure.in file to newer autoconf.
awk      Used to find and replace text in a file(s).
Linux Commands – B
Command     Description
badblocks    Search a disk partition for bad sectors.
banner   Used to print characters as a poster.
basename     Used to display filenames with directoy or suffix.
bash     GNU Bourne-Again Shell.
batch    Used to run commands entered on a standard input.
bc   Access the GNU bc calculator utility.
bg   Send processes to the background.
biff     Notify about incoming mail and sender’s name on a system running comsat server.
bind     Used to attach a name to a socket.
bison    A GNU parser generator, compatible with yacc.
break    Used to exit from a loop (eg: for, while, select).
builtin      Used to run shell builtin commands, make custom functions for commands extending their functionality.
bzcmp    Used to call the cmp program for bzip2 compressed files.
bzdiff   Used to call the diff program for bzip2 compressed files.
bzgrep   Used to call grep for bzip2 compressed files.
bzip2    A block-sorting file compressor used to shrink given files.
bzless   Used to apply ‘less’ (show info one page at a time) to bzip2 compressed files.
bzmore   Used to apply ‘more’ (an inferior version of less) to bzip2 compressed files.
Linux Commands – C
Command     Description
cal      Show calendar.
cardctl      Used to control PCMCIA sockets and select configuration schemes.
cardmgr      Keeps an eye on the added/removes sockets for PCMCIA devices.
case     Execute a command conditionally by matching a pattern.
cat      Used to concatenate files and print them on the screen.
cc   GNU C and C++ compiler.
cd   Used to change directory.
cdda2wav     Used to rip a CD-ROM and make WAV file.
cdparanoia   Record audio from CD more reliably using data-verification algorithms.
cdrdao   Used to write all the content specified to a file to a CD all at once.
cdrecord     Used to record data or audio compact discs.
cfdisk   Show or change the disk partition table.
chage    Used to change user password information.
chattr   Used to change file attributes.
chdir    Used to change active working directory.
chfn     Used to change real user name and information.
chgrp    Used to change group ownership for file.
chkconfig    Manage execution of runlevel services.
chmod    Change access permission for a file(s).
chown    Change the owner or group for a file.
chpasswd     Update password in a batch.
chroot   Run a command with root privileges.
chrt     Alter process attributed in real-time.
chsh     Switch login shell.
chvt     Change foreground virtual terminal.
cksum    Perform a CRC checksum for files.
clear    Used to clear the terminal window.
cmp      Compare two files (byte by byte).
col      Filter reverse (and half-reverse) line feeds from the input.
colcrt   Filter nroff output for CRT previewing.
colrm    Remove columns from the lines of a file.
column   A utility that formats its input into columns.
comm     Used to compare two sorted files line by line.
command      Used to execute a command with arguments ignoring shell function named command.
compress     Used to compress one or more file(s) and replacing the originals ones.
continue     Resume the next iteration of a loop.
cp   Copy contents of one file to another.
cpio     Copy files from and to archives.
cpp      GNU C language processor.
cron     A daemon to execute scheduled commands.
crond    Same work as cron.
crontab      Manage crontab files (containing schedules commands) for users.
csplit   Split a file into sections on the basis of context lines.
ctags    Make a list of functions and macro names defined in a programming source file.
cupsd    A scheduler for CUPS.
curl     Used to transfer data from or to a server using supported protocols.
cut      Used to remove sections from each line of a file(s).
cvs      Concurrent Versions System. Used to track file versions, allow storage/retrieval of previous versions, and enables multiple users to work on the same file.
Linux Commands – D
Command     Description
date     Show system date and time.
dc   Desk calculator utility.
dd   Used to convert and copy a file, create disk clone, write disk headers, etc.
ddrescue     Used to recover data from a crashed partition.
deallocvt    Deallocates kernel memory for unused virtual consoles.
debugfs      File system debugger for ext2/ext3/ext4
declare      Used to declare variables and assign attributes.
depmod   Generate modules.dep and map files.
devdump      Interactively displays the contents of device or file system ISO.
df   Show disk usage.
diff     Used to compare files line by line.
diff3    Compare three files line by line.
dig      Domain Information Groper, a DNS lookup utility.
dir      List the contents of a directory.
dircolors    Set colors for ‘ls’ by altering the LS_COLORS environment variable.
dirname      Display pathname after removing the last slash and characters thereafter.
dirs     Show the list of remembered directories.
