🦸From Zero to Hero: Navigating Linux Commands Like a Pro

Here is a list of essential Linux commands for various operations:

File Operations:

• ls: Lists all files and directories in the present working directory.

• ls -R: Lists files in sub-directories as well.

• ls -a: Shows hidden files.

• ls -al: Lists files and directories with detailed information.

• cd directoryname: Changes the directory.

• cd ..: Moves one level up.

• pwd: Displays the present working directory.

• cat > filename: Creates a new file.

• cat filename: Displays the file content.

• cat file1 file2 > file3: Joins two files and stores the output in a new file.

• touch filename: Creates or modifies a file.

• rm filename: Deletes a file.

• cp source destination: Copies files from the source path to the destination path.

• mv source destination: Moves files from the source path to the destination path.

• find / -name filename: Finds a file or a directory by its name starting from root.

• file filename: Determines the file type.

• less filename: Views the file content page by page.

• head filename: Views the first ten lines of a file.

• tail filename: Views the last ten lines of a file.

• lsof: Shows which files are opened by which process.

• du -h --max-depth=1: Shows the size of each directory.

Directory Operations:

• mkdir directoryname: Creates a new directory in the present working directory.

• rmdir directoryname: Deletes a directory.

• cp -r source destination: Copies directories recursively.

• mv olddir newdir: Renames directories.

• find / -type d -name directoryname: Finds a directory starting from root.

Process Operations:

• ps: Displays currently active processes.

• top: Displays all running processes.

• kill pid: Kills the process with the given PID.

• pkill name: Kills the process with the given name.

• bg: Resumes suspended jobs without bringing them to the foreground.

• fg: Brings the most recent job to the foreground.

• fg n: Brings job n to the foreground.

• renice +n [pid]: Changes the priority of a running process.

File Permissions:

• chmod octal filename: Change the permissions of a file.

• chown ownername filename: Change file owner.

• chgrp groupname filename: Change group owner.

Networking:

• ping host: Ping a host and output results.

• whois domain: Get whois information for a domain.

• dig domain: Get DNS information for a domain.

• netstat -pnltu: Display various network related information.

• ifconfig: Displays IP addresses of all network interfaces.

• ssh user@host: Remote login into the host as a user.

• scp: Transfers files between hosts over SSH.

• wget url: Download files from the web.

• curl url: Sends a request to a URL and returns the response.

• traceroute domain: Prints the route that a packet takes to reach the domain.

• mtr domain: Combines the functionality of traceroute and ping.

• ss: Investigates sockets.

• nmap: Network exploration tool and security scanner.

Archives and Compression:

• tar cf file.tar files: Create a tar archive containing files.

• tar xf file.tar: Extract files from a tar archive.

• gzip file: Compresses a file.

• gzip -d file.gz: Decompresses a file.

• zip -r file.zip files: Create a zip archive.

• unzip file.zip: Extract the contents of a zip file.

Text Processing:

• grep pattern files: Search for a pattern in files.

• grep -r pattern dir: Search recursively for a pattern in a directory.

• echo 'text': Prints text.

• sed 's/string1/string2/g' filename: Replaces string1 with string2 in a file.

• diff file1 file2: Compares two files and shows the differences.

• wc filename: Count lines, words, and characters in a file.

• awk: A versatile programming language for working on files.

• sed -i 's/string1/string2/g' filename: Replace string1 with string2 in a file.

• cut -d':' -f1 /etc/passwd: Cut out the first field of each line in /etc/passwd.

Disk Usage:

• df: Shows disk usage.

• du: Shows directory space usage.

• free: Show memory and swap usage.

• whereis app: Show possible locations of an app.

System Info:

• date: Show the current date and time.

• cal: Show this month's calendar.

• uptime: Show current uptime.

• w: Display who is online.

• whoami: Who you are logged in as.

• uname -a: Show kernel information.

• df -h: Disk usage in a human-readable format.

• du -sh: Disk usage of the current directory in a human-readable format.

• free -m: Show free and used memory in MB.

