RED HAT ENTERPRISE LINUX

Flatpak and
Application Repositories

Configure access to Flatpak repositories

CIS126RH | RHEL System Administration 1
Mesa Community College

Flatpak is a modern application packaging format that delivers sandboxed applications independent of the host operating system version. On RHEL, Flatpak complements the RPM package system by providing access to a broader range of desktop applications from the Flathub community repository. This module covers how Flatpak works, how to configure remote repositories, and how to install and manage Flatpak applications.

Learning Objectives

1. Explain what Flatpak is and how it differs from RPM — Describe the sandboxed application model and why Flatpak exists alongside RPM
2. Install the Flatpak tooling on RHEL — Install the flatpak package and confirm the runtime is ready
3. Add and manage Flatpak remotes — Configure access to Flathub and other repositories using flatpak remote-add
4. Install, update, and remove Flatpak applications — Use flatpak install, flatpak update, and flatpak uninstall to manage the application lifecycle

What is Flatpak?

Flatpak is an application packaging and distribution framework that bundles applications with their dependencies into a sandboxed container that runs independently of the host OS version.

• Applications run in an isolated sandbox — limited access to the host system
• Each application bundles its own runtime libraries — no host dependency conflicts
• The same Flatpak package runs on RHEL 8, RHEL 9, Fedora, Ubuntu, and others
• Applications are updated independently of the OS package update cycle
• Primarily used for desktop GUI applications — not server daemons

Flatpak vs RPM

Installing Flatpak on RHEL

The flatpak package is available in the AppStream repository and must be installed before any Flatpak operations can be performed.

# Install the flatpak package from AppStream
$ sudo dnf install -y flatpak

# Verify the installation
$ flatpak --version
Flatpak 1.14.4

# List currently configured remotes — none yet
$ flatpak remote-list
(no output)

# The flatpak command structure
# flatpak COMMAND [OPTIONS] [ARGUMENTS]
# Common commands: remote-add, remote-list, remote-delete
#                  install, update, uninstall, list, info, run

Flatpak Remotes

A remote is Flatpak's term for a repository — a server that hosts Flatpak applications and runtimes. Remotes are added with flatpak remote-add and can be system-wide or per-user.

Adding the Flathub Remote

Flathub is the primary community repository for Flatpak applications. It hosts thousands of desktop applications from Firefox to LibreOffice to development tools.

# Add Flathub as a system-wide remote
# --if-not-exists prevents errors if already added
$ sudo flatpak remote-add --if-not-exists --system \
    flathub \
    https://dl.flathub.org/repo/flathub.flatpakrepo

# Add Flathub as a user remote (no sudo needed)
$ flatpak remote-add --if-not-exists --user \
    flathub \
    https://dl.flathub.org/repo/flathub.flatpakrepo

# Confirm the remote was added
$ flatpak remote-list
Name     Options
flathub  system,oci

# Show detailed information about the remote
$ flatpak remote-list --show-details
flathub  Flathub  https://dl.flathub.org/repo/  system,oci

The .flatpakrepo File

A .flatpakrepo file is a text descriptor that defines a Flatpak remote. It can be passed to flatpak remote-add as a URL or a local file path.

# Contents of flathub.flatpakrepo — an INI-style descriptor
[Flatpak Repo]
Title=Flathub
Url=https://dl.flathub.org/repo/
Homepage=https://flathub.org
Comment=Central repository of Flatpak applications
Description=Central repository of Flatpak applications
Icon=https://dl.flathub.org/repo/logo.svg
GPGKey=mQINBFlD2sABEADsiUZUO...

# Download and inspect a .flatpakrepo file before adding it
$ curl -O https://dl.flathub.org/repo/flathub.flatpakrepo
$ cat flathub.flatpakrepo

# Add from a local file instead of a URL
$ sudo flatpak remote-add --if-not-exists \
    flathub flathub.flatpakrepo

Managing Remotes

# List all configured remotes
$ flatpak remote-list
Name     Options
flathub  system,oci

# List remotes for all scopes
$ flatpak remote-list --all

# Show the applications available in a remote
$ flatpak remote-ls flathub

# Search available applications across configured remotes
$ flatpak search firefox
Application ID              Version  Branch  Remotes  Description
org.mozilla.firefox         125.0    stable  flathub  Firefox Web Browser

# Disable a remote without removing it
$ sudo flatpak remote-modify --disable flathub

# Re-enable a disabled remote
$ sudo flatpak remote-modify --enable flathub

# Remove a remote
$ sudo flatpak remote-delete flathub

Installing Flatpak Applications

Flatpak applications are identified by a reverse-domain application ID such as org.mozilla.firefox. Each application also has a branch — typically stable.

