Flatpak

From the project README: "Flatpak is a system for building, distributing and running sandboxed desktop applications on Linux."

From flatpak(1):

Flatpak is a tool for managing applications and the runtimes they use. In the Flatpak model, applications can be built and distributed independently from the host system they are used on, and they are isolated from the host system ('sandboxed') to some degree, at runtime.

Flatpak uses OSTree to distribute and deploy data. The repositories it uses are OSTree repositories and can be manipulated with the ostree utility. Installed runtimes and applications are OSTree checkouts.

Warning:

Many Flatpak applications available on flathub are not effectively sandboxed by default [1]. Do not rely on the provided process isolation without first reviewing the related flatpak permission manifest for common sandbox escape issues.
Running untrusted code is never safe; sandboxing cannot change this.

Installation

Install the flatpak package. If you want to build flatpaks, install flatpak-builder too.

Desktop integration

For flatpak applications to interact with your desktop (i.e. allow applications to open URLs, share your screen and more), make sure to set up the xdg-desktop-portal. Depending on the implementation for your desktop, there is a confirmation dialog before the application is able to access some portals.

Application management

Discover — KDE frontend to Flatpak which helps you find and install applications, games, and tools. Part of plasma.

https://apps.kde.org/discover/ || discover

GNOME Software — GNOME frontend to Flatpak which lets you install and update applications and system extensions. Part of gnome.

https://apps.gnome.org/Software/ || gnome-software

Permission management

Flatpak Permissions Management KCM — KDE Configuration Module that allows changing what permissions have been granted to installed Flatpak applications. Part of plasma.

https://invent.kde.org/plasma/flatpak-kcm || flatpak-kcm

Flatseal — Graphical utility to review and modify permissions from your Flatpak applications.

https://github.com/tchx84/Flatseal || flatseal^AUR

malcontent (Parental Controls) — Implements support for restricting the type of content accessible to non-administrator accounts. Part of gnome.

https://gitlab.freedesktop.org/pwithnall/malcontent || malcontent

Managing repositories

Note: By default, every flatpak command works system-wide, i.e. packages are installed for all users of the computer; also by default, flatpak requires the user to supply the root password. To install packages and work with repositories for a single user (with no need of superuser rights) you can add the option --user to each command. If you want, for example, to add a repository only visible to you, you should execute flatpak remote-add --user name location.

Add a repository

To add a remote flatpak repository do:

$ flatpak remote-add name location

where name is the name for the new remote, and location is the path or URL for the repository.

The installation of flatpak will, by default, add the official Flathub repository as a system-wide installation. To add the official repository with a per-user configuration:

$ flatpak remote-add --if-not-exists --user flathub https://dl.flathub.org/repo/flathub.flatpakrepo

Delete a repository

To delete a remote flatpak repository do:

$ flatpak remote-delete name

where name is the name of the remote repository to be deleted.

List repositories

To list all the added repositories do:

$ flatpak remotes

Managing runtimes and applications

Note: If remotes have been added with a per-user configuration, the --user option can be appended to the following flatpak commands. For example, to install a package visible only to you, run flatpak install --user package-name.

Search for a remote runtime or application

Before being able to search for a runtime or application in a newly added remote repository, we need to retrieve the appstream data for it:

$ flatpak update

Looking for updates...
Updating appstream data for remote name

Then we can proceed to search for a package with flatpak search packagename, e.g. to look for the package libreoffice with the flathub remote configured:

$ flatpak search libreoffice

Application ID              Version Branch Remotes Description                       
org.libreoffice.LibreOffice         stable flathub The LibreOffice productivity suite

List all available runtimes and applications

To list all available runtimes and applications in a remote repository named remote do:

$ flatpak remote-ls remote

Install a runtime or application

To install a runtime or application do:

$ flatpak install remote name

where remote is the name of the remote repository, and name is the name of the application or runtime to install.

