Linux Commands A-Z Index: 180+ Commands with Links to Why, What and How

By Ravindra Bagale, trainer LinkedIn Last updated: 26 October 2026

This page is the master index of the Linux Commands A-Z reference. It lists 183 commands, from alias to zip, with a one-line meaning and a link to the section that explains why you need it, what it is and how to use it, with step-by-step examples. Commands already explained in depth in earlier chapters link straight to those sections. The rest are published in eight A-Z parts. Use the letter bar to jump.

What you'll learn in this chapter

Find any Linux command in seconds by letter
Know what each command does in one line
Jump to its full why, what and how section
Pick the right command for a job using the task map
Find commands you do not know with apropos, man -k and type
Plan your learning across the eight A-Z parts

1. An everyday example: the index at the back of a textbook

Why do we need this?

When Sai studies for his engineering exam at Fergusson College, he never reads the whole book to find "Ohm's law". He turns to the index at the back, finds O, and goes straight to page 214.

What is it?

This page is that index for Linux. Each letter is a heading, each row is a command, and the Where column is the page number: a link to the exact section.

How to do it (step by step)

If you do not know the name, start with the task map below.

2. The eight A-Z parts

Why do we need this?

A single page with 183 full commands would be too slow and too long to study.

What is it?

The commands are split into eight parts of about 20 to 24 each. 13 commands already had full sections in earlier chapters and are linked, not repeated.

Part	Range	Status
Part 1	alias to chown	Published
Part 2	chronyc to du	Published
Part 3	echo to host	Published
Part 4	hostname to lvcreate	Published
Part 5	man to read	Published
Part 6	reboot to stat	Published
Part 7	strace to uname	Coming next
Part 8	uniq to zip	Coming next

How to do it (step by step)

Count how many commands your system has.

compgen -c | sort -u | wc -l

Output:

What it means: Thousands exist, but about 180 cover almost all daily admin work.

Check where a command comes from.

type -a ls; rpm -qf /usr/bin/ls

Output:

ls is aliased to `ls --color=auto'
ls is /usr/bin/ls
coreutils-8.32-35.el9.x86_64

What it means: ls is an alias for a program from the coreutils package.

3. Task map: which command for which job

Why do we need this?

Most of the time you know the job, not the command name.

What is it?

This map groups commands by the job they do. Each one is in the A-Z list below.

Job	Commands
Files and folders	ls cd cp mv rm mkdir find stat ln
Read and filter text	cat less head tail grep sed awk cut sort uniq wc tr
Users and permissions	useradd passwd chage chmod chown chgrp sudo id
Processes and services	ps top kill nice systemctl journalctl
Disk and storage	df du lsblk blkid mount fdisk lvcreate
Network	ip ss ping dig curl wget nc traceroute
Packages	apt dnf rpm
Archive and compress	tar gzip bzip2 xz zip
Schedule	crontab at systemctl list-timers

How to do it (step by step)

Find a command by a keyword.

apropos -s 1,8 "disk usage"

Output:

df (1)  - report file system space usage
du (1)  - estimate file space usage

What it means: Now look up df or du below.

4. Linux Commands A-Z list

Why do we need this?

One list, every command, one click to the details.

What is it?

Rows marked Coming next will become links when that part is published.

How to do it (step by step)

Jump to a letter: A B C D E F G H I J K L M N P R S T U V W X Y Z

A

Command	What it does	Where
`alias`	Make a short name for a long command	A-Z Part 1
`apropos`	Search man pages by keyword	A-Z Part 1
`apt`	Install packages on Debian and Ubuntu	A-Z Part 1
`at`	Run a command once at a later time	A-Z Part 1
`awk`	Work with columns, sums and reports in text	A-Z Part 1

B

Command	What it does	Where
`base64`	Encode or decode data as base64 text	A-Z Part 1
`basename`	Get the file name from a path	A-Z Part 1
`bc`	Calculator with decimals	A-Z Part 1
`bg`	Resume a stopped job in the background	A-Z Part 1
`blkid`	Show UUID and type of disks and partitions	A-Z Part 1
`bunzip2`	Uncompress .bz2 files	A-Z Part 1
`bzip2`	Compress files with bzip2	A-Z Part 1

