Essential Linux Command Cheat Sheet: Master System Operations

This article provides a detailed reference of frequently used Linux commands, organized by functional categories. Each entry includes the command name and a brief English description of its purpose.

Help Commands (2)

man

– View command help pages and dictionaries; more complex information can be accessed with info. help – Show built‑in command help for commands such as 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 for files and directories. mkdir – Create a new directory. mv – Move or rename files. pwd – Print the absolute path of the current directory. rename – Rename a file. 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 of a path. dirname – Show the directory component of a path. chattr – Change file attributes. lsattr – List file attributes. file – Determine the file type. md5sum – Compute and verify an MD5 checksum.

Viewing and Processing File Content (21)

cat

– Concatenate and display file contents. tac – Display file contents in reverse order. more – Page through file contents. less – Page through file contents (alternative to 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 – Compare file differences. vimdiff – Visual file comparison using Vim. rev – Reverse the order of characters in each line. grep / egrep – Filter lines matching a pattern. join – Join two files on a common field. tr – Translate or delete characters. vi / vim – Text editors for the command line.

File Compression and Extraction (4)

tar

– Archive and compress files. unzip – Extract ZIP archives. gzip – Compress files using gzip. zip – Create ZIP archives.

System Information Commands (11)

uname

– Show OS information. hostname – Display or set the system hostname. dmesg – Show kernel boot messages. uptime – Show system uptime and load. stat – Display 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 the system date/time. cal – Show a calendar.

Network Operations (Basic 11, Advanced 9)

telnet

– Remote login using the Telnet protocol. ssh – Secure remote login. scp – Secure copy between hosts. wget – Download files from the web. ping – Test network connectivity. route – View or set routing tables. ifconfig – Configure network interfaces. ifup – Bring a network interface up. ifdown – Bring a network interface down. netstat – Display network connections and routing tables. ss – Show socket statistics. nmap – Network scanning tool. lsof – List open files. mail – Send and receive email. mutt – Command‑line email client. nslookup – Query DNS servers interactively. dig – Perform DNS lookups. host – DNS query utility. traceroute – Trace the route packets take to a host. tcpdump – Capture network packets.

User Management (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 user and group IDs. su – Switch user identity. visudo – Edit the /etc/sudoers file safely. sudo – Execute a command as another user (default root) according to sudoers rules.

Permission 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.

Process Management (15)

bg

– Resume a suspended job in the background. fg – Bring a background job to the foreground. jobs – List current background jobs. kill – Terminate a process by PID. killall – Terminate processes by name. pkill – Kill processes matching a pattern. crontab – Manage scheduled tasks. ps – Snapshot of current processes. pstree – Display processes in a tree view. nice / renice – Adjust process priority. nohup – Run a command immune to hangups. pgrep – Find processes matching criteria. runlevel – Show the current system runlevel. init – Change the system runlevel. service – Start, stop, restart, or query system services.

System Monitoring and Performance (9)

chkconfig

– Manage system startup services. vmstat – Virtual memory statistics. mpstat – CPU usage statistics. iostat – I/O statistics. sar – Collect comprehensive performance data. ipcs – Report inter‑process communication facilities. ipcrm – Remove IPC objects. strace – Trace system calls and signals of a process. ltrace – Trace library function calls of a process.

Shutdown, Reboot, Logout and System Info (6)

shutdown

– Power off the system. halt – Halt the system. poweroff – Turn off power. logout – Exit the current shell session. exit – Exit the current shell session. Ctrl+d – Shortcut to exit the shell.

Miscellaneous Built‑in Commands (19)

echo

– Print text or variable values. printf – Formatted output. rpm – Manage RPM packages. yum – Simplified RPM package management. watch – Repeatedly execute a command and display output. alias – Define command aliases. unalias – Remove command aliases. clear – Clear the terminal screen. history – Show command history. eject – Eject optical media. time – Measure execution time of a command. nc – Powerful network utility (netcat). xargs – Build command lines from standard input. exec – Replace the shell with a specified command. export – Set or display environment variables. unset – Remove variables or functions. type – Determine if a command is built‑in. bc – Command‑line calculator.

This reference serves as a quick lookup for Linux users who need to perform everyday system administration tasks efficiently.