Tip: You can use partial identifiers flatpak install partial-name (for example flatpak install libreoffice).

List installed runtimes and applications

To list installed runtimes and applications do:

$ flatpak list

Run applications

Binaries are available in /var/lib/flatpak/exports/bin, which is automatically added to $PATH by /etc/profile.d/flatpak-bindir.sh. You may have to re-login to apply the change.

Flatpak applications can also be run with the command line:

$ flatpak run name

Update a runtime or application

List runtimes and applications that have updates available:

$ flatpak remote-ls --updates

To update a runtime or application named name do:

$ flatpak update name

To update all applications and runtimes:

$ flatpak update

Automatic updates via systemd

Warning: It is generally not a good idea to run unattended updates via systemd, as the applications can get new permissions without the user aware of the changes. See this blogpost for examples.

To update your system runtimes and applications automatically, create the following files:

/etc/systemd/system/flatpak-update.service

[Unit]
Description=Update Flatpak
After=network-online.target
Wants=network-online.target

[Service]
Type=oneshot
ExecStart=/usr/bin/flatpak update --noninteractive --assumeyes

[Install]
WantedBy=multi-user.target

/etc/systemd/system/flatpak-update.timer

[Unit]
Description=Update Flatpak

[Timer]
OnBootSec=2m
OnActiveSec=2m
OnUnitInactiveSec=24h
OnUnitActiveSec=24h
AccuracySec=1h
RandomizedDelaySec=10m

[Install]
WantedBy=timers.target

Afterwards, do a daemon-reload and enable/start the flatpak-update.timer unit.

Note:

This guide is for system flatpak installations which are the default in flatpak. For user flatpak installations:
- Create the above files in the /etc/systemd/user/ directory.
- Add the --user flag in ExecStart line in flatpak-update.service.
- Run the systemctl commands with the --user flag.

Uninstall a runtime or application

To uninstall a runtime or application named name do:

$ flatpak uninstall name

To delete app data from ~/.var/app and from the permission store while uninstalling, use:

$ flatpak uninstall --delete-data name

Tip: You can uninstall unused flatpak "refs" (aka orphans with no application/runtime) with flatpak uninstall --unused.

Downgrade a runtime or application

To downgrade a runtime or application, first look for the associated commit ID:

$ flatpak remote-info --log remote name

Where remote is the repository (such as flathub), and name is the name of the application or runtime. Then, deploy the commit:

$ flatpak update --commit=commit name

where commit is the commit for the desired version, and name is as before.

This procedure can also be used to selectively upgrade a package to a desired version that is not the latest version.

To exclude flatpak update from updating this package, see #Prevent updates to a runtime or application.

Prevent updates to a runtime or application

To prevent automatic and manual updates to a runtime or application, use the flatpak mask command:

$ flatpak mask name

This also prevents selective upgrades and downgrades.

To reverse the mask and re-enable updates, use flatpak mask --remove:

$ flatpak mask --remove name

Add Flatpak .desktop files to your menu

Flatpak expects window managers to respect the XDG_DATA_DIRS environment variable to discover applications. This variable is set by the script /etc/profile.d/flatpak.sh. Updating the environment may require restarting the session. If the launcher does not support XDG_DATA_DIRS, you can edit the list of directories scanned and add these to it:

~/.local/share/flatpak/exports/share/applications
/var/lib/flatpak/exports/share/applications

This is known to be necessary in Awesome.

View sandbox permissions of application

Flatpak applications come with predefined sandbox rules which define the resources and file system paths the application is allowed to access. To view the specific application permissions do:

$ flatpak info --show-permissions name

The reference of the sandbox permission names can be found on official flatpak documentation.

Override sandbox permissions of applications

If you find the predefined permissions of the application too lax or too restrictive you can change to anything you want using flatpak override command. For example:

$ flatpak override --nofilesystem=home name

This will prevent the application access to your home folder.

