yum/dnf (RHEL/CentOS) basics in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the primary purpose of yum and dnf on RHEL/CentOS systems?

They are package managers used to install, update, and remove software packages on RHEL and CentOS Linux systems.

beginner

How do you update all installed packages using dnf?

Run the command dnf upgrade to upgrade all installed packages to their latest versions.

beginner

What command lists all installed packages using yum?

Use yum list installed to see all packages currently installed on the system.

beginner

How can you search for a package named 'httpd' using dnf?

Use dnf search httpd to find packages related to 'httpd'.

intermediate

What is the difference between yum and dnf?

dnf is the newer package manager that replaces yum with better performance, dependency resolution, and a modern codebase, but they share similar commands.

Which command installs the package 'nano' using dnf?

A dnf update nano

B dnf search nano

C dnf remove nano

D dnf install nano

To install a package, use 'dnf install '.

What does the command 'yum clean all' do?

A Removes all installed packages

B Updates all packages

C Clears cached package data to free disk space

D Searches for packages

'yum clean all' clears cached data like metadata and packages to free space.

Which command lists all available packages using yum?

A yum list available

B yum list installed

C yum search all

D yum info all

'yum list available' shows packages you can install.

If you want to remove a package called 'httpd' using dnf, which command do you use?

A dnf uninstall httpd

B dnf remove httpd

C dnf delete httpd

D dnf erase httpd

'dnf remove ' is the correct command to uninstall a package.

Which package manager is the default on newer RHEL 8+ systems?

A dnf

B apt

C zypper

D yum

dnf replaced yum as the default package manager starting with RHEL 8.

Explain how to install, update, and remove packages using yum or dnf on RHEL/CentOS.

Think about the basic commands for package management.

Describe the main differences and similarities between yum and dnf.

Focus on performance, codebase, and command compatibility.

Practice

1. What is the primary purpose of the yum or dnf command on RHEL/CentOS systems?

easy

A. To configure network settings

B. To monitor system hardware performance

C. To edit text files in the terminal

D. To manage software packages by installing, updating, or removing them

Solution

1. Step 1: Understand the role of yum/dnf

   yum and dnf are package managers used to handle software packages on RHEL/CentOS.

2. Step 2: Identify the correct function

   They allow users to install, update, and remove software easily.

3. Final Answer:

   To manage software packages by installing, updating, or removing them -> Option D

4. Quick Check:

   yum/dnf = software package management [OK]

Hint: yum/dnf commands control software packages [OK]

Common Mistakes:

• Confusing yum/dnf with system monitoring tools
• Thinking yum/dnf edits files or network settings
• Mixing yum/dnf with text editors

2. Which of the following is the correct syntax to install a package named httpd using dnf with automatic yes to prompts?

easy

A. dnf install httpd y

B. dnf -y install httpd

C. dnf -y httpd install

D. dnf httpd install -y

Solution

1. Step 1: Understand dnf command syntax

   The -y option should come immediately after dnf to apply to the entire command.

2. Step 2: Check the order of arguments

   Correct syntax is dnf -y install httpd to install with automatic yes.

3. Final Answer:

   dnf -y install httpd -> Option B

4. Quick Check:

   dnf -y install package = correct syntax [OK]

Hint: Place -y right after dnf for automatic yes [OK]

Common Mistakes:

• Putting -y after the package name
• Mixing argument order causing syntax errors
• Using incorrect command order

3. What will be the output of the command dnf list installed | grep bash on a system where bash is installed?

medium

A. A list of all packages except bash

B. An error saying 'bash not found'

C. A list line showing the bash package details

D. No output at all

Solution

1. Step 1: Understand the command components

   dnf list installed lists all installed packages; piping to grep bash filters lines containing 'bash'.

2. Step 2: Predict output if bash is installed

   Since bash is installed, the output will show the bash package line.

3. Final Answer:

   A list line showing the bash package details -> Option C

4. Quick Check:

   dnf list installed | grep bash = bash package line [OK]

Hint: grep filters output lines containing the keyword [OK]

Common Mistakes:

• Expecting an error if package exists
• Thinking grep excludes matching lines
• Assuming no output means package installed

4. You run sudo yum install -y nginx but get an error: Could not find a valid baseurl for repo. What is the most likely cause?

medium

A. Network connection or repository configuration issue

B. The nginx package does not exist

C. You forgot to use sudo

D. The command syntax is incorrect

Solution

1. Step 1: Analyze the error message

   The error 'Could not find a valid baseurl for repo' means yum/dnf cannot reach the repository URL.

2. Step 2: Identify common causes

   This usually happens due to network issues or wrong repo configuration, not package absence or syntax errors.

3. Final Answer:

   Network connection or repository configuration issue -> Option A

4. Quick Check:

   Repo baseurl error = network or repo config problem [OK]

Hint: Check network and repo config if baseurl error appears [OK]

Common Mistakes:

• Assuming package missing causes baseurl error
• Ignoring need for network access
• Blaming command syntax for repo errors

5. You want to automate updating all packages on a CentOS system without prompts. Which command should you use?

hard

A. sudo dnf update -y

B. sudo yum update

C. sudo dnf install -y

D. sudo yum remove -y

Solution

1. Step 1: Identify the command to update all packages

   dnf update or yum update updates all installed packages.

2. Step 2: Add automation to avoid prompts

   Adding -y automatically answers yes to prompts, enabling automation.

3. Final Answer:

   sudo dnf update -y -> Option A

4. Quick Check:

   dnf update -y = automated full update [OK]

Hint: Use -y with update to automate package upgrades [OK]

Common Mistakes:

• Using install instead of update to upgrade packages
• Forgetting sudo for permission
• Using remove instead of update