Package Installations:

• sudo apt-get update: Updates package lists for upgrades.

• sudo apt-get upgrade: Upgrades all upgradable packages.

• sudo apt-get install pkgname: Install a package.

• sudo apt-get remove pkgname: Removes a package.

Others (mostly used in scripts):

• command1 ; command2: Run command1 and then command2.

• command1 && command2: Run command2 if command1 is successful.

• command1 || command2: Run command2 if command1 is not successful.

• command &: Run command in the background.

Version Control (Git commands):

• git init: Initialize a local Git repository.

• git clone url: Create a local copy of a remote repository.

• git add filename: Add a file to the staging area.

• git commit -m "Commit message": Commit changes with a message.

• git status: Check the status of the working directory.

• git pull: Pull latest changes from the remote repository.

• git push: Push changes to the remote repository.

• git branch: List all local branches.

• git branch branchname: Create a new branch.

• git checkout branchname: Switch to a branch.

• git merge branchname: Merge a branch into the active branch.

• git stash: Stash changes in a dirty working directory.

• git stash apply: Apply changes from a stash.

• git log: View commit history.

• git reset: Reset your HEAD pointer to a previous commit.

• git rm filename: Remove a file from version control.

• git rebase: Reapply commits on top of another base tip.

• git revert: Create a new commit that undoes all the changes made in a particular commit.

• git cherry-pick commitID: Apply the changes introduced by some existing commits.

Environment Variables:

• env: Display all environment variables.

• `echo $V

ARIABLE`: Display the value of an environment variable.

• export VARIABLE=value: Set the value of an environment variable.

• alias new_command='old_command options': Create a new command that executes the old command with the specified options.

• echo $PATH: Print the PATH environment variable.

• export PATH=$PATH:/new/path: Add /new/path to the PATH.

Job Scheduling (Cron Jobs):

• crontab -l: List all your cron jobs.

• crontab -e: Edit your cron jobs.

• crontab -r: Remove all your cron jobs.

• crontab -v: Display the last time you edited your cron jobs.

• crontab file: Install a cron job from a file.

• @reboot command: Schedule a job to run at startup.

Package Installations (using pip, a Python package installer):

• pip install packagename: Install a Python package.

• pip uninstall packagename: Uninstall a Python package.

• pip freeze > requirements.txt: Freeze the installed packages into a requirements file.

• pip install -r requirements.txt: Install packages from a requirements file.

Shell Scripting:

• #!/bin/bash: Shebang line to specify the script interpreter.

• $0, $1, ..., $9, ${10}, ${11}: Script arguments.

• if [condition]; then ... fi: if statement in Bash scripts.

• for i in {1..10}; do ... done: for loop in Bash scripts.

• while [condition]; do ... done: while loop in Bash scripts.

• function name() {...}: Define a function.

System Monitoring and Performance:

• iostat: Reports CPU statistics and input/output statistics for devices, partitions, and network filesystems.

• vmstat: Reports information about processes, memory, paging, block IO, traps, disks, and CPU activity.

• htop: An interactive process viewer for Unix systems.

Search and Find:

• locate filename: Find a file by its name.

• whereis programname: Locate the binary, source, and manual page files for a command.

• which commandname: Shows the full path of shell commands.

Compression / Archives:

• tar -cvf archive.tar dirname/: Create a tar archive.

• tar -xvf archive.tar: Extract a tar archive.

• tar -jcvf archive.tar.bz2 dirname/: Create a compressed bz2 archive.

• tar -jxvf archive.tar.bz2: Extract a bz2 archive.

Disk Usage:

• dd if=/dev/zero of=/tmp/output.img bs=8k count=256k: Create a file of a certain size for testing disk speed.

• hdparm -Tt /dev/sda: Measure the read speed of your hard drive.

Others:

• yes > /dev/null &: Use this command to push a system to its limit.

• :(){ :|:& };::: A fork bomb – handle with care. Do not run this command on a production system.

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Remember, you can always use the man command (e.g., man ls) to get more information about each command.