Ultimate A‑Z Linux Command Cheat Sheet for Sysadmins

This article is a comprehensive alphabetical reference of Linux command‑line utilities. For each command it provides a concise description of its purpose and typical usage, making it a handy lookup for system administrators, developers, and power users.

A

access : Check whether the calling process can access a specified file (e.g., test for existence or permissions).

accton : Enable or disable the accounting daemon or change the accounting file.

aclocal : Generate aclocal.m4 from configure.in for GNU Autotools.

acpi : Display battery status and other ACPI information.

acpi_available : Test whether the ACPI subsystem is available.

acpid : Daemon that notifies user‑space programs of ACPI events.

addr2line : Convert an address into a file name and line number (useful for debugging).

agetty : Linux version of getty, manages virtual or physical terminals for multi‑user access.

alias : Define a string substitution for a command in the shell.

amixer : Command‑line mixer for ALSA sound drivers.

aplay : Play audio files using ALSA.

aplaymidi : Send standard MIDI files to an ALSA MIDI port.

apropos : Search the manual page database for keywords when the exact command name is unknown.

apt : High‑level package manager front‑end for Debian‑based systems.

apt-get : Low‑level package handling tool (install, remove, update).

aptitude : Text‑based interface to the APT system with advanced dependency handling.

ar : Create, modify, and extract files from archive libraries.

arch : Print the machine architecture.

arp : Manipulate the kernel ARP cache.

aspell : Spell‑checking utility.

atd : Daemon that runs jobs scheduled by at.

atrm : Remove jobs from the at queue.

atq : List pending at jobs.

autoconf : Generate configuration scripts for source packages.

autoheader : Create template header files for configure.

automake : Generate GNU‑standard Makefile.in files.

autoreconf : Recreate the build system configuration files.

autoupdate : Update configure.in to newer Autoconf syntax.

awk : Pattern‑scanning and processing language for text manipulation.

B

banner : Print large ASCII banners to standard output.

basename : Strip directory and suffix from a pathname.

batch : Execute commands when system load is below a threshold (default 1.5).

bc : Arbitrary‑precision calculator language.

bg : Move a stopped or backgroundable job to the background.

biff : Mail notification service that alerts when new mail arrives.

bind : Set Readline key bindings and variables.

bison : Parser generator compatible with Yacc.

break : Exit from a for, while, or until loop.

builtin : Execute a shell builtin with arguments.

bzcmp : Compare bzip2‑compressed files using cmp.

bzdiff : Diff bzip2‑compressed files.

bzgrep : Grep inside bzip2‑compressed files.

bzip2 : Compress or decompress files using the Burrows‑Wheeler algorithm.

bzless : View bzip2‑compressed files without fully decompressing.

bzmore : Pager for bzip2‑compressed files.

C

cal : Display a calendar for a given month or year.

case : Shell construct for multi‑branch conditional execution.

cat : Concatenate files and print to standard output.

cc : Compile C source files (often a wrapper for gcc).

ccrypt : Encrypt or decrypt files using the Rijndael cipher.

cd : Change the current working directory.

cfdisk : Text‑based partition table editor.

chage : Modify user password expiry information.

chattr : Change file attributes on a Linux filesystem.

chfn : Change a user's full name and other GECOS fields.

chgrp : Change group ownership of files.

chkconfig : List and modify service run‑level settings (SysV init).

chmod : Change file permission bits.

chown : Change file owner and group.

chpasswd : Update passwords for multiple users from a file.

chroot : Change the apparent root directory for a process.

chrt : Set real‑time scheduling attributes for a process.

chsh : Change a user's login shell.

chvt : Switch between virtual terminals.

cksum : Compute and display a CRC checksum.

clear : Clear the terminal screen.

cmp : Compare two files byte by byte.

col : Filter reverse line feeds from input.

colcrt : Format output for CRT displays.

colrm : Remove selected columns from a file.

column : Format input into multiple columns.

comm : Compare two sorted files line by line.

compress : Reduce file size using LZW compression (creates .Z files).

continue : Skip the remainder of a loop iteration.

cp : Copy files or directories.

cpio : Copy files to and from archives (similar to tar).

cpp : C preprocessor.

cron : Schedule recurring tasks.

crontab : Edit the list of scheduled cron jobs.

csplit : Split a file into sections based on context lines.

ctags : Generate an index (tags) file for source code navigation.

cupsd : Scheduler daemon for the CUPS printing system.

curl : Transfer data from or to a server using supported protocols (HTTP, FTP, etc.).

cut : Remove sections from each line of files.

cvs : Version control system for tracking file revisions.

