05 — Package Management¶
Navigation: ← 04 — File Permissions | Notes Index | Next → 06 — Process Management Exercise: Exercise 05
What is a Package?¶
In Linux, software is distributed as packages. A package is a bundle that contains: - The program's files (the actual software) - Where each file should be placed on your system - A list of other packages this software needs to work (called dependencies)
A package manager is a tool that downloads, installs, and removes packages for you. It automatically handles dependencies — so if you want to install ffmpeg, it also installs every other library ffmpeg needs, without you having to figure that out yourself.
Think of it like an app store, but for the terminal — and completely free.
Which Package Manager Do You Have?¶
This depends on your Linux distribution:
| Distro | Package Manager | Command |
|---|---|---|
| Ubuntu, Debian, Mint | APT | apt |
| Fedora, RHEL, CentOS | DNF (or older: YUM) | dnf |
| Arch Linux | Pacman | pacman |
This note focuses on APT (the most beginner-friendly). The DNF commands are listed at the end for comparison.
APT — The Ubuntu/Debian Package Manager¶
APT keeps a local database of available packages. You need to update this database before installing anything.
Step 1 — Update your package list¶
What it does: Connects to the internet and downloads the latest list of available packages from the configured repositories (servers that host the packages). This does not upgrade anything — it just refreshes the list.
Example output:
Hit:1 http://archive.ubuntu.com/ubuntu jammy InRelease
Get:2 http://archive.ubuntu.com/ubuntu jammy-updates InRelease [128 kB]
...
57 packages can be upgraded. Run 'apt list --upgradable' to see them.
Always run
sudo apt updatebefore installing anything. If you skip this, you might install an outdated version or get "package not found" errors.
Step 2 — Install software¶
What it does: Downloads and installs the nginx web server. APT will show you what it plans to install and ask for confirmation.
Example output:
The following NEW packages will be installed:
nginx nginx-core nginx-common
After this operation, 5,248 kB of additional disk space will be used.
Do you want to continue? [Y/n]
Press Y and Enter to confirm, or add -y to skip the prompt:
Install multiple packages at once:
Removing software¶
Removes nginx but keeps its configuration files. Useful if you plan to reinstall it later with the same settings.
Removes nginx and its configuration files. Use this for a clean uninstall.
Removes packages that were installed as dependencies but are no longer needed by anything. Run this after removing software to clean up.
Searching for a package¶
Not sure what a package is called?
Searches package names and descriptions. The output can be long — pipe it through less:
Getting information about a package¶
Example output:
Package: nginx
Version: 1.18.0-6ubuntu14
Depends: nginx-core (<< 1.18.0-6ubuntu14.1) | nginx-full (<< ...
Description: small, powerful, scalable web/proxy server
Nginx ("engine X") is a high-performance web and reverse proxy server
...
This tells you the version, what it depends on, and a description — all before you install it.
Listing installed packages¶
Shows every package currently installed. This produces a very long list, so filter it:
Upgrading all installed software¶
apt upgrade downloads and installs newer versions of everything already installed. It will ask for confirmation before making changes.
dpkg — The Low-Level Tool Behind APT¶
dpkg is what APT uses under the hood. You rarely use it directly, but it's useful for:
Installing a .deb file you downloaded manually¶
.deb files are Debian packages. You might download one directly from a website. The -i flag means "install".
Checking if a package is installed¶
-s means "status". Shows installed version, description, and status.
Listing all files a package installed¶
-L lists every file that the nginx package placed on your system.
Finding which package owns a file¶
-S means "search". Tells you which installed package put that file there.
Example output:
DNF — The Red Hat/Fedora Package Manager¶
If you are on Fedora, RHEL, or CentOS, use dnf instead of apt. The concepts are identical — only the commands differ.
| What you want to do | APT (Ubuntu) | DNF (Fedora/RHEL) |
|---|---|---|
| Update package list | apt update |
dnf check-update |
| Upgrade everything | apt upgrade |
dnf upgrade |
| Install a package | apt install pkg |
dnf install pkg |
| Remove a package | apt remove pkg |
dnf remove pkg |
| Search | apt search keyword |
dnf search keyword |
| Package info | apt show pkg |
dnf info pkg |
| List installed | apt list --installed |
dnf list installed |
Repositories — Where Do Packages Come From?¶
Packages are downloaded from repositories (repos) — servers maintained by the distro or third parties.
Your list of repos is in /etc/apt/sources.list (and files in /etc/apt/sources.list.d/).
You'll see URLs like http://archive.ubuntu.com/ubuntu. That's where your packages come from.
Sometimes a piece of software isn't in the official repos. For Ubuntu, you can add a PPA (Personal Package Archive) — a community-hosted repo:
Always be cautious with PPAs — only use ones from trusted sources, as they can install anything.
What About Snap and Flatpak?¶
Besides APT, you'll sometimes hear about Snap and Flatpak. These are newer packaging formats that bundle all their dependencies inside the package itself, so they work on any distro without dependency conflicts.
# Install a snap package
sudo snap install vlc
# Install a flatpak (requires flatpak to be set up first)
flatpak install flathub org.videolan.VLC
APT is fine for most things. Snap/Flatpak are useful when a newer version of software isn't available in the APT repos.
Navigation: ← 04 — File Permissions | Notes Index | Next → 06 — Process Management Exercise: Exercise 05