Linux Commands and Directories Guide

Important Directories

  • Default Web Server Root Directory
    Location: /var/www/html
    This is the standard location for serving web content on Apache.

  • Downloads Folder
    Location: /home/username/Downloads
    This is where files downloaded from the internet are usually saved by default.

  • Documents Folder
    Location: /home/username/Documents
    A common directory for storing personal documents and files.

  • Desktop Folder
    Location: /home/username/Desktop
    This is the location for files and shortcuts displayed on your desktop screen.

Common Commands

cd

Change the current directory to another one.
Usage: cd [directory]
Example: cd /var/www/html changes to the web server root directory.

ls

List files and directories in the current location or specified path.
Usage: ls [options] [path]
Example: ls -l lists files in a detailed format.

pwd

Print the path of the current working directory.
Usage: pwd
This command shows where you are in the filesystem.

sudo su

Switch to the superuser (root) account, allowing you to perform administrative tasks.
Usage: sudo su
After entering your password, you’ll have root access.

sudo

Execute a command with elevated privileges.
Usage: sudo [command]
Example: sudo apt update runs the update command as an administrator.

mkdir

Create a new directory.
Usage: mkdir [directory name]
Example: mkdir new_folder creates a directory named “new_folder”.

dir

List files and directories, similar to ls.
Usage: dir [options] [path]
This command can be used interchangeably with ls.

mv

Move or rename files and directories.
Usage: mv [source] [destination]
Example: mv /home/username/Downloads/file.txt /home/username/Documents/ moves the file to a different directory.

cp

Copy files or directories.
Usage: cp [source] [destination]
Example: cp /home/username/Downloads/file.txt /home/username/Documents/ copies the file.

rm

Remove files or directories.
Usage: rm [options] [file/directory]
Example: To remove a directory and its contents, use rm -r [directory].

touch

Create an empty file or update the timestamp of an existing file.
Usage: touch [filename]
Example: touch newfile.txt creates an empty file named “newfile.txt”.

cat

Display the contents of a file in the terminal.
Usage: cat [filename]
Example: cat file.txt shows the content of “file.txt”.

gedit

Open the Gedit text editor to edit files.
Usage: gedit [filename]
Example: gedit notes.txt opens “notes.txt” for editing.

kill

Terminate a process using its process ID (PID).
Usage: kill [PID]
Example: kill 1234 stops the process with the ID 1234.

top

Display real-time information about system processes and resource usage.
Usage: top
This command helps monitor system performance.

pkill

Terminate processes by name.

Usage: pkill [process name]
Example:

  • pkill firefox — stops all Firefox processes.
  • pkill node — stops all Node.js processes.

nohup

Run a command immune to hangups (HUP) and continue running even after the terminal is closed. Usage: nohup [command] & Example: nohup python script.py & runs the Python script in the background.

apt-get update

Update the package lists for upgrades and new package installations.
Usage: apt-get update
This command fetches the latest package information.

grep

Search for a specific pattern in files. Usage: grep [pattern] [file]
Example: grep "error" logfile.txt searches for the word “error” in “logfile.txt”.

|

Pipe the output of one command to another.i.e send the output of one command as input to another. Usage: command1 | command2 Example: ls -l | grep "txt" lists all files and filters for those containing “txt”.

>

Redirect the output of a command to a file, overwriting the file if it exists. Usage: command > [filename]
Example: ls > filelist.txt saves the output of ls to “filelist.txt”. *Example: cat file.txt > grep "error" > error.txt saves the output of grep to “error.txt”.

find

Search for files and directories in a specified location. Usage: find [path] -name [filename] Example: find /home/username -name "*.txt" searches for all .txt files in the user’s home directory.

apt install path_of_.deb_file

Install a .deb file package.
Usage: apt install ./filename.deb
Example: apt install ./main.deb installs the specified Debian package.

CURL

To check website status or download files from the internet. Usage: curl [URL] Example: curl https://example.com fetches the content of the specified URL.

apt-get upgrade

Upgrade all installed packages to their latest versions.
Usage: apt-get upgrade
This command updates your installed software.

apt-get install package

Install a specific software package.
Usage: apt-get install [package]
Example: apt-get install vim installs the Vim text editor.

man

Display the manual page for a command, providing detailed information.
Usage: man [command]
Example: man ls shows the manual for the ls command.

whoami

Show the currently logged-in user’s username.
Usage: whoami
This command is useful for confirming your user identity.

zip

Compress a directory and its contents into a zip file.
Usage: zip -r [filename.zip] [foldername]
Example: zip -r archive.zip myfolder creates a zip file of “myfolder”.

unzip

Extract files from a zip archive.
Usage: unzip [filename]
Example: unzip archive.zip extracts files from “archive.zip”.

chmod

Change file or directory permissions.
Usage: chmod [permissions] [file/folder]
Example: chmod +rwx file.txt grants read, write, and execute permissions.
To remove permissions, use chmod -r file.txt.

Important Notes

  1. Folder Names with Spaces:
    If a folder name contains spaces, enclose it in double quotes.

    • mkdir "New Folder" creates a single folder named “New Folder”.
    • mkdir New Folder creates two separate folders named “New” and “Folder”.

  2. Using Wildcards for Operations:
    To perform operations on:

    • All files/folders: use *.
    • Files with a specific extension (e.g., .exe): use *.exe.
    • Files/folders starting with “hello”: use hello*.

  3. Use Relative Paths:
    Prefer using relative paths whenever possible to simplify navigation.

    • Example: mv /home/username/Downloads/index.html /var/www/html/index.html moves a file to the web server directory.