disable      Restrict access to a printer.
dlpsh    Interactive Desktop Link Protocol (DLP) shell for PalmOS.
dmesg    Examine and control the kernel ring buffer.
dnsdomainname    Show the DNS domain name of the system.
dnssec-keygen    Generate encrypted Secure DNS keys for a given domain name.
dnssec-makekeyset    Produce domain key set from one or more DNS security keys generated by dnssec-keygen.
dnssec-signkey   Sign a secure DNS keyset with key signatures specified in the list of key-identifiers.
dnssec-signzone      Sign a secure DNS zonefile with the signatures in the specified list of key-identifiers.
doexec   Used to run an executable with an arbitrary argv list provided.
domainname   Show or set the name of current NIS (Network Information Services) domain.
dosfsck      Check and repair MS-DOS file systems.
du   Show disk usage summary for a file(s).
dump     Backup utility for ext2/ext3 file systems.
dumpe2fs     Dump ext2/ext3/ext4 file systems.
dumpkeys     Show information about the keyboard driver’s current translation tables.
Linux Commands – E
Command     Desription
e2fsck   Used to check ext2/ext3/ext4 file systems.
e2image      Store important ext2/ext3/ext4 filesystem metadata to a file.
e2label      Show or change the label on an ext2/ext3/ext4 filesystem.
echo     Send input string(s) to standard output i.e. display text on the screen.
ed   GNU Ed – a line-oriented text editor.
edquota      Used to edit filesystem quotas using a text editor, such as vi.
egrep    Search and display text matching a pattern.
eject    Eject removable media.
elvtune      Used to set latency in the elevator algorithm used to schedule I/O activities for specified block devices.
emacs   Emacs text editor command line utility.
enable   Used to enable/disable shell builtin commands.
env      Run a command in a modified environment. Show/set/delete environment variables.
envsubst     Substitute environment variable values in shell format strings.
esd      Start the Enlightenment Sound Daemon (EsounD or esd). Enables multiple applications to access the same audio device simultaneously.
esd-config  Manage EsounD configuration.
esdcat   Use EsounD to send audio data from a specified file.
esdctl   EsounD control program.
esddsp   Used to reroute non-esd audio data to esd and control all the audio using esd.
esdmon   Used to copy the sound being sent to a device. Also, send it to a secondary device.
esdplay      Use EsounD system to play a file.
esdrec   Use EsounD to record audio to a specified file.
esdsample    Sample audio using esd.
etags    Used to create a list of functions and macros from a programming source file. These etags are used by emacs. For vi, use ctags.
ethtool      Used to query and control network driver and hardware settings.
eval     Used to evaluate multiple commands or arguments are once.
ex   Interactive command
exec     An interactive line-based text editor.
exit     Exit from the terminal.
expand   Convert tabs into spaces in a given file and show the output.
expect   An extension to the Tcl script, it’s used to automate interaction with other applications based on their expected output.
export   Used to set an environment variable.
expr     Evaluate expressions and display them on standard output.
Linux Commands – F
Command     Description
factor   Display prime factors of specified integer numbers.
false    Do nothing, unsuccessfully. Exit with a status code indicating failure.
fc-cache     Make font information cache after scanning the directories.
fc-list      Show the list of available fonts.
fdformat     Do a low-level format on a floppy disk.
fdisk    Make changes to the disk partition table.
fetchmail    Fetch mail from mail servers and forward it to the local mail delivery system.
fg   Used to send a job to the foreground.
fgconsole    Display the number of the current virtual console.
fgrep    Display lines from a file(s) that match a specified string. A variant of grep.
file     Determine file type for a file.
find     Do a file search in a directory hierarchy.
finger   Display user data including the information listed in .plan and .project in each user’s home directory.
fingerd      Provides a network interface for the finger program.
flex     Generate programs that perform pattern-matching on text.
fmt      Used to convert text to a specified width by filling lines and removing new lines, displaying the output.
fold     Wrap input line to fit in a specified width.
for      Expand words and run commands for each one in the resultant list.
formail      Used to filter standard input into mailbox format.
format   Used to format disks.
free     Show free and used system memory.
fsck     Check and repair a Linux file system
ftp      File transfer protocol user interface.
ftpd     FTP server process.
function     Used to define function macros.
fuser    Find and kill a process accessing a file.
