Basic Linux

Access the Linux Basics Handbook here.

Table of Contents

1. Users in Linux
2. Text Editors
   • Vim
3. Basic File System
4. Paths in Linux
5. Terminal Shortcuts
6. Basic Linux Commands
   • Introducing Commands
   • Working With Directories
   • Working With Files
7. Chmod Calculator
8. Executing Software
9. Process Manipulation
10. Changing Hostname
11. Changing Domain Name
12. Configuring Apache Server
13. Changing Apache Port
14. Software Installation Without Apt
    • From Debian Files
    • From GitHub
15. Error Resolving in Linux Apt
    • Check for Root Access
    • Check Your Connection
    • Editing the Sources List
    • Using Fix-Broken
    • Removing the Apt List
16. Running Multiple Commands in a Single Terminal
    • Semicolon (;)
    • And (&&)
    • Or (||)

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Users in Linux

• Regular User: Home directory
• Root User: Full access [ADMIN] (the superuser of the system)
• Service User: Service access (for servers)

Note:
If a regular user gains root access, they can use sudo before any command to utilize root privileges.
To get full root access, use the sudo su command.

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Text Editors

Vim

Vim is a popular text editor in Linux. Common commands include:

• I: Enter insert mode
• esc: Exit insert mode
• :wq: Exit and save changes
• :q!: Exit without saving changes

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Basic File System

• /bin: Basic programs (e.g., ls, cd, mv)
• /sbin: System programs (e.g., fdisk, sysctl, mkfs)
• /etc: Configuration files (default values)
• /temp: Temporary files
• /usr/bin: Applications (e.g., apt, nmap)
• /usr/share: Application support and data files
• /home: Personal directories of users
• /root: Home directory of the superuser [ADMIN]

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Paths in Linux

Below is an example of a directory structure:

Desktop
├── IntelliJ idea.desktop
├── Joshi
├── Kushal
│   ├── Birthday
│   └── Happy
│       └── hero.txt
├── Prasad
│   ├── Hello
│   └── Sir
├── firefox-esr.desktop
└── libreoffice-startcenter.desktop

Note:

• gedit cd /Desktop/Kushal/Happy/hero.txt is an absolute path (accessible from anywhere).
• gedit hero.txt is a relative path (requires you to be in the Happy directory, for example).

Terminal Shortcuts

• Tab: Autocomplete names
• Double Tab: Open selection menu
• Ctrl + C: Abort the current process
• Ctrl + L: Clear the terminal (same as running clear)
• Ctrl + D: Exit the terminal (same as the exit command)
• Ctrl + Alt + D: Minimize all terminals/commands (toggle)
• Ctrl + U: Clear the current line
• Ctrl + Z: Suspend the current process to the background
• Ctrl + A: Move the cursor to the beginning of the line
• Ctrl + E: Move the cursor to the end of the line
• Shift + Ctrl + C: Copy text in the terminal
• Shift + Ctrl + V: Paste text in the terminal

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Basic Linux Commands

Introducing Commands

• help: Shows basic commands and their uses.
• man: Displays the complete manual for a command or program.
• ls: Lists all files and folders in a directory.
  • ls -a shows hidden files and folders.
  • ls -l displays permissions, dates, and user/group information.
  • ls -R lists directories recursively.
• cd: Change directory.
• pwd: Show the present working directory.
• clear: Clear the terminal screen.
• history: Displays the history of commands.
• echo / printf: Print text to the terminal.
• mkdir: Create a new directory.

Note:

• Prepend a filename with a dot (e.g., .Kushal) to make it hidden.
• Use cd .. to move up one directory.
• To create a directory with spaces, use quotes (e.g., mkdir "Kushal Prasad Joshi") or escape the spaces (e.g., mkdir Kushal\ Prasad\ Joshi).

Working With Directories

• dir: Same as ls.
• mkdir: Create a directory.
• cp: Copy a file or folder.
• mv: Move a file or folder.
• rm: Remove (delete) a file or folder.
  • Use rm -r folder to remove directories recursively.