C

Command	What it does	Where
`cal`	Show a calendar	A-Z Part 1
`cat`	Print and join files	A-Z Part 1
`cd`	Change the current folder	Full section (earlier chapter)
`chage`	Set password ageing rules	A-Z Part 1
`chattr`	Set special file attributes like immutable	A-Z Part 1
`chgrp`	Change the group of a file	A-Z Part 1
`chmod`	Change file permissions	Full section (earlier chapter)
`chown`	Change file owner and group	Full section (earlier chapter)
`chronyc`	Check and control time sync	A-Z Part 2
`chroot`	Run a shell inside another root folder	A-Z Part 2
`cksum`	Print a CRC checksum and size	A-Z Part 2
`clear`	Clear the terminal screen	A-Z Part 2
`cmp`	Compare two files byte by byte	A-Z Part 2
`column`	Format text into neat columns	A-Z Part 2
`comm`	Compare two sorted files line by line	A-Z Part 2
`cp`	Copy files and folders	Full section (earlier chapter)
`crontab`	Schedule repeating jobs	A-Z Part 2
`curl`	Talk to web servers and APIs	A-Z Part 2
`cut`	Cut columns or characters from lines	A-Z Part 2

D

Command	What it does	Where
`date`	Show or format date and time	A-Z Part 2
`dd`	Copy raw data block by block	A-Z Part 2
`df`	Show free disk space per filesystem	A-Z Part 2
`diff`	Show differences between files	A-Z Part 2
`dig`	Query DNS records	A-Z Part 2
`dirname`	Get the folder part of a path	A-Z Part 2
`dmesg`	Read kernel messages	A-Z Part 2
`dnf`	Install packages on RHEL, Fedora, Amazon Linux	A-Z Part 2
`du`	Show how much space folders use	A-Z Part 2

E

Command	What it does	Where
`echo`	Print text	A-Z Part 3
`env`	Show or set environment for a command	A-Z Part 3
`exit`	Leave a shell with a status code	A-Z Part 3
`export`	Make a variable visible to child programs	A-Z Part 3
`expr`	Simple maths and string checks	A-Z Part 3

F

Command	What it does	Where
`fdisk`	Create and list disk partitions	A-Z Part 3
`fg`	Bring a job to the foreground	A-Z Part 3
`file`	Detect what kind of file it is	A-Z Part 3
`find`	Search files by name, size, time	A-Z Part 3
`firewall-cmd`	Manage firewalld rules	A-Z Part 3
`free`	Show memory and swap use	A-Z Part 3
`fsck`	Check and repair a filesystem	A-Z Part 3
`fuser`	Show which process uses a file or port	A-Z Part 3

G

Command	What it does	Where
`getent`	Look up users, groups, hosts	A-Z Part 3
`getfacl`	Show ACL permissions	A-Z Part 3
`grep`	Search text for patterns	A-Z Part 3
`groupadd`	Create a group	A-Z Part 3
`groups`	Show groups of a user	A-Z Part 3
`gunzip`	Uncompress .gz files	A-Z Part 3
`gzip`	Compress files with gzip	A-Z Part 3

H

Command	What it does	Where
`halt`	Stop the system	A-Z Part 3
`head`	Show the first lines	A-Z Part 3
`history`	Show past commands	A-Z Part 3
`host`	Simple DNS lookup	A-Z Part 3
`hostname`	Show or set the host name	A-Z Part 4
`hostnamectl`	Manage host name with systemd	A-Z Part 4
`htop`	Interactive process viewer	A-Z Part 4

I

Command	What it does	Where
`id`	Show user and group ids	A-Z Part 4
`ifconfig`	Old tool to show network interfaces	A-Z Part 4
`iostat`	Show disk I/O stats	A-Z Part 4
`ip`	Show and set addresses and routes	A-Z Part 4
`iptables`	Low-level firewall rules	A-Z Part 4

J

Command	What it does	Where
`jobs`	List shell jobs	A-Z Part 4
`journalctl`	Read systemd logs	A-Z Part 4
`jq`	Read and filter JSON	A-Z Part 4

K

Command	What it does	Where
`kill`	Send a signal to a process	A-Z Part 4
`killall`	Signal processes by name	A-Z Part 4

L

Command	What it does	Where
`last`	Show login history	A-Z Part 4
`less`	Page through a file	A-Z Part 4
`ln`	Create hard and soft links	A-Z Part 4
`locate`	Find files fast from a database	A-Z Part 4
`logger`	Write a message to the system log	A-Z Part 4
`logrotate`	Rotate and compress logs	A-Z Part 4
`ls`	List files	A-Z Part 4
`lsblk`	List block devices	A-Z Part 4
`lscpu`	Show CPU details	A-Z Part 4
`lsof`	List open files	A-Z Part 4
`lvcreate`	Create an LVM logical volume	A-Z Part 4