Linux Commands – G
Command     Description
g++      Run the g++ compiler.
gawk     Used for pattern scanning and language processing. A GNU implementation of AWK language.
gcc      A C and C++ compiler by GNU.
gdb      A utility to debug programs and know about where it crashes.
getent   Shows entries from Name Service Switch Libraries for specified keys.
getkeycodes      Displays the kernel scancode-to-keycode mapping table.
getopts      A utility to parse positional parameters.
gpasswd      Allows an administrator to change group passwords.
gpg      Enables encryption and signing services as per the OpenPGP standard.
gpgsplit     Used to split an OpenPGP message into packets.
gpgv     Used to verify OpenPGP signatures.
gpm      It enables cut and paste functionality and a mouse server for the Linux console.
gprof    Shows call graph profile data.
grep     Searches input files for a given pattern and displays the relevant lines.
groff    Serves as the front-end of the groff document formatting system.
groffer      Displays groff files and man pages.
groupadd     Used to add a new user group.
groupdel     Used to remove a user group.
groupmod     Used to modify a group definition.
groups   Show the group(s) to which a user belongs.
grpck    Verifies the integrity of group files.
grpconv      Creates a gshadow file from a group or an already existing gshadow.
gs   Invokes Ghostscript, and interpreter and previewer for Adobe’s PostScript and PDF languages.
gunzip   A utility to compress/expand files.
gzexe    Used compress executable files in place and have them automatically uncompress and run at a later stage.
gzip     Same as gzip.
Linux Commands – H
Command     Description
halt     Command used to half the machine.
hash     Shows the path for the commands executed in the shell.
hdparm   Show/configure parameters for SATA/IDE devices.
head     Shows first 10 lines from each specified file.
help     Display’s help for a built-in command.
hexdump      Shows specified file output in hexadecimal, octal, decimal, or ASCII format.
history      Shows the command history.
host     A utility to perform DNS lookups.
hostid   Shows host’s numeric ID in hexadecimal format.
hostname     Display/set the hostname of the system.
htdigest     Manage the user authentication file used by the Apache web server.
htop     An interactive process viewer for the command line.
hwclock      Show or configure the system’s hardware clock.
Linux Commands – I
Command     Description
iconv    Convert text file from one encoding to another.
id   Show user and group information for a specified user.
if   Execute a command conditionally.
ifconfig     Used to configure network interfaces.
ifdown   Stops a network interface.
ifup     Starts a network interface.
imapd    An IMAP (Interactive Mail Access Protocol) server daemon.
import   Capture an X server screen and saves it as an image.
inetd    Extended internet services daemon, it starts the programs that provide internet services.
info     Used to read the documentation in Info format.
init     Systemd system and service manager.
insmod   A program that inserts a module into the Linux kernel.
install      Used to copy files to specified locations and set attributions during the install process.
iostat   Shows statistics for CPU, I/O devices, partitions, network filesystems.
ip   Display/manipulate routing, devices, policy, routing and tunnels.
ipcrm    Used to remove System V interprocess communication (IPC) objects and associated data structures.
ipcs     Show information on IPC facilities for which calling process has read access.
iptables     Administration tool for IPv4 packet filtering and NAT.
iptables-restore     Used to restore IP tables from data specified in the input or a file.
iptables-save    Used to dump IP table contents to standard output.
isodump      A utility that shows the content iso9660 images to verify the integrity of directory contents.
isoinfo      A utility to perform directory like listings of iso9660 images.
isosize      Show the length of an iso9660 filesystem contained in a specified file.
isovfy   Verifies the integrity of an iso9660 image.
ispell   A CLI-based spell-check utility.
Linux Commands – J
Command     Description
jobs     Show the list of active jobs and their status.
join     For each pair of input lines, join them using a command field and display on standard output.
Linux Commands – K
Command     Description
kbd_mode     Set a keyboard mode. Without arguments, shows the current keyboard mode.
kbdrate      Reset keyboard repeat rate and delay time.
kill     Send a kill (termination) signal to one more processes.
killall      Kills a process(es) running a specified command.
killall5     A SystemV killall command. Kills all the processes excluding the ones which it depends on.
klogd    Control and prioritize the kernel messages to be displayed on the console, and log them through syslogd.
kudzu    Used to detect new and enhanced hardware by comparing it with existing database. Only for RHEL and derivates.