Every type of permission, such as device, filesystem or socket, has a command line option that allows that particular permission and a separate option that denies permission. For example, in case of device access --device=device_name allows access, --nodevice=device_name denies the permission to access device.

For all permission types commands consult the manual page: flatpak-override(1)

Permission overrides can be reset to defaults with command:

$ flatpak override --reset name

Flatseal is a GUI permissions manager which offers simple point-and-click permissions operations. In KDE Plasma, Flatpak Permissions Management KCM provides a similiar GUI for the system settings application: System Settings > Applications > Flatpak Permission Settings.

Creating a custom base runtime

This article or section needs expansion.

Reason: This can certainly be improved. It also has problems with D-Bus for GNOME apps. (Discuss in Talk:Flatpak)

Warning: If you want to release your software to the public as a Flatpak, an Arch-based runtime is unsuitable. In this case, you will want to follow official documentation to integrate your software into the proper Flatpak ecosystem using the common runtimes.

Note:

You may want to use an untrusted, unprivileged user account for bundling untrusted software because the software is not sandboxed during app and runtime creation.
When distributing bundles to others, you may be legally obliged to provide the source code of some of the bundled software upon request. You may want to use ABS to build these packages from source.

You can create a custom Arch-based base runtime and base SDK for Flatpak using pacman. You can then use it for building and packaging applications. This is an alternative for personal use to the default org.freedesktop.BasePlatform and org.freedesktop.BaseSdk runtimes.

In addition to flatpak, you need to have installed fakeroot and for pacman hooks support also fakechroot.

First, start by creating a directory for building the runtime and possibly applications.

$ mkdir myflatpakbuilddir
$ cd myflatpakbuilddir

You can then prepare a directory for building the runtime base platform. The files subdirectory will contain what will later be the /usr directory in the sandbox. Therefore you will need to create symbolic links so the default /usr/share etc. from Arch can still be accessed at the usual path.

$ mkdir -p myruntime/files/var/lib/pacman
$ touch myruntime/files/.ref
$ ln -s /usr/usr/share myruntime/files/share
$ ln -s /usr/usr/include myruntime/files/include
$ ln -s /usr/usr/local myruntime/files/local

Make your host OS fonts available to the Arch runtime:

$ mkdir -p myruntime/files/usr/share/fonts
$ ln -s /run/host/fonts myruntime/files/usr/share/fonts/flatpakhostfonts

You need and may want to adapt your pacman.conf before installing packages to the runtime. Copy /etc/pacman.conf to your build directory and then make the following changes:

Remove the CheckSpace option so pacman will not complain about errors finding the root filesystem for checking disk space.
Remove any undesired custom repositories and IgnorePkg, IgnoreGroup, NoUpgrade and NoExtract settings that are needed only for the host system.

Now install the packages for the runtime.

$ fakechroot fakeroot pacman -Syu --root myruntime/files --dbpath myruntime/files/var/lib/pacman --config pacman.conf base
$ mv pacman.conf myruntime/files/etc/pacman.conf

Set up the locales to be used by editing myruntime/files/etc/locale.gen. Then regenerate the runtime’s locales.

$ fakechroot chroot myruntime/files locale-gen

The base SDK can be created from the base runtime with added applications needed for building packages and running pacman.

$ cp -r myruntime mysdk
$ fakechroot fakeroot pacman -S --root mysdk/files --dbpath mysdk/files/var/lib/pacman --config mysdk/files/etc/pacman.conf base-devel fakeroot fakechroot --needed

Insert metadata about runtime and SDK.

myruntime/metadata

[Runtime]
name=org.mydomain.BasePlatform
runtime=org.mydomain.BasePlatform/x86_64/2016-06-26
sdk=org.mydomain.BaseSdk/x86_64/2016-06-26

mysdk/metadata

[Runtime]
name=org.mydomain.BaseSdk
runtime=org.mydomain.BasePlatform/x86_64/2016-06-26
sdk=org.mydomain.BaseSdk/x86_64/2016-06-26

Add base runtime and SDK to a local repository in the current directory. You may want to give them appropriate commit messages such as “My Arch base runtime” and “My Arch base SDK”.