M

Command	What it does	Where
`man`	Read the manual	A-Z Part 5
`md5sum`	MD5 checksum	A-Z Part 5
`mkdir`	Create folders	Full section (earlier chapter)
`mkfs`	Create a filesystem	A-Z Part 5
`mktemp`	Create a safe temp file or folder	A-Z Part 5
`more`	Simple pager	A-Z Part 5
`mount`	Attach a filesystem	A-Z Part 5
`mv`	Move or rename	Full section (earlier chapter)

N

Command	What it does	Where
`nc`	Open raw TCP or UDP connections	A-Z Part 5
`netstat`	Old tool for sockets and routes	A-Z Part 5
`nice`	Start a command with lower priority	A-Z Part 5
`nmcli`	Control NetworkManager	A-Z Part 5
`nohup`	Keep a command running after logout	A-Z Part 5
`nslookup`	Simple DNS query	A-Z Part 5

P

Command	What it does	Where
`passwd`	Change a password	A-Z Part 5
`paste`	Join lines side by side	A-Z Part 5
`pgrep`	Find process ids by name	A-Z Part 5
`ping`	Test if a host answers	A-Z Part 5
`pkill`	Signal processes by name or pattern	A-Z Part 5
`printf`	Print formatted text	A-Z Part 5
`ps`	List processes	A-Z Part 5
`pvcreate`	Prepare a disk for LVM	A-Z Part 5
`pwd`	Print the current folder	A-Z Part 5

R

Command	What it does	Where
`read`	Read input into variables	A-Z Part 5
`reboot`	Restart the system	A-Z Part 6
`renice`	Change priority of a running process	A-Z Part 6
`restorecon`	Restore SELinux labels	A-Z Part 6
`rm`	Delete files	Full section (earlier chapter)
`rmdir`	Delete empty folders	Full section (earlier chapter)
`rpm`	Query and install RPM packages	A-Z Part 6
`rsync`	Fast sync of files and folders	A-Z Part 6

S

Command	What it does	Where
`scp`	Copy files over SSH	Full section (earlier chapter)
`screen`	Keep terminal sessions alive	A-Z Part 6
`sed`	Find and replace in text streams	A-Z Part 6
`semanage`	Persistent SELinux settings	A-Z Part 6
`seq`	Print number sequences	A-Z Part 6
`setfacl`	Set ACL permissions	A-Z Part 6
`sestatus`	Show SELinux status	A-Z Part 6
`sha256sum`	SHA-256 checksum	A-Z Part 6
`shutdown`	Power off or reboot safely	A-Z Part 6
`sleep`	Wait for some time	A-Z Part 6
`sort`	Sort lines	A-Z Part 6
`source`	Run a file in the current shell	A-Z Part 6
`split`	Split a big file into parts	A-Z Part 6
`ss`	Show sockets and listening ports	A-Z Part 6
`ssh`	Log in to a remote server	A-Z Part 6
`ssh-keygen`	Create SSH keys	A-Z Part 6
`stat`	Show file details and times	A-Z Part 6
`strace`	Trace system calls	A-Z Part 7 (coming next)
`su`	Switch user	A-Z Part 7 (coming next)
`sudo`	Run a command as another user	A-Z Part 7 (coming next)
`swapon`	Enable and show swap	A-Z Part 7 (coming next)
`sysctl`	Read and set kernel settings	A-Z Part 7 (coming next)
`systemctl`	Manage services	A-Z Part 7 (coming next)

T

Command	What it does	Where
`tail`	Show the last lines or follow a log	A-Z Part 7 (coming next)
`tar`	Pack files into an archive	A-Z Part 7 (coming next)
`tee`	Write output to screen and file	A-Z Part 7 (coming next)
`test`	Check files and values	A-Z Part 7 (coming next)
`time`	Measure how long a command takes	A-Z Part 7 (coming next)
`timedatectl`	Manage time and time zone	A-Z Part 7 (coming next)
`tmux`	Split and keep terminal sessions	A-Z Part 7 (coming next)
`top`	Live view of processes	A-Z Part 7 (coming next)
`touch`	Create empty files or update times	Full section (earlier chapter)
`tr`	Translate or delete characters	A-Z Part 7 (coming next)
`traceroute`	Show the network path to a host	A-Z Part 7 (coming next)
`tree`	Show folders as a tree	A-Z Part 7 (coming next)
`truncate`	Shrink or grow a file to a size	A-Z Part 7 (coming next)
`type`	Show how a command name is resolved	A-Z Part 7 (coming next)

