Ubuntu Terminal Basics

Introduction

The terminal is one of the most powerful tools in Ubuntu, providing direct access to the underlying system through a text-based interface. While graphical interfaces make many tasks accessible, mastering the terminal unlocks greater efficiency, automation capabilities, and deeper control over your Ubuntu system.

In this guide, we'll explore the fundamental terminal commands and concepts that every Ubuntu user should know. Whether you're completely new to Linux or looking to strengthen your foundation, these basics will set you on the path to terminal proficiency.

What is the Terminal?

The terminal (also called the command line or shell) is a text-based interface where you type commands to interact with your computer. In Ubuntu, the default terminal application runs a shell program called Bash (Bourne Again SHell), though other shells like Zsh or Fish are also available.

Opening the Terminal

There are several ways to open a terminal in Ubuntu:

• Press Ctrl + Alt + T (keyboard shortcut)
• Search for "Terminal" in the applications menu
• Right-click on the desktop and select "Open Terminal" (if this option is enabled)

Understanding the Terminal Prompt

When you open the terminal, you'll see a prompt that typically looks like this:

username@hostname:~$

This prompt tells you:

• Your username
• The hostname of your computer
• Your current directory (~ represents your home directory)
• The $ symbol indicates you're logged in as a regular user (a # would indicate root user)

Basic Navigation Commands

1. pwd - Print Working Directory

Shows your current location in the file system.

bash

$ pwd
/home/username

2. ls - List Files and Directories

Displays the contents of the current directory.

bash

$ ls
Documents  Downloads  Music  Pictures  Videos

Common options:

• ls -l - Long format showing permissions, size, etc.
• ls -a - Shows all files including hidden ones (starting with .)
• ls -h - Human-readable file sizes

bash

$ ls -la
total 112
drwxr-xr-x 16 username username 4096 Mar 10 14:22 .
drwxr-xr-x  3 root     root     4096 Jan 15 10:45 ..
-rw-------  1 username username 9320 Mar 10 14:20 .bash_history
drwxr-xr-x  2 username username 4096 Mar  8 09:12 Documents
drwxr-xr-x  3 username username 4096 Mar  9 17:45 Downloads

3. cd - Change Directory

Navigates between directories.

bash

$ cd Documents
$ pwd
/home/username/Documents

Special directory references:

• cd ~ - Go to your home directory
• cd .. - Go up one directory level
• cd - - Go to previous directory

File and Directory Operations

1. mkdir - Make Directory

Creates a new directory.

bash

$ mkdir Projects
$ ls
Documents  Downloads  Music  Pictures  Projects  Videos

Create nested directories with the -p option:

bash

$ mkdir -p Projects/WebDev/HTML

2. touch - Create Empty Files

Creates a new empty file or updates the timestamp of an existing file.

bash

$ touch notes.txt
$ ls
Documents  Downloads  Music  notes.txt  Pictures  Projects  Videos

3. cp - Copy Files or Directories

Copies files or directories from one location to another.

bash

$ cp notes.txt Documents/
$ ls Documents/
notes.txt

Copy directories with the -r (recursive) option:

bash

$ cp -r Projects/ Documents/

4. mv - Move or Rename Files

Moves files or directories, also used for renaming.

Move a file:

bash

$ mv notes.txt Documents/

Rename a file:

bash

$ mv notes.txt todo.txt

5. rm - Remove Files or Directories

Deletes files or directories.

bash

$ rm todo.txt

Remove directories with -r (recursive) option:

bash

$ rm -r Projects/

Warning: Be careful with rm, especially when combined with wildcards or the -rf flag, as deleted files cannot be easily recovered!

Viewing and Editing Files

1. cat - Concatenate and Display Files

Displays the contents of a file.

bash

$ cat notes.txt
This is my notes file.
It contains important information.

2. less - View Files with Pagination

Views file contents with scrolling capability.

bash

$ less large_file.txt

Navigation in less:

• Space or f - Forward one page
• b - Back one page
• /pattern - Search for text
• q - Quit

3. head and tail - View Beginning or End of Files

head shows the first 10 lines of a file:

bash

$ head large_file.txt
# Shows first 10 lines

tail shows the last 10 lines:

bash

$ tail large_file.txt
# Shows last 10 lines

You can specify the number of lines:

bash

$ head -n 5 large_file.txt
# Shows first 5 lines

4. Text Editors

Several text editors are available in the terminal:

• nano - Beginner-friendly editor

  bash

  $ nano filename.txt

• vim - More powerful but has a steeper learning curve

  bash

  $ vim filename.txt

Finding Files and Content

1. find - Search for Files

Searches for files in a directory hierarchy.

bash

$ find . -name "*.txt"
./Documents/notes.txt
./report.txt

Find by type:

bash

$ find . -type d -name "Project*"
./Projects
./Documents/ProjectBackup

2. grep - Search Within Files

Searches for patterns in files.

bash

$ grep "important" notes.txt
This file contains important information.

Recursive search in directories:

bash

$ grep -r "Ubuntu" Documents/
Documents/notes.txt:Ubuntu is a Linux distribution.
Documents/tutorial.txt:Ubuntu terminal basics are essential.