D

date : Display or set the system date and time.

dc : Reverse‑Polish notation calculator.

dd : Convert and copy raw data; often used for creating bootable images.

declare : Declare variables and functions in Bash, optionally setting attributes.

depmod : Generate module dependency information for the kernel.

df : Report file system disk space usage.

diff : Show line‑by‑line differences between two files.

diff3 : Compare three files simultaneously.

dir : List directory contents (similar to ls).

dirname : Strip the last component from a pathname.

dirs : Show the list of remembered directories (stack).

disable : Disable a printer or class (CUPS).

dmesg : Print kernel ring buffer messages.

dmidecode : Dump DMI (SMBIOS) table contents – hardware details.

domainname : Show or set the NIS domain name.

dos2unix : Convert DOS line endings to Unix format.

dosfsck : Check and repair DOS/Windows file systems.

dstat : Versatile resource statistics tool (CPU, disk, network, etc.).

du : Estimate file and directory space usage.

dump : Backup a file system to a storage device.

dumpe2fs : Dump ext2/3/4 superblock and block group information.

dumpkeys : Dump the keyboard translation table.

E

echo : Output the given string(s) to standard output.

ed : Classic line‑oriented text editor.

egrep : Grep with extended regular expressions.

eject : Eject removable media (CD‑ROM, floppy, etc.).

emacs : Extensible, self‑documenting text editor.

enable : Enable a disabled shell builtin.

env : Run a command in a modified environment or print the environment.

eval : Evaluate arguments as a Bash command.

ex : Line‑oriented mode of the vi editor.

exec : Replace the shell with the specified command.

exit : Exit the current shell session.

expa : Convert tabs to spaces (read from stdin if no file is given).

expect : Automate interactive applications by scripting expected inputs.

export : Mark variables for export to child processes.

expr : Evaluate expressions (arithmetic, string, logical).

F

factor : Print the prime factors of a given integer.

fc : List, edit, or re‑execute commands from the history.

fc-cache : Build fontconfig cache files.

fc-list : List available fonts and styles.

fdisk : Interactive disk partitioning tool.

fg : Bring a background job to the foreground.

fgrep : Fixed‑string grep (search for literal patterns).

file : Determine file type by examining its contents.

find : Search for files and directories matching criteria.

finger : Display information about system users.

fmt : Simple text formatter that rewraps paragraphs.

fold : Wrap each input line to a specified width.

for : Loop over a list of items in a shell script.

free : Show memory and swap usage.

Fun : Draw simple terminal graphics (e.g., fun utility).

function : Define a shell function.

G

g++ : Compile C++ source files (frontend to gcc).

gawk : GNU implementation of awk.

gcc : GNU Compiler Collection for C, C++, Objective‑C, etc.

gdb : GNU Debugger for inspecting and controlling program execution.

getent : Retrieve entries from administrative databases (passwd, group, hosts, etc.).

gpasswd : Administer /etc/group and /etc/gshadow.

grep : Search files for lines matching a regular expression.

groupadd : Create a new user group.

groupdel : Delete an existing group.

groupmod : Modify a group definition.

groups : List groups a user belongs to.

grpck : Verify integrity of /etc/group and /etc/gshadow.

grpconv : Convert to shadow group format.

gs : Ghostscript interpreter for PostScript and PDF.

gunzip : Decompress .gz files.

gzexe : Compress executable files and automatically decompress on execution.

gzip : Compress files using the LZ77 algorithm.

H

halt : Stop all CPU functions and halt the system.

hash : Maintain a hash table of found commands.

hdparm : Get/set hard‑disk parameters (e.g., DMA, acoustic management).

head : Output the first N lines of a file.

help : Show help for shell builtin commands.

hexdump : Display file contents in hexadecimal, octal, or ASCII.

history : List previously executed commands.

host : DNS lookup utility.

hostid : Print the numeric identifier of the host.

hostname : Show or set the system's host name.

hostnamectl : Query and change the system hostname via systemd.

htop : Interactive process viewer with colorized output.

hwclock : Access the hardware real‑time clock.

I

iconv : Convert text from one character encoding to another.

id : Display user and group identity information.

if : Conditional command execution in shell scripts.

ifconfig : Configure network interfaces (deprecated in favor of ip).

iftop : Real‑time network bandwidth monitor.

ifup : Bring a network interface up.

import : Capture a screenshot of an X window (ImageMagick).

info : Browse GNU info documentation.

insmod : Insert a kernel module.

install : Copy files and set attributes (mode, owner, timestamps).

iostat : Report CPU and I/O statistics for devices.

iotop : Display I/O usage per process.

ip : Modern utility for network configuration (addresses, routes, links).

ipcrm : Remove IPC objects (shared memory, semaphores, message queues).

ipcs : List IPC facilities.

iptables : Configure IPv4 packet filtering and NAT tables.

iptables-save : Save current iptables rules to a file.

iwconfig : Configure wireless network interfaces.

J

join : Join lines of two files on a common field.

journalctl : Query systemd journal logs.

K

kill : Send signals to processes (default SIGTERM).

L

last : Show a list of recent logins from /var/log/wtmp.

less : Pager for viewing file contents interactively.

let : Evaluate arithmetic expressions in Bash.

ln : Create hard or symbolic links.

locate : Find files by name using a prebuilt database.

look : Display lines beginning with a given string.

lsblk : List block devices and their attributes.

lshw : Report detailed hardware configuration.

lsmod : Show loaded kernel modules.

lsof : List open files and the processes that opened them.

lsusb : List USB devices.