Working With Files

• sudo su root: Grant root privileges.
• cat: Display the contents of a file.
• nano: Command-line text editor.
• gedit: Graphical text editor.
• chmod: Change file or directory permissions.
  • Example: chmod +wxr filename adds permissions, while chmod -wxr filename removes them.

Note:
In newer Linux versions, you can often use sudo su instead of sudo su root.

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Chmod Calculator

• Usage:

  chmod filename ch-number

  Changes file permissions based on the given numeric mode.
• Change Group:
  Use the chgroup command as needed.

Note:
The format for permissions is typically Owner, Group, Public.

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Executing Software

• ./filename: Execute a shell file.
• bash filename: Run a shell script.
• apt-get update: Update the packages list.
• apt-get upgrade: Upgrade all installed software.
• apt-get install software_name: Install specific software.
• apt-get update software_name: Update packages for a particular software.
• apt-get upgrade software_name: Upgrade a particular software.

Note:

• apt-get update refreshes the package store.
• apt-get upgrade updates all packages and tools.
• In newer Linux distributions, the apt command is often used in place of apt-get.

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Process Manipulation

• top: Displays processes consuming the most resources.
• ps: Shows the current processes.
  • ps -a includes background processes.
• kill: Terminate a process manually.
• w: Shows who is logged on and what they are doing.
• whoami: Displays the current user's username.
• touch: Create an empty file.

Note:

• Use kill PID to terminate a process by its process ID (PID).
• Ctrl + C can stop an ongoing process in the terminal.

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Changing Hostname

1. Gain root access:

   sudo su

2. Navigate to the configuration directory:

   cd /etc

3. Edit the hostname file:

   gedit hostname

4. Restart the system:

   reboot

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Changing Domain Name

1. Gain root access:

   sudo su

2. Navigate to the configuration directory:

   cd /etc

3. Edit the hosts file:

   gedit hosts

4. Start the Apache server:

   service apache2 start

5. Access your domain by entering your IP address and port (e.g., Kushal:80) in a browser.

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Configuring Apache Server

1. Start the Apache server:

   service apache2 start

2. Navigate to the web directory:

   cd /var/www/html/

3. Edit the index page:

   sudo gedit index.html

Note:
Use ifconfig to find your IP address (e.g., inet 192.168.78.141).
Apache typically runs on port 80 by default.

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Changing Apache Port

1. Navigate to the configuration directory:

   cd /etc/apache2

2. Edit the ports configuration file:

   gedit ports.conf

   Change the port number (e.g., from 80 to 8080).
3. Restart Apache:

   service apache2 restart

4. Verify by accessing your IP with the new port (e.g., 192.168.78.141:8080).

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Software Installation Without Apt

From Debian Files

1. Navigate to the Downloads folder:

   cd Downloads

2. Install the package:

   dpkg -i filename

From GitHub

1. Clone the repository:

   git clone url

2. Navigate to the folder:

   cd folder

3. Execute the file:

   ./exefile

Note:
Always follow the installation instructions provided on GitHub for best results.

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Error Resolving in Linux Apt

Check for Root Access

• Ensure you have root privileges by using sudo su.

Check Your Connection

• Verify that you are connected to the internet.

Editing the Sources List

1. Navigate to the apt configuration directory:

   cd /etc/apt

2. Edit the sources list:

   gedit sources.list

   Make sure that important lines are not commented out (lines starting with #).
3. Update the package list:

   apt update

Using Fix-Broken

apt-get install --fix-broken

Removing the Apt List

rm -rf /var/lib/apt/list/*
apt-get update

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Running Multiple Commands in a Single Terminal

Semicolon (;)

• The second command will run regardless of the success of the first command.
  Example:

  cd ; ls

And (&&)

• The second command runs only if the first command is successful.
  Example:

  cd && ls

Or (||)

• The second command runs only if the first command fails.
  Example:

  cd || ls

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License

This repository is licensed under the MIT License. You are free to use, modify, and distribute the code, provided that the original copyright notice and license text are included in all copies or substantial portions of the Software.

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