A comprehensive, well-structured, and categorized repository containing over 100 essential Linux commands. Whether you are a system administrator, a DevOps engineer, or a cybersecurity professional, this quick-reference guide has got you covered[cite: 1].
ls— Lists all files and directories in the present working directory[cite: 1].ls -R— Lists files in sub-directories as well[cite: 1].ls -a— Shows hidden files[cite: 1].ls -al— Lists files and directories with detailed information (permissions, size, owner, etc.)[cite: 1].cd directoryname— Changes the current directory[cite: 1].cd ..— Moves one level up in the directory tree[cite: 1].pwd— Displays the present working directory path[cite: 1].cat > filename— Creates a new file quickly[cite: 1].cat filename— Displays the contents of a file[cite: 1].cat file1 file2 > file3— Joins two files and stores the output in a new file[cite: 1].touch filename— Creates an empty file or modifies file timestamps[cite: 1].rm filename— Deletes a specific file[cite: 1].cp source destination— Copies files from source to destination path[cite: 1].mv source destination— Moves or renames files[cite: 1].find / -name filename— Finds a file or directory starting from the root directory[cite: 1].file filename— Determines the file type[cite: 1].less filename— Views the file content interactively page by page[cite: 1].head filename— Views the first ten lines of a file[cite: 1].tail filename— Views the last ten lines of a file[cite: 1].lsof— Shows which files are opened by which running processes[cite: 1].du -h --max-depth=1— Shows the size of directories up to current depth[cite: 1].fdisk— Disk partition manipulation utility[cite: 1].
mkdir directoryname— Creates a new directory[cite: 1].rmdir directoryname— Deletes an empty directory[cite: 1].cp -r source destination— Copies directories recursively[cite: 1].mv olddir newdir— Renames or moves directories[cite: 1].find / -type d -name directoryname— Finds a specific directory starting from root[cite: 1].
ps— Displays your currently active processes[cite: 1].top— Displays all running system processes in real-time[cite: 1].htop— An interactive, user-friendly process viewer (Modern alternative totop)[cite: 1].kill pid— Kills a process using its Process ID (PID)[cite: 1].pkill name— Kills a process by its name[cite: 1].bg— Resumes suspended jobs without bringing them to the foreground[cite: 1].fg— Brings the most recent background job to the foreground[cite: 1].fg n— Brings a specific jobnto the foreground[cite: 1].renice +n [pid]— Changes the priority of a running process[cite: 1].&>filename— Redirects both stdout and stderr to a file[cite: 1].1>filename— Redirects only standard output (stdout) to a file[cite: 1].2>filename— Redirects only standard error (stderr) to a file[cite: 1].
chmod octal filename— Changes file permissions using octal values (e.g.,755,644)[cite: 1].chown ownername filename— Changes the owner of a file[cite: 1].chgrp groupname filename— Changes the group ownership of a file[cite: 1].
ping host— Pings a host to check network connectivity and outputs results[cite: 1].whois domain— Retrieves WHOIS information for a specific domain[cite: 1].dig domain— Gathers DNS details and information for a domain[cite: 1].netstat -pnltu— Displays active network connections, routing tables, and interface stats[cite: 1].ss— Investigates sockets (A modern, faster alternative tonetstat)[cite: 1].ifconfig— Displays IP addresses and configurations of network interfaces[cite: 1].ssh user@host— Securely logs into a remote host as a specified user[cite: 1].scp— Securely transfers files between hosts over an SSH connection[cite: 1].wget url— Downloads files directly from the web[cite: 1].curl url— Sends a request to a URL and returns the server's response[cite: 1].traceroute domain— Prints the path/route that packets take to reach a destination domain[cite: 1].mtr domain— Combinestracerouteandpingfunctionalities into one diagnostic tool[cite: 1].nmap— Advanced network exploration tool and security scanner[cite: 1].
tar -cvf archive.tar dirname/— Creates a new tar archive from a directory[cite: 1].tar xvf archive.tar— Extracts files from a standard.tararchive[cite: 1].tar -jcvf archive.tar.bz2 dirname/— Creates a highly compressed.bz2archive[cite: 1].tar -jxvf archive.tar.bz2— Extracts files from a.bz2compressed archive[cite: 1].gzip file— Compresses a file and automatically renames it tofile.gz[cite: 1].gzip -d file.gz— Decompresses a.gzfile back to its original state[cite: 1].zip -r file.zip files— Creates a standard.zipcompressed archive[cite: 1].unzip file.zip— Extracts the contents of a.ziparchive file[cite: 1].
grep pattern files— Searches for a specific pattern inside files[cite: 1].grep -r pattern dir— Recursively searches for a pattern within a directory[cite: 1].command | grep pattern— Pipes the output of any command togrepfor filtering[cite: 1].echo 'text'— Prints the specified text line to the terminal[cite: 1].sed 's/string1/string2/g' filename— Replacesstring1withstring2globally inside a file[cite: 1].sed -i 's/string1/string2/g' filename— Replaces strings and saves changes directly in-place[cite: 1].diff file1 file2— Compares two text files and displays the structural differences[cite: 1].wc filename— Counts lines, words, and total characters within a file[cite: 1].awk— A highly versatile pattern-scanning and processing programming language[cite: 1].cut -d':' -f1 /etc/passwd— Extracts specific fields from a line using a delimiter[cite: 1].