Linux Commands – L
Command     Description
last     Shows a list of recent logins on the system by fetching data from /var/log/wtmp file.
lastb    Shows the list of bad login attempts by fetching data from /var/log/btmp file.
lastlog      Displays information about the most recent login of all users or a specified user.
ld   The Unix linker, it combines archives and object files. It then puts them into one output file, resolving external references.
ldconfig     Configure dynamic linker run-time bindings.
ldd      Shows shared object dependencies.
less     Displays contents of a file one page at a time. It’s advanced than more command.
lesskey      Used to specify key bindings for less command.
let      Used to perform integer artithmetic on shell variables.
lftp     An FTP utility with extra features.
lftpget      Uses lftop to retrieve HTTP, FTP, and other protocol URLs supported by lftp.
link     Create links between two files. Similar to ln command.
ln   Create links between files. Links can be hard (two names for the same file) or soft (a shortcut of the first file).
loadkeys     Load keyboard translation tables.
local    Used to create function variables.
locale   Shows information about current or all locales.
locate   Used to find files by their name.
lockfile     Create semaphore file(s) which can be used to limit access to a file.
logger   Make entries in the system log.
login    Create a new session on the system.
logname      Shows the login name of the current user.
logout   Performs the logout operation by making changes to the utmp and wtmp files.
logrotate    Used for automatic rotation, compression, removal, and mailing of system log files.
look     Shows any lines in a file containing a given string in the beginning.
losetup      Set up and control loop devices.
lpadmin      Used to configure printer and class queues provided by CUPS (Common UNIX Printing System).
lpc      Line printer control program, it provides limited control over CUPS printer and class queues.
lpinfo   Shows the list of avaiable devices and drivers known to the CUPS server.
lpmove   Move on or more printing jobs to a new destination.
lpq      Shows current print queue status for a specified printer.
lpr      Used to submit files for printing.
lprint   Used to print a file.
lprintd      Used to abort a print job.
lprintq      List the print queue.
lprm     Cancel print jobs.
lpstat   Displays status information about current classes, jobs, and printers.
ls   Shows the list of files in the current directory.
lsattr   Shows file attributes on a Linux ext2 file system.
lsblk    Lists information about all available or the specified block devices.
lsmod    Show the status of modules in the Linux kernel.
lsof     List open files.
lspci    List all PCI devices.
lsusb    List USB devices.
Linux Commands – M
Command     Description
m4   Macro processor.
mail     Utility to compose, receive, send, forward, and reply to emails.
mailq    Shows to list all emails queued for delivery (sendmail queue).
mailstats    Shows current mail statistics.
mailto   Used to send mail with multimedia content in MIME format.
make     Utility to maintain groups of programs, recompile them if needed.
makedbm      Creates an NIS (Network Information Services) database map.
makemap      Creates database maps used by the keyed map lookups in sendmail.
man      Shows manual pages for Linux commands.
manpath      Determine search path for manual pages.
mattrib      Used to change MS-DOS file attribute flags.
mbadblocks   Checks MD-DOS filesystems for bad blocks.
mcat     Dump raw disk image.
mcd      Used to change MS-DOS directory.
mcopy    Used to copy MS-DOS files from or to Unix.
md5sum   Used to check MD5 checksum for a file.
mdel, mdeltree   Used to delete MS-DOS file. mdeltree recursively deletes MS-DOS directory and its contents.
mdir     Used to display an MS-DOS directory.
mdu      Used to display the amount of space occupied by an MS-DOS directory.
merge    Three-way file merge. Includes all changes from file2 and file3 to file1.
mesg     Allow/disallow osends to sedn write messages to your terminal.
metamail    For sending and showing rich text or multimedia email using MIME typing metadata.
metasend      An interface for sending non-text mail.
mformat      Used to add an MS-DOS filesystem to a low-level formatted floppy disk.
mimencode    Translate to/from MIME multimedia mail encoding formats.
minfo    Display parameters of an MS-DOS filesystem.
mkdir    Used to create directories.
mkdosfs      Used to create an MS-DOS filesystem under Linux.
mke2fs   Used create an ext2/ext3/ext4 filesystem.
mkfifo   Used to create named pipes (FIFOs) with the given names.
mkfs     Used to build a Linux filesystem on a hard disk partition.
mkfs.ext3    Same as mke2fs, create an ext3 Linux filesystem.
mkisofs      Used to create an ISO9660/JOLIET/HFS hybrid filesystem.
mklost+found     Create a lost+found directory on a mounted ext2 filesystem.
mkmanifest   Makes a list of file names and their DOS 8.3 equivalent.