$ ostree init --mode archive-z2 --repo=.
$ EDITOR="nano -w" ostree commit -b runtime/org.mydomain.BasePlatform/x86_64/2016-06-26 --tree=dir=myruntime
$ EDITOR="nano -w" ostree commit -b runtime/org.mydomain.BaseSdk/x86_64/2016-06-26 --tree=dir=mysdk
$ ostree summary -u

Install the runtime and SDK.

$ flatpak remote-add --user --no-gpg-verify myarchos file://$(pwd)
$ flatpak install --user myarchos org.mydomain.BasePlatform 2016-06-26
$ flatpak install --user myarchos org.mydomain.BaseSdk 2016-06-26

Creating apps with pacman

As an alternative to building applications the usual way, we can use pacman to create a containerized version of the regular Arch packages. Note that /usr is read-only when creating apps, so we can not use Arch’s packages when building an app. To create a real app with pacman, we can either

use pacman to create a runtime containing all dependencies
and compile the app ourselves as usual or perhaps using pacman with a custom PKGBUILD tailored to Flatpak which uses --prefix=/app for the configure script,

or we can

use pacman to create a runtime containing the app installed with pacman
and create a dummy app to launch it.

For doing the latter, first create a runtime using pacman such as this one for gedit. The runtime is first initialized and prepared for use with pacman.

$ flatpak build-init -w geditruntime org.mydomain.geditruntime org.mydomain.BaseSdk org.mydomain.BasePlatform 2016-06-26
$ flatpak build geditruntime sed -i "s/^#Server/Server/g" /etc/pacman.d/mirrorlist
$ flatpak build geditruntime ln -s /usr/var/lib /var/lib
$ flatpak build geditruntime fakeroot pacman-key --init
$ flatpak build geditruntime fakeroot pacman-key --populate

Then the package is installed. The host’s network connection must be made available to pacman.

$ flatpak build --share=network geditruntime fakechroot fakeroot pacman --root /usr -S gedit

You can test the installation before finishing the runtime (without proper sandboxing).

$ flatpak build --socket=x11 geditruntime gedit

Now finish building the runtime and export it to a new local repository. pacman’s GnuPG keys have permissions that may interfere and need to be removed first.

$ flatpak build geditruntime rm -r /etc/pacman.d/gnupg
$ flatpak build-finish geditruntime
$ sed -i "s/\[Application\]/\[Runtime\]/;s/runtime=org.mydomain.BasePlatform/runtime=org.mydomain.geditruntime/" geditruntime/metadata
$ flatpak build-export -r geditrepo geditruntime

Then create a dummy app.

$ flatpak build-init geditapp org.gnome.gedit org.mydomain.BaseSdk org.mydomain.geditruntime

Now finish the dummy app. You can fine-tune the app’s access permissions when sandboxed by giving additional options when finishing the build. For possible options see the Flatpak documentation and the GNOME manifest files. Alternatively, adapt geditapp/metadata to your needs after finishing the build but before exporting. When the metadata file is complete, export the app to the repository.

$ flatpak build-finish geditapp --socket=x11 [possibly other options] --command=gedit
$ flatpak build-export geditrepo geditapp

Install it along with the runtime.

$ flatpak --user remote-add --no-gpg-verify geditrepo geditrepo
$ flatpak install --user geditrepo org.mydomain.geditruntime
$ flatpak install --user geditrepo org.gnome.gedit
$ flatpak run org.gnome.gedit

Troubleshooting

Flatpak does not run on the linux-hardened kernel

The linux-hardened kernel sets kernel.unprivileged_userns_clone to 0, so only privileged users can create new user namespaces.