df -h— Shows available disk space in human-readable formats (GB/MB)[cite: 1].du -sh— Shows the summary of disk space used by the current directory[cite: 1].free -m— Shows free and used physical memory (RAM) and swap space in MB[cite: 1].whereis app— Locates the binary, source, and manual page files for an application[cite: 1].
date— Displays the current system date and time[cite: 1].cal— Displays the current month's calendar overview[cite: 1].uptime— Shows how long the system has been continuously running[cite: 1].w— Displays structural data about who is currently logged online[cite: 1].whoami— Prints the exact username you are logged in as[cite: 1].uname -a— Shows comprehensive system kernel and architecture information[cite: 1].
sudo apt-get update— Updates local package indexes for available upgrades[cite: 1].sudo apt-get upgrade— Upgrades all upgradable system packages safely[cite: 1].sudo apt-get install pkgname— Installs a specified package via APT repository[cite: 1].sudo apt-get remove pkgname— Uninstalls a package while leaving configuration files[cite: 1].pip install packagename— Installs a Python package from PyPI[cite: 1].pip uninstall packagename— Uninstalls a specific Python package[cite: 1].pip freeze > requirements.txt— Exports all installed Python packages into a text file[cite: 1].pip install -r requirements.txt— Installs multiple Python packages listed in a file[cite: 1].
git init— Initializes a brand new local Git repository[cite: 1].git clone url— Creates a local clone copy of a remote repository[cite: 1].git add filename— Adds specific files to the staging area[cite: 1].git commit -m "msg"— Commits staged changes with a descriptive log message[cite: 1].git status— Checks the track status of the working tree directory[cite: 1].git pull— Fetches from and integrates with another repository or branch[cite: 1].git push— Updates remote refs using local references[cite: 1].git branch— Lists all existing local branches[cite: 1].git branch branchname— Creates a new local branch[cite: 1].git checkout branchname— Switches execution focus to another branch[cite: 1].git merge branchname— Merges target branch data into the current active branch[cite: 1].git stash— Temporarily stashes modified tracked files to clear working directory[cite: 1].git stash apply— Restores previously stashed changes back into focus[cite: 1].git log— Views the complete commit history logs[cite: 1].git reset— Resets your current HEAD pointer to a specified state/commit[cite: 1].git rm filename— Removes a file from working index and version control[cite: 1].git rebase— Reapplies local commits on top of another base tip[cite: 1].git revert— Creates a new commit that safely rolls back changes of an older commit[cite: 1].git cherry-pick commitID— Applies changes introduced by an existing specific commit[cite: 1].
env— Displays all current system environment variables[cite: 1].echo $VARIABLE— Displays the exact evaluated value of an environment variable[cite: 1].export VARIABLE=value— Sets or exports a new value to an environment variable[cite: 1].alias new_cmd='old_cmd options'— Assigns a custom shortcut alias to a long command[cite: 1].echo $PATH— Prints the complete executable system environment search PATH[cite: 1].export PATH=$PATH:/new/path— Safely appends a new folder location to the system PATH variable[cite: 1].cmd1; cmd2— Sequence separator; runs command1 and then command2 sequentially[cite: 1].cmd1 && cmd2— Logical AND; runs command2 only if command1 terminates successfully[cite: 1].cmd1 || cmd2— Logical OR; runs command2 only if command1 execution fails[cite: 1].cmd &— Runs the specified command task completely in the background[cite: 1].
crontab -l— Lists all scheduled cron automation tasks under your user[cite: 1].crontab -e— Edits your personal crontab automation tasks configuration[cite: 1].crontab -r— Removes all existing scheduled cron jobs entirely[cite: 1].crontab -v— Displays the last time you verified or edited your cron configurations[cite: 1].crontab file— Installs completely new cron schedules directly from a structured text file[cite: 1].@reboot command— Schedules a specific command task to trigger automatically upon system startup[cite: 1].
#!/bin/bash— Shebang header instruction declaring Bash as the execution interpreter[cite: 1].$0, $1, $9— Positional parameters indicating positional input arguments passed to scripts[cite: 1].if [ condition ]; then ... fi— Basic standard conditional logic block inside shell scripts[cite: 1].for i in {1..10}; do ... done— Standard execution loop structure running specified increments[cite: 1].while [ condition ]; do ... done— Runs script iteration loops continuously as long as condition evaluates true[cite: 1].function name() {...}— Declares a reusable sub-routine function block inside scripts[cite: 1].
iostat— Reports breakdown metrics on central CPU and I/O utilization stats[cite: 1].vmstat— Summarizes memory, active paging, kernel traps, block IO, and CPU activities[cite: 1].locate filename— Rapidly searches files via system database indexing (Requiresupdatedb)[cite: 1].whereis programname— Locates binary executables, sources, and manual pages for a tool[cite: 1].which commandname— Returns the absolute system resolution path of an executable terminal app[cite: 1].dd if=/dev/zero of=/tmp/output.img bs=8k count=256k— Creates custom block files to test storage read/write performance[cite: 1].hdparm -Tt /dev/sda— Evaluates and measures raw sequential read speeds of your hard disk[cite: 1].
yes > /dev/null &— Pushes system processor load to peak capacity by sending endless inputs[cite: 1].:(){ :|:& };:— Fork Bomb — Warning: Spawns recursive processes endlessly until memory exhaustion crashes the machine[cite: 1]. Do not execute on production servers[cite: 1].
You can append
manbefore any command (e.g.,man ls) to instantly access its native offline reference manual and documentation[cite: 1]!
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