mknod    Create a FIFO, block (buffered) special file, character (unbuffered) special file with the specified name.
mkraid   Used to setup RAID device arrays.
mkswap   Set up a Linux swap area.
mktemp   Create a temporary file or directory.
mlabel   Make an MD-DOS volume label.
mmd      Make an MS-DOS subdirectory.
mmount   Mount an MS-DOS disk.
mmove    Move or rename an MS-DOS file or subdirectory.
mmv      Mass move and rename files.
modinfo      Show information about a Linux kernel module.
modprobe     Add or remove modules from the Linux kernel.
more     Display content of a file page-by-page.
most     Browse or page through a text file.
mount    Mount a filesystem.
mountd   NFS mount daemon.
mpartition   Partition an MS-DOS disk.
mpg123   Command-line mp3 player.
mpg321   Similar to mpg123.
mrd      Remove an MS-DOS subdirectory.
mren     Rename an existing MS-DOS file.
mshowfat     Show FTA clusters allocated to a file.
mt   Control magnetic tape drive operation.
mtools   Utilities to access MS-DOS disks.
mtoolstest   Tests and displays the mtools configuration files.
mtr      A network diagnostic tool.
mtype    Display contents of an MS-DOS file.
mv   Move/rename files or directories.
mzip     Change protection mode and eject disk on Zip/Jaz drive.
Linux Commands – N
Command     Description
named    Internet domain name server.
namei    Follow a pathname until a terminal point is found.
nameif   Name network interfaces based on MAC addresses.
nc   Netcat utility. Arbitrary TCP and UDP connections and listens.
netstat      Show network information.
newaliases   Rebuilds mail alias database.
newgrp   Log-in to a new group.
newusers     Update/create new users in batch.
nfsd     Special filesystem for controlling Linux NFS server.
nfsstat      List NFS statistics.
nice     Run a program with modified scheduling priority.
nl   Show numbered line while displaying the contents of a file.
nm   List symbols from object files.
nohup    Run a command immune to hangups.
notify-send      A program to send desktop notifications.
nslookup     Used performs DNS queries. Read this article for more info.
nsupdate     Dynamic DNS update utility.
Linux Commands – O
Command     Description
objcopy      Copy and translate object files.
objdump      Display information from object files.
od   Dump files in octal and other formats.
op   Operator access, allows system administrators to grant users access to certain root operations that require superuser privileges.
open     Open a file using its default application.
openvt   Start a program on a new virtual terminal (VT).
Linux Commands – P
Command     Description
passwd   Change user password.
paste    Merge lines of files. Write to standard output, TAB-separated lines consisting of sqentially correspnding lines from each file.
patch    Apply a patchfile (containing differences listing by diff program) to an original file.
pathchk      Check if file names are valid or portable.
perl     Perl 5 language interpreter.
pgrep    List process IDs matching the specified criteria among all the running processes.
pidof    Find process ID of a running program.
ping     Send ICMP ECHO_REQUEST to network hosts.
pinky    Lightweight finger.
pkill    Send kill signal to processes based on name and other attributes.
pmap     Report memory map of a process.
popd     Removes directory on the head of the directory stack and takes you to the new directory on the head.
portmap      Converts RPC program numbers to IP port numbers.
poweroff     Shuts down the machine.
pppd     Point-to-point protocol daemon.
pr   Convert (column or paginate) text files for printing.
praliases    Prints the current system mail aliases.
printcap     Printer capability database.
printenv     Show values of all or specified environment variables.
printf   Show arguments formatted according to a specified format.
ps   Report a snapshot of the current processes.
ptx      Produce a permuted index of file contents.
pushd    Appends a given directory name to the head of the stack and then cd to the given directory.
pv   Monitor progress of data through a pipe.
pwck     Verify integrity of password files.
pwconv   Creates shadow from passwd and an optionally existing shadow.
pwd      Show current directory.
python
Linux Commands – Q
Command     Description
quota    Shows disk usage, and space limits for a user or group. Without arguments, only shows user quotas.
quotacheck   Used to scan a file system for disk usage.
quotactl     Make changes to disk quotas.
quotaoff     Enable enforcement of filesystem quotas.
quotaon      Disable enforcement of filesystem quotas.
quotastats   Shows the report of quota system statistics gathered from the kernel.