One method to fix this is to install bubblewrap-suid. This package provides a version of bwrap(1) with the setuid bit enabled, allowing bubblewrap elevate itself and create new namespaces.

Alternatively, set kernel.unprivileged_userns_clone to 1 using sysctl(8), allowing unprivileged users to create new user namespaces:

# sysctl kernel.unprivileged_userns_clone=1

Warning: Using this kernel parameter value has negative security implications. See Security#Sandboxing applications for further information.

To make this change persist across reboots, add a configuration file to sysctl.d(5):

/etc/sysctl.d/flatpak.conf

kernel.unprivileged_userns_clone=1

For more information, see the note in Bubblewrap#Installation.

Failed to connect to Wayland display

If you the application doesn't properly open and you get messages such as Failed to connect to Wayland display: No such file or directory on flatpak run: This may be because some other setting such as ELECTRON_OZONE_PLATFORM_HINT="auto" makes the Flatpak application choose Wayland while access to Wayland isn't whitelisted for this application.

This can be fixed by whitelisting access to socket=wayland with e.g. Flatseal.

xdg-desktop-portal is failing to start

If you are starting X with manually-configured run commands, ensure you are including all essential components of the reference `xinitrc`. One of which sources a script which runs an update of the environment used for D-Bus session services.

systemctl --user import-environment DISPLAY XAUTHORITY
if command -v dbus-update-activation-environment >/dev/null 2>&1; then
   dbus-update-activation-environment DISPLAY XAUTHORITY
fi

Flatpak applications not picking up the default system theme

There is no ideal way to apply system themes in flatpak apps as mentioned in the flatpak documentation [2] [3]. The easiest solution is using themes that are available in Flathub. However there is a workaround which can be used to apply themes to your flatpak apps. stylepak-git^AUR automates this workaround.

"File not found" error when Open local HTML pages in Firefox

By default, the Flatpak version of Firefox will display a "File not found" error page when opening a local HTML. This is because permission must be granted to the app for accessing the folder containing the file.

However, note that when granting permission to access the entire Home folder, Firefox will then check for an existing profile in ~/.mozilla and load it instead of those previously in use from the sandboxed folder ~/.var/app/org.mozilla.firefox/cache/mozilla/. If your previous session's tabs and browsing history is missing after changing a permission (e.g. with Flatseal), either modify the permission to exclude access to ~/.mozilla, or consider copying the profile from ~/.var/app/org.mozilla.firefox/cache/mozilla/ to ~/.mozilla.

Links fail to open on wlroots-based compositors

Flatpak applications that attempt to open URIs make use of the org.freedesktop.portal.OpenURI.OpenURI D-Bus interface exposed by xdg-desktop-portal. The xdg-desktop-portal-wlr backend does not support this call and therefore you will need an additional backend to fill the gap, for example xdg-desktop-portal-gtk.

Applications do not use the correct cursor theme

There is no single standard to set the cursor properly. Some programs only need read access to the cursors directory, others also rely on other mechanisms. For GTK applications, ensure that xdg-desktop-portal-gtk is installed.

Otherwise, the following overrides should work for most common desktop applications.

$ flatpak -u override --filesystem=/usr/share/icons/:ro
$ flatpak -u override --filesystem=/home/$USER/.icons/:ro 
$ flatpak -u override --filesystem=xdg-config/gtk-3.0:ro
$ flatpak -u override --env=XCURSOR_PATH=~/.icons

In some cases you may also need to override the environment variables XCURSOR_THEME and XCURSOR_SIZE:

$ flatpak -u override --env=XCURSOR_THEME=Adwaita
$ flatpak -u override --env=XCURSOR_SIZE=24

See this discussion for additional details.

Flatpak Qt applications do not use Gnome Adwaita dark theme

If you switched your theme to Adwaita-dark and Flatpak Qt applications still use the light version, install the required KStyle:

# flatpak install flathub org.kde.KStyle.Adwaita