Essential Linux Command Cheat Sheet: 200+ Commands Every Sysadmin Should Know

Online Query and Help Commands (2)

man

– View command manuals and detailed help. help – Show built‑in Bash help for commands like cd.

File and Directory Operations (18)

ls

– List directory contents with attributes. cd – Change the current working directory. cp – Copy files or directories. find – Search for files or directories. mkdir – Create a new directory. 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 view. basename – Strip directory path, leaving only the file name. dirname – Show the directory portion of a path. chattr – Change file extended attributes. lsattr – List file extended attributes. file – Identify the type of a file. 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 – Paginate output. less – Paginate output with backward navigation. head – Show the beginning of a file. tail – Show the end of a file. cut – Split lines by delimiter and output selected fields. split – Divide a file into smaller pieces. paste – Merge lines of files side by side. sort – Sort text lines. uniq – Remove duplicate adjacent 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 side‑by‑side diff in Vim. rev – Reverse each line of a file. grep / egrep – Search for patterns in text. join – Join two files on a common field. tr – Translate or delete characters. vi / vim – Command‑line text editors.

File Compression and Extraction (4)

tar

– Archive files; optionally compress. unzip – Extract ZIP archives. gzip – Compress or decompress files using gzip. zip – Create ZIP archives.

System Information Commands (11)

uname

– Display kernel and OS information. hostname – Show or set the system hostname. dmesg – Print kernel ring buffer messages (boot info). uptime – Show how long the system has been running and load average. stat – Show detailed file or filesystem status. du – Estimate disk usage of files/directories. df – Report filesystem space usage. top – Real‑time view of processes and resource usage. free – Display memory usage. date – Show or set the system date/time. cal – Display a calendar.

File Search Commands (4)

which

– Locate an executable in the PATH. find – Search the filesystem hierarchy for files. whereis – Locate binary, source, and manual page files. locate – Find files using a prebuilt database; update with updatedb.

User Management Commands (10)

useradd

– Add a new user. usermod – Modify an existing user’s attributes. userdel – Delete a user. groupadd – Create 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 – Safely edit the /etc/sudoers file. sudo – Execute a command as another user (default root) per sudoers policy.

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 web. ping – Test network connectivity to a host. route – Show or modify the kernel routing table. ifconfig – Configure network interfaces. ifup – Bring a network interface up. ifdown – Bring a network interface down. netstat – Display network connections, routing tables, and interface statistics. ss – Modern utility to dump socket statistics.

Advanced Network Operations (9)

nmap

– Network scanner. lsof – List open files and the processes using them. mail – Send and receive email. mutt – Text‑based email client. nslookup – Interactive DNS query tool. dig – DNS lookup utility. host – Simple DNS query. traceroute – Trace the route packets take to a network host. tcpdump – Command‑line packet capture tool.

Disk and Filesystem Commands (16)

mount

– Mount a filesystem. umount – Unmount a filesystem. fsck – Check and repair Linux filesystems. dd – Convert and copy files, often for low‑level backups. dumpe2fs – Dump ext2/3/4 filesystem information. dump – Backup ext2/3/4 filesystems. fdisk – Partition disks up to 2 TB. parted – Partition disks without size limits. mkfs – Create a new filesystem. partprobe – Inform the kernel of partition table changes. e2fsck – Check ext2/3/4 filesystems. mkswap – Set up a swap area. swapon – Enable a swap area. swapoff – Disable a swap area. sync – Flush filesystem buffers to disk. resize2fs – Resize ext2/3/4 filesystems.

System Permissions and Authorization (4)

chmod

– Change file or directory permissions. chown – Change file owner and group. chgrp – Change group ownership. umask – Set default permission mask for new files.

Login and User Session Information (7)

whoami

– Print the effective username. who – List users currently logged in. w – Show who is logged in and what they are doing. last – Display a list of recent logins. lastlog – Show the most recent login of all users. users – Print the usernames of users currently logged in. finger – Retrieve information about users.

Built‑in Shell Commands and Miscellaneous (19)

echo

– Print text or variable values. printf – Format and print data. rpm – Manage RPM packages. yum – High‑level package manager for RPM‑based systems. watch – Execute a command periodically and display the output. alias – Define a shortcut for a command. unalias – Remove a command alias. type – Determine how a command would be interpreted. bc – Command‑line calculator.

System Management and Performance Monitoring (9)

chkconfig

– Manage system services at boot. vmstat – Report virtual memory statistics. mpstat – Show CPU usage per processor. iostat – Report I/O statistics. sar – Collect, report, or save system activity information. ipcs – Report inter‑process communication facilities. ipcrm – Remove IPC objects. strace – Trace system calls and signals of a process. ltrace – Trace library calls made by a process.

Shutdown, Reboot, and Logout Commands (6)

shutdown

– Power off or reboot the system. halt – Halt the system. poweroff – Turn off the power. logout – Exit the current shell session. exit – Exit the current shell session. 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 jobs. kill – Send a signal to terminate a process. killall – Kill processes by name. pkill – Kill processes by name using patterns. crontab – Schedule recurring tasks. ps – Snapshot of current processes. pstree – Tree view of processes. nice / renice – Adjust process priority. nohup – Run a command immune to hangups. pgrep – Search for processes matching criteria. runlevel – Show the current system runlevel. init – Change the system runlevel. service – Start, stop, restart, or query system services.