# Install an application by ID — prompts for confirmation
$ sudo flatpak install flathub org.mozilla.firefox
Installing: org.mozilla.firefox/x86_64/stable from flathub
Downloading runtime org.freedesktop.Platform...
Installing application org.mozilla.firefox...
Is this ok [y/N]: y

# Install without confirmation
$ sudo flatpak install -y flathub org.mozilla.firefox

# Install as the current user (no sudo)
$ flatpak install --user flathub org.mozilla.firefox

# Install from a .flatpakref file (single application descriptor)
$ flatpak install --from firefox.flatpakref

Listing and Running Applications

# List all installed Flatpak applications
$ flatpak list
Name            Application ID              Version  Branch  Origin   Installation
Firefox         org.mozilla.firefox         125.0    stable  flathub  system

# List only applications (exclude runtimes)
$ flatpak list --app

# Show detailed information about an installed application
$ flatpak info org.mozilla.firefox
ID:             org.mozilla.firefox
Ref:            app/org.mozilla.firefox/x86_64/stable
Origin:         flathub
Installation:   system
Installed size: 248.4 MB

# Run an installed Flatpak application
$ flatpak run org.mozilla.firefox

# List all installed runtimes
$ flatpak list --runtime

Updating and Removing Applications

Updating

# Update all installed Flatpak applications and runtimes
$ sudo flatpak update

# Update a specific application
$ sudo flatpak update org.mozilla.firefox

# Check what updates are available without installing
$ flatpak remote-ls --updates flathub

Removing

# Remove a specific application
$ sudo flatpak uninstall org.mozilla.firefox

# Remove and clean up unused runtimes in one step
$ sudo flatpak uninstall --unused

# Remove all Flatpak data for a user (home directory data)
$ sudo flatpak uninstall --delete-data org.mozilla.firefox

Application Data and Permissions

Flatpak applications run in a sandbox with limited access to the host system. Understanding where data is stored and how permissions work helps with troubleshooting and administration.

Where Flatpak stores data

Viewing and overriding sandbox permissions

# Show the sandbox permissions for an application
$ flatpak info --show-permissions org.mozilla.firefox

# Grant an application access to the home directory
$ sudo flatpak override --filesystem=home org.mozilla.firefox

# Reset all permission overrides for an application
$ sudo flatpak override --reset org.mozilla.firefox

Flatpak Command Quick Reference

Flatpak in a Restricted Environment

The RHCSA exam environment may have limited or no internet access. These techniques handle Flatpak configuration when direct access to Flathub is not available.

Using a local or institutional mirror

# Add a remote pointing to an internal mirror
$ sudo flatpak remote-add --if-not-exists \
    local-flathub \
    http://mirror.example.com/flatpak/flathub.flatpakrepo

Installing from a .flatpakref file

# A .flatpakref file specifies one application and its source remote
$ cat firefox.flatpakref
[Flatpak Ref]
Name=org.mozilla.firefox
Branch=stable
Url=https://dl.flathub.org/repo/
GPGKey=mQINBFlD2sA...

# Install from the file — adds the remote if not already present
$ flatpak install --from firefox.flatpakref

Common Mistakes

Knowledge Check

Answer these before moving to the next slide.

1. What is the difference between a Flatpak remote and an RPM repository? What command adds a Flatpak remote?
2. Write the command to add the Flathub remote as a system-wide remote, using the URL https://dl.flathub.org/repo/flathub.flatpakrepo, without producing an error if it already exists.
3. After adding the Flathub remote, write the command to confirm it is listed as an active system remote.
4. Write the command to search for applications related to the keyword image editor across all configured remotes.
5. What is the difference between --system and --user scope when adding a Flatpak remote?
6. After removing a Flatpak application, disk space has not been reclaimed. What command cleans up unused runtimes?

Knowledge Check — Answers

1. A Flatpak remote is functionally equivalent to an RPM repository — it is a server that hosts applications and their metadata. The key difference is terminology: Flatpak calls them "remotes" and they are added with flatpak remote-add, while RPM repositories are configured in .repo files.
2. sudo flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
   The --system flag is optional — system is the default scope when using sudo.
3. flatpak remote-list — the output should show flathub with system in the options column.
4. flatpak search "image editor" — quotes group the two-word search term so both words are treated as one query.
5. System scope (--system) stores the remote in /var/lib/flatpak/ and makes it available to all users — requires sudo. User scope (--user) stores it in ~/.local/share/flatpak/ and affects only the current user — no sudo needed.
6. sudo flatpak uninstall --unused — removes all installed runtimes that are not required by any currently installed application.

Key Takeaways

1. Flatpak complements RPM — it does not replace it. RPM handles system software, services, and CLI tools. Flatpak handles desktop GUI applications with sandboxing and cross-distribution compatibility. Flatpak calls its repositories remotes.
2. Add remotes with flatpak remote-add. Use sudo flatpak remote-add --if-not-exists remote-name URL for system-wide access. Verify with flatpak remote-list. The Flathub URL is https://dl.flathub.org/repo/flathub.flatpakrepo.
3. Install using the full application ID. sudo flatpak install flathub org.mozilla.firefox — always use the reverse-domain ID, not a display name. Verify with flatpak list --app and flatpak info org.app.Name.
4. System scope requires sudo; user scope does not. System remotes are in /var/lib/flatpak/ and available to all users. User remotes are in ~/.local/share/flatpak/ and affect only the current user. The RHCSA exam tests system-wide configuration.

Graded Lab

• Install the flatpak package using dnf and confirm the version with flatpak --version
• Add the Flathub remote as a system-wide remote using the official .flatpakrepo URL. Use --if-not-exists to make the command safe to re-run.
• Verify the remote is configured with flatpak remote-list --show-details and confirm the URL and system scope appear in the output
• Search for an application of your choice using flatpak search. Note the full application ID from the output.
• Install the application using its full ID from the Flathub remote. Confirm installation with flatpak list --app.
• Run flatpak info on the installed application to view its installed size, origin remote, and installation scope.
• Remove the application with flatpak uninstall and then run flatpak uninstall --unused to clean up any orphaned runtimes

Next: Getting Help from Local Documentation