apt (Debian/Ubuntu) basics in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the apt update command do?

It refreshes the list of available packages and their versions from the software sources. It does not install or upgrade any packages.

beginner

How do you install a package named curl using apt?

Use the command sudo apt install curl. This downloads and installs the package and its dependencies.

beginner

What is the purpose of apt upgrade?

It upgrades all installed packages to their latest available versions without removing any packages.

intermediate

How can you remove a package but keep its configuration files?

Use sudo apt remove package_name. This removes the package but leaves configuration files intact.

intermediate

What command cleans up downloaded package files that are no longer needed?

The command sudo apt clean deletes the local repository of retrieved package files to free up disk space.

Which command updates the package list but does not install or upgrade packages?

A apt remove

B apt upgrade

C apt install

D apt update

apt update refreshes the package list only. It does not change installed packages.

What does sudo apt install git do?

A Installs git package

B Updates package list

C Upgrades all packages

D Removes git package

This command installs the git package and its dependencies.

Which command upgrades all installed packages to their latest versions?

A apt clean

B apt update

C apt upgrade

D apt autoremove

apt upgrade upgrades installed packages without removing any.

How do you remove a package and its configuration files?

A apt purge

B apt remove

C apt clean

D apt update

apt purge removes the package and its config files.

What command frees disk space by deleting downloaded package files?

A apt install

B apt clean

C apt update

D apt upgrade

apt clean deletes cached package files to free space.

Explain the difference between apt update and apt upgrade.

Think about what changes on your system after each command.

Describe the steps to install a new package and then remove it while keeping its configuration files.

Focus on install and remove commands.

Practice

1. What does the apt update command do on a Debian/Ubuntu system?

easy

A. It upgrades all installed packages to the latest version.

B. It installs new software packages.

C. It removes installed software packages.

D. It refreshes the list of available packages and their versions.

Solution

1. Step 1: Understand the purpose of apt update

   This command downloads the latest package lists from the repositories configured on the system.

2. Step 2: Differentiate from other apt commands

   Unlike install or upgrade, it does not change installed software but only refreshes package info.

3. Final Answer:

   It refreshes the list of available packages and their versions. -> Option D

4. Quick Check:

   apt update refreshes package info [OK]

Hint: Remember: update refreshes info, install adds software [OK]

Common Mistakes:

• Confusing update with install or upgrade
• Thinking update removes packages
• Running update without sudo and expecting changes

2. Which of the following is the correct syntax to install the package named curl using apt?

easy

A. apt install curl

B. apt get install curl

C. apt install -y curl

D. apt-install curl

Solution

1. Step 1: Identify the correct apt install syntax

   The basic command is apt install package_name. Adding -y automatically confirms prompts.

2. Step 2: Evaluate each option

   apt install curl is correct syntax but misses automatic confirmation. apt get install curl is incorrect syntax; it should be apt-get not apt get. apt-install curl uses invalid syntax. apt install -y curl is correct and includes -y for automation.

3. Final Answer:

   apt install -y curl -> Option C

4. Quick Check:

   Use apt install -y for automatic yes [OK]

Hint: Use -y to skip prompts during install [OK]

Common Mistakes:

• Typing 'apt get' instead of 'apt-get'
• Using hyphens incorrectly in command names
• Forgetting sudo before apt commands

3. What will be the output of the command apt search nano if the package nano is available?

medium

A. Lists packages with 'nano' in their name or description.

B. Installs the nano package immediately.

C. Removes the nano package from the system.

D. Updates the nano package to the latest version.

Solution

1. Step 1: Understand the purpose of apt search

   This command searches the package database for names or descriptions matching the search term.

2. Step 2: Analyze the command effect

   It does not install, remove, or update packages; it only lists matching packages.

3. Final Answer:

   Lists packages with 'nano' in their name or description. -> Option A

4. Quick Check:

   apt search lists matching packages [OK]

Hint: Search shows matching packages, doesn't install or remove [OK]

Common Mistakes:

• Thinking search installs packages
• Confusing search with update or upgrade
• Expecting no output if package is not installed

4. You run apt install git but get a permission denied error. What is the most likely fix?

medium

A. Run the command with sudo as sudo apt install git.

B. Use apt update before installing git.

C. Remove git first using apt remove git.

D. Restart the computer and try again.

Solution

1. Step 1: Identify cause of permission denied

   Installing packages requires administrative rights, so running without sudo causes permission errors.

2. Step 2: Apply correct command with elevated rights

   Prepend sudo to gain necessary permissions: sudo apt install git.

3. Final Answer:

   Run the command with sudo as sudo apt install git. -> Option A

4. Quick Check:

   Use sudo for system changes [OK]

Hint: Use sudo for install/remove commands [OK]

Common Mistakes:

• Trying to install without sudo
• Running update instead of fixing permissions
• Restarting without fixing command permissions

5. You want to write a script that installs vim only if it is not already installed. Which command sequence correctly checks and installs using apt?

hard

A. apt search vim && sudo apt install vim

B. if ! dpkg -l | grep -q '^ii vim '; then sudo apt install -y vim; fi

C. sudo apt install vim && echo 'vim installed'

D. dpkg -s vim || apt install vim

Solution

1. Step 1: Understand how to check if vim is installed

   Using dpkg -l lists installed packages; filtering with grep '^ii vim ' checks if vim is installed.

2. Step 2: Use conditional to install only if not installed

   The if ! ...; then ...; fi structure runs install only if vim is missing.

3. Step 3: Evaluate other options

   sudo apt install vim && echo 'vim installed' installs unconditionally. apt search vim && sudo apt install vim searches but does not check installation. dpkg -s vim || apt install vim misses sudo and may fail silently.

4. Final Answer:

   if ! dpkg -l | grep -q '^ii vim '; then sudo apt install -y vim; fi -> Option B

5. Quick Check:

   Check with dpkg, install if missing [OK]

Hint: Use dpkg -l and grep to check before install [OK]

Common Mistakes:

• Installing without checking if package exists
• Forgetting sudo in install command
• Using apt search instead of dpkg for installed check