Linux Commands – R
Command     Description
raidstart    Start/stop RAID devices.
ram      RAM disk device used to access the RAM disk in raw mode.
ramsize      Show usage information for the RAM disk.
ranlib   Generate index to the contents of an archive and store it in the archive.
rar      Create and manage RAR file in Linux.
rarpd    Respond to Reverse Address Resoultion Protocol (RARP) requests.
rcp      Remote copy command to copy files between remote computers.
rdate    Set system date and time by fetching information from a remote machine.
rdev     Set or query RAM disk size, image root device, or video mode.
rdist    Remote file distribution client, maintains identical file copies over multiple hosts.
rdistd   Start the rdist server.
read     Read from a file descriptor.
readarray    Read lines from a file into an array variable.
readcd   Read/write compact disks.
readelf      Shows information about ELF (Executable and Linkable fomrat) files.
readlink     Display value of a symbolic link or canonical file name.
readonly     Mark functions and variables as read-only.
reboot   Restart the machine.
reject   Accept/reject print jobs sent to a specified destination.
remsync      Synchronize remote files over email.
rename   Rename one or more files.
renice   Change priority of active processes.
repquota     Report disk usage and quotas for a specified filesystem.
reset    Reinitialize the terminal.
resize2fs    Used to resize ext2/ext3/ext4 file systems.
restore      Restore files from a backup created using dump.
return   Exit a shell function.
rev      Show contents of a file, reversing the order of characters in every line.
rexec    Remote execution client for exec server.
rexecd   Remote execution server.
richtext     View “richtext” on an ACSII terminal.
rlogin   Used to connect a local host system with a remote host.
rlogind      Acts as the server for rlogin. It facilitates remote login, and authentication based on privileged port numbers from trusted hosts.
rm   Removes specified files and directories (not by default).
rmail    Handle remote mail received via uucp.
rmdir    Used to remove empty directories.
rmmod    A program to remove modules from Linux kernel.
rndc     Name server control utility. Send command to a BIND DNS server over a TCP connection.
rootflags    Show/set flags for the kernel image.
route    Show/change IP routing table.
routed   A daemon, invoked at boot time, to manage internet routing tables.
rpcgen   An RPC protocol compiler. Parse a file written in the RPC language.
rpcinfo      Shows RPC information. Makes an RPC call to an RPC server and reports the findings.
rpm      A package manager for linux distributions. Originally developed for RedHat Linux.
rsh      Remote shell. Connects to a specified host and executes commands.
rshd     A daemon that acts as a server for rsh and rcp commands.
rsync    A versitile to for copying files remotely and locally.
runlevel     Shows previous and current SysV runlevel.
rup      Remote status display. Shows current system status for all or specified hosts on the local network.
ruptime      Shows uptime and login details of the machines on the local network.
rusers   Shows the list of the users logged-in to the host or on all machines on the local network.
rusersd      The rsuerd daemon acts as a server that responds to the queries from rsuers command.
rwall    Sends messages to all users on the local network.
rwho     Reports who is logged-in to the hosts on the local network.
rwhod    Acts as a server for rwho and ruptime commands.
Linux Commands – S
Command     Description
sane-find-scanner    Find SCSI and USB scanner and determine their device files.
scanadf      Retrieve multiple images from a scanner equipped with an automatic document feeder (ADF).
scanimage    Read images from image aquistion devices (scanner or camera) and display on standard output in PNM (Portable aNyMap) format.
scp      Copy files between hosts on a network securely using SSH.
screen   A window manager that enables multiple pseudo-terminals with the help of ANSI/VT100 terminal emulation.
script   Used to make a typescript of everything displayed on the screen during a terminal session.
sdiff    Shows two files side-by-side and highlights the differences.
sed      Stream editor for filtering and transforming text (from a file or a pipe input).
select   Synchronous I/O multiplexing.
sendmail     It’s a mail router or an MTA (Mail Transfer Agent). sendmail support can send a mail to one or more recepients using necessary protocols.
sensors      Shows the current readings of all sensor chips.
seq      Displays an incremental sequence of numbers from first to last.
set      Used to manipulate shell variables and functions.
setfdprm     Sets floppy disk parameters as provided by the user.
setkeycodes      Load kernel scancode-to-keycode mapping table entries.
setleds      Show/change LED light settings of the keyboard.
setmetamode      Define keyboard meta key handling. Without arguments, shows current meta key mode.
setquota     Set disk quotas for users and groups.
setsid   Run a program in a new session.
setterm      Set terminal attributes.
sftp     Secure File Transfer program.