U

Command	What it does	Where
`ulimit`	Show and set user limits	A-Z Part 7 (coming next)
`umask`	Default permission mask	A-Z Part 7 (coming next)
`umount`	Detach a filesystem	A-Z Part 7 (coming next)
`uname`	Show kernel and system info	A-Z Part 7 (coming next)
`uniq`	Remove or count repeated lines	A-Z Part 8 (coming next)
`unzip`	Extract zip files	Full section (earlier chapter)
`uptime`	Show uptime and load	A-Z Part 8 (coming next)
`useradd`	Create a user	A-Z Part 8 (coming next)
`userdel`	Delete a user	A-Z Part 8 (coming next)
`usermod`	Change a user	A-Z Part 8 (coming next)

V

Command	What it does	Where
`vgcreate`	Create an LVM volume group	A-Z Part 8 (coming next)
`vim`	Edit files in the terminal	A-Z Part 8 (coming next)
`vmstat`	Memory, CPU and I/O summary	A-Z Part 8 (coming next)

W

Command	What it does	Where
`w`	Who is logged in and what they do	A-Z Part 8 (coming next)
`watch`	Run a command again and again	A-Z Part 8 (coming next)
`wc`	Count lines, words, bytes	A-Z Part 8 (coming next)
`wget`	Download files	Full section (earlier chapter)
`whereis`	Find binary, source and man page	A-Z Part 8 (coming next)
`which`	Show the path of a command	A-Z Part 8 (coming next)
`who`	Show logged-in users	A-Z Part 8 (coming next)
`whoami`	Print your user name	A-Z Part 8 (coming next)

X

Command	What it does	Where
`xargs`	Build commands from input	A-Z Part 8 (coming next)
`xz`	Compress files with xz	A-Z Part 8 (coming next)

Y

Command	What it does	Where
`yes`	Print a line again and again	A-Z Part 8 (coming next)
`yum`	Old package tool on RHEL and CentOS	A-Z Part 8 (coming next)

Z

Command	What it does	Where
`zcat`	Read .gz files without unpacking	A-Z Part 8 (coming next)
`zip`	Create zip files	Full section (earlier chapter)

5. Real examples from many industries

Why do we need this?

The same Linux skill shows up in every kind of company. Seeing it in many places helps you remember it.

What is it?

Each row is a made-up team. It shows who uses this and how.

How to do it (step by step)

Team and city	How they use it	Command
Asha, fresher, Hinjewadi	Uses the index to revise before interviews	`apropos network`
Vikram, bank ops, Pune	Shares #cmd links in runbooks	`man -k cron`
Farah, hospital IT, Erandwane	Looks up rarely used commands like chage	`type -a chage`
Deepak, SaaS, Baner	Finds which package gives a missing command	`dnf provides */bin/dig`
Prachi, college lab, Ganeshkhind	Gives students the letter list as homework	`compgen -c \| grep ^ch`
Rohan, cloud, Viman Nagar	Checks if a name is alias or binary	`type ll`

6. Common errors and how to fix them

Why do we need this?

Everyone hits these errors. Knowing the cause saves hours.

What is it?

Read the exact message first. Then match it to a row below.

How to do it (step by step)

Error you see	Why it happens	How to fix
`bash: dig: command not found`	Package not installed	Find and install it. `dnf provides */bin/dig`
`No manual entry for chronyc`	man page package missing	Install man pages. `dnf install -y man-pages man-db`
`nothing appropriate.`	mandb not built	Build it. `mandb`
`ls: unrecognized option '--colour=always' (on macOS)`	BSD tools differ from GNU	Use GNU coreutils or check man. `man ls`
`sudo: crontab: command not found`	sudo uses a secure PATH	Use the full path. `sudo /usr/bin/crontab -l`
`-bash: ll: command not found`	ll is an alias, not a program	Define it. `alias ll='ls -l'`
`Permission denied when running ./tool`	No execute bit	Add it. `chmod +x tool`
`command not found after install`	Shell cached the old PATH lookup	Clear the hash. `hash -r`
`which: no xyz in (/usr/bin:...)`	Not in PATH	Check PATH or use full path. `echo $PATH`

7. Troubleshooting step by step

Why do we need this?

When you cannot find or run a command, check in this order.

What is it?

Go top to bottom. Stop at the first step that shows the problem.

