M16 — Software packages (apt and dnf)

Prerequisites#

• Root or sudo on a practice VM (do not practice removals on a production laptop without a snapshot).
• M2-level comfort with the terminal.

Learning objectives#

1. Explain package, repository, and dependency in plain language.
2. Search, install, verify, update, and remove software with apt and dnf.
3. Read a short “same job, two commands” table without memorizing only one family.
4. Install a small utility (tree or htop) on a disposable VM and remove it cleanly.

Which manager do I have?#

. /etc/os-release
echo "$PRETTY_NAME"
command -v apt && echo "→ use apt columns"
command -v dnf && echo "→ use dnf columns"

Drafting box: Debian GNU/Linux 13 (trixie) with apt only. All apt outputs below are from that box on 2026-09-26 IST. dnf lines are the standard Fedora/RHEL-family equivalents for you to run where dnf exists.

1. Mental model#

You rarely download random .deb / .rpm files from the web when starting out — use the manager so signatures and dependencies stay consistent.

2. Side-by-side command map#

Notes:

• On older RHEL-family systems you may still see yum; on current releases dnf is the front end (often yum is an alias).
• Oracle Linux, AlmaLinux, Rocky Linux, CentOS Stream → think dnf family.
• Ubuntu, Debian, Linux Mint, Pop!_OS → think apt family.

3. apt walk-through (executed on Debian 13)#

Search#

apt-cache search '^tree$'
# or: apt search '^tree$'

Lab output:

tree - displays an indented directory tree, in color

Policy / candidate version#

apt-cache policy tree

Lab output (abridged):

tree:
  Installed: (none)
  Candidate: 2.2.1-1
  Version table:
     2.2.1-1 500
        500 http://deb.debian.org/debian trixie/main amd64 Packages

Install (needs sudo)#

sudo apt update
sudo apt install -y tree
tree --version | head -1

Lab verify: tree v2.2.1 …

tree -L 2 /tmp/linux-lab-pushpjeet/m15/project

Lab output:

/tmp/linux-lab-pushpjeet/m15/project
├── config.ini
├── docs
│   └── readme.md
└── src
    └── app.py

3 directories, 3 files

Remove#

sudo apt remove -y tree

After removal, tree is gone from the PATH; the package can be installed again later the same way.

4. dnf walk-through (run on a Fedora/RHEL-family VM)#

sudo dnf search tree
sudo dnf info tree
sudo dnf install -y tree
tree --version
sudo dnf remove -y tree

Same learning goals, different verb spelling. If you use both Ubuntu at home and RHEL at work, keep the section 2 table nearby for a week — then it sticks.

5. Good habits#

1. Snapshot or disposable VM before mass upgrades.
2. Prefer apt install / dnf install over pasting untrusted install scripts.
3. Read what will be removed when you remove a package that looks “small” but pulls a desktop stack — the manager shows the plan; say no if surprised.
4. After experiments: autoremove unused dependencies.
5. For servers, pin critical versions only when you know why (advanced; not required here).

Common mistakes#

Hands-on lab (30–45 minutes)#

Use your practice VM (WSL, cloud, or VirtualBox). Pick the column that matches your distro.

Tasks#

1. Identify the manager (apt or dnf).
2. Update metadata.
3. Search for tree and htop.
4. Install one of them (tree recommended).
5. Run it against a directory you know.
6. Remove it again.
7. (Optional) Install rsync and openssh-client if M15 needed them.

Verify#

• Before install: command not found (or old version noted).
• After install: command -v tree prints a path; --version works.
• After remove: command not found again.

Practice: check your understanding#

Multiple choice#

Q1. On Ubuntu, which command installs htop?

• A. sudo dnf install htop
• B. sudo apt install htop
• C. tar -xzf htop
• D. chmod +x htop

Answer: B.

Q2. What does refreshing the package index do?

• A. Deletes unused home directories
• B. Updates the local list of available packages/versions from repositories
• C. Reboots the kernel
• D. Compresses /var/log

Answer: B.

Q3. Fedora / RHEL-family systems typically use:

• A. apt only
• B. dnf (with yum often as compatibility)
• C. brew as the system manager
• D. pip for all OS tools

Answer: B.

Flashcards#

Match the columns — apt ↔ dnf#

Fill in the blank#

1. Debian install: sudo apt _______ tree
   Answer: install

2. RHEL-family install: sudo dnf _______ tree
   Answer: install

3. Refresh apt indexes: sudo apt _______
   Answer: update

4. Remove on Fedora: sudo dnf _______ tree
   Answer: remove

Order the steps — install tree safely#

1. Confirm you are on a practice VM / have a snapshot
2. sudo apt update or sudo dnf check-update
3. Search so the name is correct (tree not a random lookalike)
4. sudo apt install tree or sudo dnf install tree
5. Verify with tree --version and a quick tree -L 1 …
6. (Lab only) Remove when finished

Correct order: 1 → 2 → 3 → 4 → 5 → 6

Mini terminal challenge#

Challenge: Install tree#

Goal: Install, use, remove tree with your distro’s manager.

Setup: Disposable VM with sudo.

Tasks:

1. Update indexes.
2. Install tree.
3. Run tree -L 2 on any project directory.
4. Remove tree.

Verify: Steps 3 works; after step 4, command -v tree is empty.

Stretch: Install htop, run it once (F10 to quit), remove it.

Module wrap#

You can search, install, verify, and remove packages on both Debian/Ubuntu (apt) and Fedora/RHEL-family (dnf) systems. Next: accounts and groups (M17).

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