sh   Command interpreter (shell) utility.
sha1sum      Compute and check 160-bit SHA1 checksum to verify file integrity.
shift    Shift positional parameters.
shopt    Shell options.
showkey      Examines codes sent by the keyboard displays them in printable form.
showmount    Shows information about NFS server mount on the host.
shred    Overwrite a file to hide its content (optionally delete it), making it harder to recover it.
shutdown     Power-off the machine.
size     Lists section size and the total size of a specified file.
skill    Send a signal to processes.
slabtop      Show kernel slab cache information in real-time.
slattach     Attack a network interface to a serial line.
sleep    Suspend execution for a specified amount of time (in seconds).
slocate      Display matches by searching filename databases. Takes ownership and file permission into consideration.
snice    Reset priority for processes.
sort     Sort lines of text files.
source   Run commands from a specified file.
split    Split a file into pieces of fixed size.
ss   Display socket statistics, similar to netstat.
ssh      An SSH client for logging in to a remote machine. It provides encrypted communication between the hosts.
ssh-add      Adds private key identities to the authentication agent.
ssh-agent    It holds private keys used for public key authentication.
ssh-keygen   It generates, manages, converts authentication keys for ssh.
ssh-keyscan      Gather ssh public keys.
sshd     Server for the ssh program.
stat     Display file or filesystem status.
statd    A daemon that listens for reboot notifications from other hosts, and manages the list of hosts to be notified when the local system reboots.
strace   Trace system calls and signals.
strfile      Create a random access file for storing strings.
strings      Search a specified file and prints any printable strings with at least four characters and followed by an unprintable character.
strip    Discard symbols from object files.
stty     Change and print terminal line settings.
su   Change user ID or become superuser.
sudo     Execute a command as superuser.
sum      Checksum and count the block in a file.
suspend      Suspend the execution of the current shell.
swapoff      Disable devices for paging and swapping.
swapon   Enable devices for paging and swapping.
symlink      Create a symbolic link to a file.
sync     Synchronize cached writes to persistent storage.
sysctl   Configure kernel parameters at runtime.
sysklogd     Linux system logging utilities. Provides syslogd and klogd functionalities.
syslogd      Read and log system messages to the system console and log files.
Linux Commands – T
Command     Description
tac      Concatenate and print files in reverse order. Opposite of cat command.
tail     Show the last 10 lines of each specified file(s).
tailf    Follow the growth of a log file. (Deprecated command)
talk     A two-way screen-oriented communication utility that allows two user to exchange messages simulateneously.
talkd    A remote user communication server for talk.
tar      GNU version of the tar archiving utility. Used to store and extract multiple files from a single archive.
taskset      Set/retrieve a process’s CPU affinity.
tcpd     Access control utility for internet services.
tcpdump      Dump traffic on network. Displays a description of the contents of packets on a network interface that match the boolean expression.
tcpslice     Extract pieces of tcpdump files or merge them.
tee      Read from standard input and write to standard output and files.
telinit      Change SysV runlevel.
telnet   Telnet protocol user interface. Used to interact with another host using telnet.
telnetd      A server for the telnet protocol.
test     Check file type and compare values.
tftp     User interface to the internet TFTP (Trivial File Transfer Protocol).
tftpd    TFTP server.
time     Run programs and summarize system resource usage.
timeout      Execute a command with a time limit.
times    Shows accumulated user and system times for the shell and it’s child processes.
tload    Shows a graph of the current system load average to the specified tty.
tmpwatch     Recursively remove files and directories which haven’t been accessed for the specified period of time.
top      Displays real-time view of processes running on the system.
touch    Change file access and modification times.
tput     Modify terminal-dependent capabilities, color, etc.
tr   Translate, squeeze, or delete characters from standard input and display on standard output.
tracepath    Traces path to a network host discovering MTU (Maximum Transmission Unit) along this path.
traceroute   Traces the route taken by the packets to reach the network host.
trap     Trap function responds to hardware signals. It defines and creates handlers to run when the shell receives signals.
troff    The troff processor of the groff text formatting system.
TRUE     Exit with a status code indicating success.
tset     Initialize terminal.
tsort    Perform topological sort.
tty      Display the filename of the terminal connected to standard input.
tune2fs      Adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems.
tunelp   Set various parameters for the line printer devices.
type     Write a description for a command type.
