Essential Linux Command Cheat Sheet for System Administrators

Online Query and Help Commands (2)

man : View command help and dictionary; more complex info via info.

help : Show built‑in Linux command help, e.g., cd.

File and Directory Operations (18)

ls : List directory contents and attributes.

cd : Change the current working directory.

cp : Copy files or directories.

find : Search directories and files.

mkdir : Create directories.

mv : Move or rename files.

pwd : Print the absolute path of the current directory.

rename : Rename files.

rm : Remove one or more files or directories.

rmdir : Remove empty directories.

touch : Create an empty file or update timestamps.

tree : Display directory contents in a tree structure.

basename : Show the file name component.

dirname : Show the directory component of a path.

chattr : Change file extended attributes.

lsattr : List file extended attributes.

file : Identify the file type.

md5sum : Compute and verify a file's MD5 checksum.

File Content Viewing and Processing (21)

cat : Concatenate and display file contents.

tac : Reverse cat output (display file backwards).

more : Paginate file output.

less : Paginate file output (inverse of more).

head : Show the beginning of a file.

tail : Show the end of a file.

cut : Split lines by a delimiter and output selected fields.

split : Divide a file into smaller pieces.

paste : Merge lines from multiple files.

sort : Sort text lines.

uniq : Remove duplicate lines.

wc : Count lines, words, or bytes.

iconv : Convert file encoding.

dos2unix : Convert DOS line endings to UNIX.

diff : Show differences between files.

vimdiff : Visual file comparison using Vim.

rev : Reverse the characters in each line.

grep/egrep : Filter lines matching patterns.

join : Join files on a common field.

tr : Translate or delete characters.

vi/vim : Command‑line text editor.

Compression and Decompression (4)

tar : Archive and compress files.

unzip : Extract ZIP archives.

gzip : Compress files using gzip.

zip : Create ZIP archives.

System Information Commands (11)

uname : Display OS information.

hostname : Show or set the system hostname.

dmesg : Show boot messages for diagnostics.

uptime : Show system uptime and load.

stat : Show file or filesystem status.

du : Estimate disk usage of files/directories.

df : Report filesystem disk space usage.

top : Real‑time display of system resource usage.

free : Show memory usage.

date : Display or set system date/time.

cal : Show a calendar.

File Search Commands (4)

which : Locate a binary in $PATH.

find : Search the filesystem for files or directories.

whereis : Locate binaries, sources, and manuals.

locate : Search a prebuilt database for file names.

User Management Commands (10)

useradd : Add a new user.

usermod : Modify an existing user.

userdel : Delete a user.

groupadd : Add a new group.

passwd : Change a user's password.

chage : Change password expiry information.

id : Show a user's UID, GID, and groups.

su : Switch user identity.

visudo : Safely edit the sudoers file.

sudo : Execute a command with elevated privileges.

Basic Network Operations (11)

telnet : Remote login using the TELNET protocol.

ssh : Secure remote login via SSH.

scp : Securely copy files between hosts.

wget : Download files from the command line.

ping : Test network connectivity.

route : View or set the routing table.

ifconfig : View and configure network interfaces.

ifup : Bring a network interface up.

ifdown : Bring a network interface down.

netstat : Display network connections.

ss : Show socket statistics.

Advanced Network Operations (9)

nmap : Network scanning.

lsof : List open files.

mail : Send and receive email.

mutt : Email client.

nslookup : Query DNS servers interactively.

dig : Perform DNS lookups.

host : DNS query utility.

traceroute : Trace the route packets take.

tcpdump : Capture network packets.

Disk and Filesystem Commands (16)

mount : Mount a filesystem.

umount : Unmount a filesystem.

fsck : Check and repair filesystems.

dd : Convert and copy files.

dumpe2fs : Dump ext2/3/4 filesystem info.

dump : Backup ext2/3/4 filesystems.

fdisk : Partition disks (up to 2 TB).

parted : Partition disks without size limit.

mkfs : Create a filesystem.

partprobe : Inform the kernel of partition table changes.

e2fsck : Check ext2/3/4 filesystems.

mkswap : Create a swap area.

swapon : Enable swap.

swapoff : Disable swap.

sync : Flush filesystem buffers.

resize2fs : Resize ext2/3/4 filesystems.

System Permissions and Ownership (4)

chmod : Change file or directory permissions.

chown : Change file owner and group.

chgrp : Change group ownership.

umask : Show or set the default permission mask.

User Login Information Commands (7)

whoami : Show the effective username.

who : List logged‑in users.

w : Show logged‑in users and their activities.

last : Display recent login sessions.

lastlog : Show the most recent login of all users.

users : List all logged‑in users.

finger : Display detailed user information.

Built‑in and Miscellaneous Commands (19)

echo : Print text or variable values.

printf : Format and output data.

rpm : Manage RPM packages.

yum : Automate RPM package management.

watch : Repeatedly run a command and display output.

alias : Define command aliases.

unalias : Remove command aliases.

date : View or set system date/time.

clear : Clear the terminal screen.

history : Show command history.

eject : Eject removable media.

time : Measure command execution time.

nc : Powerful networking utility.

xargs : Build command lines from standard input.

exec : Replace the shell with a command.

export : Set or display environment variables.

unset : Remove variables or functions.

type : Determine if a command is built‑in.

bc : Command‑line calculator.

System Management and Performance Monitoring (9)

chkconfig : Manage system startup services.

vmstat : Report virtual memory statistics.

mpstat : Show CPU statistics.

iostat : Report I/O statistics.

sar : Collect comprehensive performance data.

ipcs : Report inter‑process communication facilities.

ipcrm : Remove IPC objects.

strace : Trace system calls and signals.

ltrace : Trace library calls.

Shutdown, Reboot, Logout and System Info (6)

shutdown : Shut down the system.

halt : Halt the system.

poweroff : Power off the machine.

logout : Exit the current shell.

exit : Exit the current shell.

Ctrl+d : Shortcut to exit the shell.

Process Management Commands (15)

bg : Resume a stopped job in the background.

fg : Bring a background job to the foreground.

jobs : List current background jobs.

kill : Terminate a process.

killall : Kill processes by name.

pkill : Kill processes by name using patterns.

crontab : Manage scheduled tasks.

ps : Snapshot of current processes.

pstree : Display processes as a tree.

nice/renice : Adjust process priority.

nohup : Run a command immune to hangups.

pgrep : Search for processes matching criteria.

runlevel : Show the current runlevel.

init : Change the system runlevel.

service : Start, stop, restart, or query system services.