x11docker: Run GUI applications in Docker or podman containers.

Avoid X security leaks and enhance container security

Latest release is v7.8.0

Table of contents

• Introduction
  • Docker Desktop or Docker Engine
  • TL;DR
  • Features
  • Supported systems
• Terminal syntax
• Options
  • Choice of X servers and Wayland compositors
  • Desktop or seamless mode
  • Internet access
  • Shared folders and HOME in container
  • GPU hardware acceleration
  • Clipboard
  • Sound
  • Webcam
  • Printer
  • Language locales
  • Wayland
  • Init system
  • DBus
  • Container runtime
  • Backends other than docker
  • Preconfiguration with --preset
    • Default preset for all x11docker sessions
• Security
  • Security weaknesses
  • Options degrading container isolation
  • Sandbox
  • Security and feature check
• Installation
  • Installation from distribution repositories
  • Manual installation
    • Installation options
    • Installed files
    • Shortest way for first installation
    • Minimal installation
    • Installation on MS Windows
    • Deinstallation
• Dependencies
• Troubleshooting
  • Core checks
  • Privilege checks
  • Other checks
• Contact
  • Issues
  • Contributing
  • Support
• Donation
• Examples
  • Single applications
  • Desktop environments
  • Adjust images for your needs
  • Screenshots

Introduction

x11docker allows to run graphical desktop applications (and entire desktops) in Linux containers.

• Container tools like Docker and podman allow to run applications in an isolated container environment. Containers need much less resources than virtual machines for similar tasks.
• Docker and podman do not provide a display server that would allow to run applications with a graphical user interface.
• x11docker fills the gap. It runs an X display server and provides it to containers. X servers can run from host or in a container of image x11docker/xserver. x11docker supports Wayland as well.
• Additionally x11docker does some security setup to enhance container isolation and to avoid X security leaks. This allows a sandbox environment that fairly well protects the host system from possibly malicious or buggy software.

Software can be installed in a deployable image with a rudimentary Linux system inside. This can help to run or deploy software that is difficult to install on several systems due to dependency issues. It is possible to run outdated versions or latest development versions side by side. Files to work on can be shared between host and container.

x11docker wiki provides some how-to's for basic setups without x11docker.

Docker Desktop or Docker Engine

Since a while Docker distributes a version called "Docker Desktop" that runs Docker in a QEMU VM. x11docker support of this VM based version is experimental only and some features won't work; however, basic functionality is given. Instead, rather use x11docker with the native and more performant "Docker Engine Server version" that uses your host kernel to run containers.

• If you install Docker from your distribution's repository, you'll likely get this native version.
• The supported native Docker Engine package name is mostly docker.io or docker-ce, in opposite to the less supported VM based docker-desktop package.
• If you prefer podman over Docker, you don't need to care about this difference.

TL;DR

For a quick start:

• Install x11docker with:

  curl -fsSL https://raw.githubusercontent.com/mviereck/x11docker/master/x11docker | sudo bash -s -- --update
  

• Install dependencies:
  • Either pull image x11docker/xserver or install at least nxagent or xpra and xephyr.
• Run a GUI in container with:

  x11docker IMAGENAME [COMMAND]
  

• Add options:
  • --desktop for a desktop environment in image.
  • --gpu for hardware acceleration.
• Examples:

  x11docker x11docker/xfce thunar
  x11docker --desktop x11docker/xfce
  x11docker --gpu x11docker/xfce glxgears
  

Features

• Focus on security:
  • Avoids X security leaks by running additional X servers.
  • Restricts container capabilities to bare minimum.
  • Container user is same as host user to avoid root in container.
• Low dependencies:
  • No obliging dependencies on host beside X and one of docker or podman. Recommended: nxagent and Xephyr, alternatively image x11docker/xserver.
  • No dependencies inside of images except for some optional features.
• Several optional features like GPU, sound, webcam and printer support.
• Remote access with SSH, VNC or HTML5 possible.
• Easy to use. Examples:
  • x11docker x11docker/fvwm xterm
  • x11docker --desktop --size 320x240 x11docker/lxde (needs nested X server Xephyr)

Supported systems

x11docker runs on Linux and (with some setup and limitations) on MS Windows. x11docker does not run on macOS except in a Linux VM.

Terminal syntax

Just type x11docker IMAGENAME [COMMAND].

• Get an overview of options with x11docker --help.
  • For desktop environments in image add option -d, --desktop.
  • For internet access use option -I, --network.
  • To run without X at all use option -t, --tty.
  • Get an interactive TTY with option -i, --interactive.
  • See generated container backend command (and further infos) with option --debug.
• If startup fails, look at chapter Troubleshooting.

General syntax:

Usage:
To run a container on a new X server:
  x11docker IMAGE
  x11docker [OPTIONS] IMAGE [COMMAND]
  x11docker [OPTIONS] -- IMAGE [COMMAND [ARG1 ARG2 ...]]
  x11docker [OPTIONS] -- CUSTOM_RUN_OPTIONS -- IMAGE [COMMAND [ARG1 ARG2 ...]]
To run a host application on a new X server:
  x11docker [OPTIONS] --backend=host COMMAND
  x11docker [OPTIONS] --backend=host -- COMMAND [ARG1 ARG2 ...]
  x11docker [OPTIONS] --backend=host -- -- COMMAND [ARG1 ARG2 ...] -- [ARG3]
To run only an empty new X server:
  x11docker [OPTIONS] --xonly

CUSTOM_RUN_OPTIONS are just added to the docker|podman run command without a serious check by x11docker.

Options

Description of some commonly used feature options.

• Some of these options have dependencies on host and/or in image. Compare wiki: feature dependencies.
• For often used option combinations you can make shortcuts with option --preset.