M

mailq : Display the mail queue.

man : View manual pages for commands.

md5sum : Compute and verify MD5 checksums.

mkdir : Create directories.

modinfo : Show information about a kernel module.

more : Simple pager (less capable than less).

mount : Attach a filesystem to the directory tree.

mpstat : Report per‑processor statistics.

mv : Move or rename files and directories.

N

nc (netcat) : Versatile networking utility for reading/writing across connections.

netstat : Display network connections, routing tables, interface statistics.

nmcli : Command‑line tool for NetworkManager.

nslookup : Query DNS for name resolution information.

O

od : Dump files in octal, hexadecimal, or other formats.

P

passwd : Change a user's password.

paste : Merge lines of files horizontally (tab‑delimited).

pidof : Find the process ID of a running program.

ping : Test network connectivity to a host.

pinky : Lightweight finger alternative.

pmap : Report memory map of a process.

poweroff : Send ACPI signal to power down the system.

printf : Format and print data (more powerful than echo).

ps : Report a snapshot of current processes.

pwd : Print the current working directory.

R

ranlib : Generate an index to the contents of an archive.

rcp : Copy files between remote hosts (deprecated, insecure).

read : Read a line from standard input into a variable.

readelf : Display information about ELF format files.

readlink : Print the target of a symbolic link.

reboot : Restart the system.

rename : Batch rename files using a Perl regular expression.

reset : Reinitialize the terminal.

restore : Restore files from a backup created with dump.

return : Exit a shell function.

rev : Reverse each line of a file.

rm : Remove files, directories, or links.

rmdir : Remove empty directories.

rmmod : Unload a kernel module.

route : Show or manipulate the IP routing table.

rsync : Efficiently synchronize files and directories between hosts.

S

sar : Collect, report, or save system activity information.

scp : Securely copy files over SSH.

screen : Terminal multiplexer for managing multiple sessions.

script : Record a terminal session to a file.

scriptreplay : Replay a script recording.

sdiff : Compare two files side‑by‑side.

sed : Stream editor for filtering and transforming text.

select : Generate a numbered menu in Bash scripts.

seq : Generate a sequence of numbers.

setsid : Run a program in a new session.

shift : Shift positional parameters left.

showkey : Display keycodes as keys are pressed.

shred : Overwrite a file to hide its contents and optionally delete it.

shutdown : Power off or reboot the system safely.

sleep : Delay execution for a specified time.

source : Execute commands from a file in the current shell.

sort : Sort lines of text files.

split : Split a file into pieces.

ssh : Secure Shell for remote login and command execution.

strace : Trace system calls and signals of a program.

stty : Change and print terminal line settings.

sudo : Execute a command with elevated privileges.

sum : Compute checksum and block count of files.

sync : Flush filesystem buffers.

systemctl : Control the systemd system and service manager.

T

tac : Concatenate files in reverse order.

tail : Output the last N lines of a file.

tar : Archive files (create, extract, list).

tee : Duplicate standard input to both standard output and files.

time : Measure execution time of a command.

top : Real‑time view of running processes.

touch : Change file timestamps or create empty files.

tr : Translate or delete characters.

tracepath : Discover the path MTU to a destination.

traceroute : Show the route packets take to a network host.

tree : Recursively list directories in a tree‑like format.

tty : Print the file name of the terminal connected to standard input.

type : Describe how a command name would be interpreted.

U

uname : Print system information.

unexpand : Convert spaces to tabs.

uniq : Report or filter out repeated lines.

unix2dos : Convert Unix line endings to DOS format.

until : Loop while a command exits with a non‑zero status.

uptime : Show how long the system has been running.

useradd : Create a new user account.

usermod : Modify an existing user account.

username : Retrieve the current user's name.

users : List users currently logged in.

userdel : Delete a user account and its files.

V

vi : Classic visual editor (default on many Unix systems).

vmstat : Report virtual memory statistics.

vnstat : Network traffic monitor.

W

w : Show who is logged on and what they are doing.

wall : Write a message to all users' terminals.

watch : Execute a program periodically, showing output fullscreen.

wc : Count lines, words, and bytes in files.

wget : Retrieve files from the web via HTTP/HTTPS/FTP.

whatis : Display a one‑line description of a command.

which : Locate the executable file associated with a command.

while : Loop while a command succeeds.

who : Show who is logged on.

whoami : Print the effective username.

write : Send a message to another user's terminal.

X

xargs : Build and execute command lines from standard input.

xdg-open : Open a file or URL in the user's preferred application.

Y

yes : Output a string repeatedly until killed (default "y").

Z

zdiff : Run diff on gzip‑compressed files.

zdump : Print the current time in a specified time zone.

zgrep : Search inside compressed files.

zip : Package and compress files into a .zip archive.