Linux Commands – U
Command     Description
ul   Underline text.
ulimit   Get and set user limits for the calling process.
umask    Set file mode creation mask.
umount   Unmount specified file systems.
unalias      Remove alias definitions for specified alias names.
uname    Show system information.
uncompress  Uncompress the files compressed with the compress command.
unexpand     Convert spaces to tabs for a specified file.
unicode_start    Put keyboard and console in Unicode mode.
unicode_stop     Revert keyboard and console from Unicode mode.
uniq     Report or omit repeating lines.
units    Convert units from one scalar to another.
unrar    Extract files from a RAR archive.
unset    Remove variable or function names.
unshar   Unpack shell archive scripts.
until    Execute command until a given condition is true.
uptime   Tell how long the system has been running.
useradd      Create a new user or update default user information.
userdel      Delete a user account and related files.
usermod      Modify a user account.
users    Show the list of active users on the machine.
usleep   Suspend execution for microsecond intervals.
uudecode     Decode a binary file.
uuencode     Encode a binary file.
uuidgen      Created a new UUID (Universally Unique Identifier) table.
Linux Commands – V
Command     Description
vdir     Same as ls -l -b. Verbosely list directory contents.
vi   A text editor utility.
vidmode      Set the video mode for a kernel image. Displays current mode value without arguments. Alternative: rdev -v
vim      Vi Improved, a text-based editor which is a successor to vi.
vmstat  Shows information about processes, memory, paging, block IO, traps, disks, and CPU activity.
volname      Returns volume name for a device formatted with an ISO-9660 filesystem. For example, CD-ROM.
Linux Commands – W
Command     Description
w    Show who is logged-on and what they’re doing.
wait     Waits for a specified process ID(s) to terminate and returns the termination status.
wall     Display a message on the terminals all the users who are currently logged-in.
warnquota    Send mail to the users who’ve exceeded their disk quota soft limit.
watch    Runs commands repeatedly until interr
zdump    Displays time for the timezone mentioned.upted and shows their output and errors.
wc   Print newline, word, and byte count for each of the specified files.
wget     A non-interactive file download utility.
whatis   Display one line manual page descriptions.
whereis      Locate the binary, source, and man page files for a command.
which    For a given command, lists the pathnames for the files which would be executed when the command runs.
while    Conditionally execute commands (while loop).
who      Shows who is logged on.
whoami   Displays the username tied to the current effective user ID.
whois    Looks for an object in a WHOIS database
write    Display a message on other user’s terminal.
Linux Commands – X
Command     Description
xargs    Runs a command using initial arguments a
zdump    Displays time for the timezone mentioned.nd then reads remaining arguments from standard input.
xdg-open     Used to open a file or URL in an application preferred by the user.
xinetd   Extended internet services daemon. Works similar to inetd.
xz   Compress/ Decompress .xz and .lzma files.
Linux Commands – Y
Command     Description
yacc     Yet Another Compiler Compiler, a GNU Project parser generator.
yes      Repeatedly output a line with a specified string(s) until killed.
ypbind   A daemon that helps client processes to connect to an NIS server.
ypcat    Shows the NIS map (or database) for the specified MapName parameter.
ypinit   Sets up NIS maps on an NIS server.
ypmatch      Shows values for specified keys from an NIS map.
yppasswd     Change NIS login password.
yppasswdd    Acts as a server for the yppasswd command. Receives and executes requests.
yppoll   Shows the ID number or version of NIS map currently used on the NIS server.
yppush   Forces slave NIS servers to copy updated NIS maps.
ypserv   A daemon activated at system startup. It looks for information in local NIS maps.
ypset    Point a client (running ypbind) to a specifc server (running ypserv).
yptest   Calls various functions to check the configuration of NIS services.
ypwhich      Shows the hostname for NIS server or master server for a given map.
ypxfr    Transfers NIS server map from server to a local host.
Linux Commands – Z
Command     Description
zcat     Used to compress/uncompress files. Similar to gzip
zcmp     Compare compressed files.
zdiff    Compare compressed files line by line.
zdump    Displays time for the timezone mentioned.
zforce   Adds .gz extension to all gzipped files.
zgrep    Performs grep on compressed files.
zic      Creates time conversion information files using the specified input files.
zip      A file compression and packaging utility.
zless    Displays information of a compressed file (using less command) on the terminal one screen at a time.
zmore    Displays output of a compressed file (using more command) on the terminal one page at a time.
znew     Recompress .z files to .gz. files.