How to do it (step by step)

Is it a builtin, alias or file?

type -a name

Is it in PATH?

command -v name || echo missing

Which package provides it?

dnf provides */bin/name

Is a man page there?

man -w name

Search by keyword.

apropos keyword

Clear the shell cache.

hash -r

8. Lab 1: Build your own command list

Why do we need this?

List all commands on your system, keep those in this index and see which you have not used yet.

What is it?

A full hands-on lab. Run every step on a test Linux machine (an EC2 instance, a VM, or WSL).

How to do it (step by step)

All commands.

compgen -c | sort -u > all.txt; wc -l < all.txt

Output:

Your history.

history | awk '{print $2}' | sort -u > used.txt; wc -l < used.txt

Output:

Save the A-Z list (copy the names from the table).

nano az.txt

Commands in A-Z you have never used.

comm -23 <(sort az.txt) used.txt | head

Output:

apropos
at
bc

Which of them are installed?

for c in $(comm -23 <(sort az.txt) used.txt); do command -v $c >/dev/null && echo $c; done | head -3

Output:

apropos
at
bc

Pick five and open their sections.

9. Lab 2: Find the right tool for five jobs

Why do we need this?

Use only apropos, man -k and this index to find the command for five jobs.

What is it?

A full hands-on lab. Run every step on a test Linux machine (an EC2 instance, a VM, or WSL).

How to do it (step by step)

Change a password expiry.

apropos -s 1,8 "password expiry"

Output:

chage (1) - change user password expiry information

Compare two sorted files.

apropos "compare two sorted"

Output:

comm (1) - compare two sorted files line by line

Show kernel messages.

apropos -s 1 kernel | grep -i ring

Output:

dmesg (1) - print or control the kernel ring buffer

Find block device UUIDs.

apropos -s 8 "block device attributes"

Output:

blkid (8) - locate/print block device attributes

Encode to base64.

apropos base64 | head -1

Output:

base64 (1) - base64 encode/decode data and print to standard output

Ravindra Bagale's Tip

Bookmark this page. When you meet a command at work, find it here, open its section, and run one example on a test machine that same day. One command a day is 180 commands in six months.

10. Frequently asked questions

Q. Is this every Linux command?

No. Linux has thousands. This is the 183 most useful for admin, DevOps and cloud jobs.

Q. Why do some rows say Coming next?

That part is not published yet. The row becomes a link when it is.

Q. Where are grep, sed and awk?

awk is in Part 1 with a deep dive. grep is in Part 3 and sed in Part 6, both as deep dives.

Q. Do commands work the same on Ubuntu and RHEL?

Mostly. Package tools differ (apt vs dnf) and a few options differ.

Q. Does it work on macOS?

Many commands exist but use BSD options. Check man on the Mac.

Q. How should I study?

One part per week, every example run by hand, then the tasks.

Q. Can I link one command?

Yes. Every section has an anchor like #cmd-awk.

Q. Is there a quiz?

Yes, at the end of every part including this one.

11. Interview questions and answers

Beginner level

Q. How do you find a command whose name you forgot?

apropos keyword or man -k keyword.

Q. What does type do?

Tells if a name is an alias, builtin, function or file.

Q. How do you see a command's options quickly?

command --help.

Q. What are man sections 1 and 8?

1 user commands, 8 admin commands.

Mid level level

Q. Command not found but the package is installed. Why?

Not in PATH, sudo secure_path, or hash cache. Check command -v and hash -r.

Q. How do you find which package owns a file?

rpm -qf or dpkg -S; dnf provides for missing ones.

Q. builtin vs external command?

Builtins run inside the shell (cd, alias); external ones are files in PATH.

Q. Why might ls behave differently on two servers?

Aliases, GNU vs BSD, or version differences.

Senior level

Q. How would you standardise tools across 500 servers?

A base package list in config management, version pinning, and a check job that compares command -v output.

Q. Which 10 commands would you teach a new on-call engineer first?

df, du, free, top, ps, ss, journalctl, systemctl, curl, dig.

Q. How do you check a command is safe before running it from a blog?

Read man, run with --help or a dry run, test in a VM, never pipe curl to sudo bash.

Try at home

Pick one letter a day and read every one-liner under it.
Run type -a on ten commands from the list and note which are aliases or builtins.
Use apropos to find three commands not in this list and read their man pages.

Practice Tasks

About this scenario

Maple Leaf Books is a bookselling business in Toronto. Emily Tremblay looks after its IT and cloud work. They count money in CAD and run their AWS resources in the ca-central-1 Region. In the tasks below you do real jobs for them using what this lesson teaches. All names, account IDs, IP addresses and numbers are made up for practice.

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