Working with Permissions

1. Understanding Permissions

File permissions are displayed with ls -l:

bash

$ ls -l notes.txt
-rw-r--r-- 1 username groupname 45 Mar 10 14:30 notes.txt

The permission string -rw-r--r-- means:

• First character: File type (- for regular file, d for directory)
• Next three characters: Owner permissions (rw- = read, write, no execute)
• Next three characters: Group permissions (r-- = read, no write, no execute)
• Last three characters: Others permissions (r-- = read, no write, no execute)

2. chmod - Change Permissions

Changes file or directory permissions.

bash

$ chmod u+x script.sh
$ ls -l script.sh
-rwxr--r-- 1 username groupname 80 Mar 10 14:35 script.sh

Common patterns:

• chmod u+x - Add execute permission for the owner
• chmod 755 - Set rwx for owner, rx for group and others
• chmod 644 - Set rw for owner, r for group and others

Command Execution and Redirection

1. Command History

Access previously used commands:

• Use ↑ and ↓ arrow keys to navigate history
• history command shows the command history list

bash

$ history
  1  pwd
  2  ls -la
  3  cd Documents

Execute a command from history:

bash

$ !3
cd Documents

2. Input/Output Redirection

Redirect output to a file:

bash

$ ls -la > file_list.txt

Append output to an existing file:

bash

$ echo "New line" >> notes.txt

Redirect input from a file:

bash

$ sort < unsorted.txt

3. Pipes

Connect the output of one command to the input of another:

bash

$ ls -la | grep "Documents"
drwxr-xr-x  2 username username 4096 Mar  8 09:12 Documents

Chain multiple commands:

bash

$ cat large_file.txt | grep "important" | sort > important_lines.txt

Process Management

1. ps - List Running Processes

Shows currently running processes.

bash

$ ps
  PID TTY          TIME CMD
 1234 pts/0    00:00:00 bash
 5678 pts/0    00:00:00 ps

For more detailed information:

bash

$ ps aux

2. kill - Terminate Processes

Terminates a process by PID (Process ID).

bash

$ kill 1234

Force kill a stubborn process:

bash

$ kill -9 1234

3. Background Processes

Run a command in the background by adding &:

bash

$ long_running_command &
[1] 1234

Suspend a running process with Ctrl+Z, then:

• bg - Continue the process in the background
• fg - Bring the process to the foreground

Terminal Shortcuts

Some helpful keyboard shortcuts to improve efficiency:

• Ctrl+C - Cancel the current command
• Ctrl+L - Clear the screen (alternative to clear command)
• Ctrl+A - Move cursor to beginning of line
• Ctrl+E - Move cursor to end of line
• Ctrl+W - Delete the word before the cursor
• Ctrl+U - Delete from cursor to beginning of line
• Tab - Auto-complete commands and filenames

Package Management Basics

Ubuntu uses apt (Advanced Package Tool) for package management.

Update package lists:

bash

$ sudo apt update

Upgrade installed packages:

bash

$ sudo apt upgrade

Install a package:

bash

$ sudo apt install package-name

Remove a package:

bash

$ sudo apt remove package-name

Search for packages:

bash

$ apt search keyword

Getting Help

When you're unsure about a command, there are several ways to get help:

1. man - Manual Pages

Detailed documentation for commands.

bash

$ man ls

Navigate with the same keys as less (Space, b, q, etc.).

2. --help Option

Most commands provide basic help with the --help option.

bash

$ ls --help

3. info - More Detailed Documentation

Some commands have more extensive documentation in the info system.

bash

$ info ls

Practical Examples

Let's look at some real-world tasks you might perform with the terminal:

Example 1: Finding Large Files

bash

$ find /home -type f -size +100M -exec ls -lh {} \; | sort -k5,5hr

This command finds files larger than 100MB in the /home directory and lists them with their sizes in human-readable format, sorted by size.

Example 2: Batch Renaming Files

bash

$ for f in *.jpg; do mv "$f" "vacation_$(date +%Y%m%d)_$f"; done

This renames all .jpg files by adding "vacation_" and the current date as a prefix.

Example 3: Creating a Backup

bash

$ tar -czvf backup_$(date +%Y%m%d).tar.gz Documents/

This creates a compressed backup of the Documents directory with the current date in the filename.

Example 4: System Monitoring

bash

$ watch -n 1 'free -m; echo ""; df -h'

This displays memory and disk usage, updating every second.

Summary

The Ubuntu terminal provides a powerful interface for interacting with your system. In this guide, we've covered:

• Basic navigation with pwd, ls, and cd
• File operations with mkdir, touch, cp, mv, and rm
• Viewing and editing files
• Finding files and content with find and grep
• Working with permissions
• Command execution, redirection, and pipes
• Process management
• Package management with apt
• Getting help with man and --help

While it may seem intimidating at first, regular practice with these commands will build your confidence and efficiency. The terminal is an essential tool for any Ubuntu user, especially those interested in programming or system administration.

Additional Resources

For further practice and learning:

1. Practice these commands regularly
2. Explore online terminal games like "Terminus" or "Over The Wire: Bandit"
3. Create your own shell scripts to automate common tasks
4. Try to use the terminal for daily tasks instead of the GUI when possible

Exercises

1. Create a directory structure for a hypothetical project with subdirectories for source code, documentation, and resources.
2. Write a command to find all .txt files in your home directory that contain the word "important".
3. Create a simple shell script that displays the current date, disk usage, and memory usage.
4. Use redirection to combine the contents of multiple text files into a single file.
5. Find the five largest files in your Documents directory.