Choice of X servers and Wayland compositors

If no X server option is specified, x11docker automatically chooses one depending on installed dependencies and on given or missing options --desktop, --gpu, --wayland and --xw. Most lightweight are nxagent and Xephyr.

• Overview of all possible X server and Wayland options.
  • Hints to use option --xorg within X.
• Indicate a desktop environment with option --desktop.
• Use option --wayland to get a Wayland environment.
• Use option --xw to run X and Wayland applications side by side.
• Use option -t, --tty to run without X or Wayland at all.

Desktop or seamless mode

x11docker assumes that you want to run a single application in seamless mode, i.e. a single window on your regular desktop. If you want to run a desktop environment in image, add option --desktop.

• Seamless mode is supported with options --nxagent and --xpra. As a fallback insecure option --hostdisplay is possible.
• Desktop mode with --desktop is supported with all X server options except --hostdisplay. If available, x11docker prefers --xephyr and --nxagent.
• Special case: Single applications with a window manager (option --wm).
  • If neither nxagent nor xpra are installed, but x11docker finds a desktop capable X server like Xephyr, it avoids insecure option --hostdisplay and runs Xephyr with a window manager.
• Running X and Wayland applications side by side is possible with --weston-xwayland --wayland, or, if running in a Wayland environment, with --hostdisplay --hostwayland.

Internet access

By default x11docker disables Network access for containers with --network=none because it targets best possible container isolation. To allow internet access set option -I or --network.

Shared folders, volumes and HOME in container

Changes in a running container system will be lost, the created container will be discarded. For persistent data storage you can share host directories or volumes:

• Option -m, --home creates a host directory in ~/.local/share/x11docker/IMAGENAME that is shared with the container and mounted as its HOME directory. Files in container home and user configuration changes will persist. x11docker creates a softlink from ~/.local/share/x11docker to ~/x11docker.
  • You can specify another host directory for container HOME with --home=DIR.
  • You can specify a volume for container HOME with --home=VOLUME.
• Option --share PATH mounts a host file or folder at the same location in container.
  • You can also specify a volume with --share VOLUME.
  • --share PATH:ro restricts to read-only access.
  • Device files in /dev are supported, too.
• Special cases for $HOME:
  • --home=$HOME will use your host home as container home. Discouraged, use with care.
  • --share $HOME will symlink your host home as a subfolder of container home.

Note that x11docker copies files from /etc/skel in container to HOME if HOME is empty. That allows to provide predefined user configurations in the image.

GPU hardware acceleration

Hardware acceleration for OpenGL is possible with option -g, --gpu.

• This will work out of the box in most cases with open source drivers on host. Otherwise have a look at wiki: feature dependencies.
• Closed source NVIDIA drivers need some setup and support less x11docker X server options for driver version < v470.x and Xwayland < v22.1.2.

Clipboard

Clipboard sharing is possible with option -c, --clipboard [=ARG].

• Optional argument cmv only provide host clipboard content to container if keys [CTRL][META][v] are pressed.
• Optional arguments c2h and h2c only transfers clipboard content from container to host or vice versa.
• Support of Wayland and X11 clipboards. Wayland windows might flicker due to focus issues with Wayland clipboard checks.

Sound

Sound is possible with options --pipewire, --pulseaudio and --alsa.

• For pipewire sound with --pipewire you need pipewire on host and pipewire in image. You likely also need pipewire-pulse and/or pipewire-alsa. Pipewire packages for jack are available, too. Compare wiki: feature dependencies.
  • Special case: If you have pipewire and pipewire-pulse on host and pulseaudio client libraries in image, --pulseaudio=tcp would work.
• For pulseaudio sound with --pulseaudio you need pulseaudio on host and pulseaudio (at least the pulseaudio client libraries) in image. Compare wiki: feature dependencies.
• For ALSA sound with --alsa you might need to specify a sound card with e.g. --alsa=Generic. Get a list of available sound cards with aplay -l.

Webcam

Webcams on host can be shared with option --webcam.

• If webcam application in image fails, install --gpu dependencies in image. Compare wiki: feature dependencies.
• guvcview needs --pulseaudio or --alsa.
• cheese and gnome-ring need --init=systemd.

Printer

Printers on host can be provided to container with option --printer.

• It needs cups on host, the default printer server for most linux distributions.
• The container needs cups client libraries in image. Compare wiki: feature dependencies.

Language locales

x11docker provides option --lang for flexible language locale settings.

• --lang without an argument sets LANG in container to same as on host. Same as --lang=$LANG
• x11docker will check on container startup if the desired locale is already present in image and enable it.
• If x11docker does not find the locale, it creates it on container startup. This needs some locale packages in image. Compare wiki: feature dependencies.
• Examples: --lang=de for German, --lang=zh_CN for Chinese, --lang=ru for Russian, --lang=$LANG for your host locale.
• For support of chinese, japanese and korean characters install a font like fonts-arphic-uming in image.
• Keyboard input methods like fcitx-pinyin are possible with some container setup. Compare ticket #269.

Wayland

To run Wayland instead of an X server x11docker provides options --wayland, --weston and --hostwayland. For further description loot at wiki: Description of Wayland options.

• Option --wayland automatically sets up a Wayland environment. It regards option --desktop.
• Options --weston runs Wayland compositor weston.
• Option --hostwayland can run applications seamless on host Wayland desktops like Gnome 3, KDE 5 and Sway.
• Example: xfce4-terminal on Wayland: x11docker --wayland x11docker/xfce xfce4-terminal

Init system

x11docker supports several init systems as PID 1 in container with option --init. Init in container solves the zombie reaping issue. As default x11docker uses tini in/usr/bin/docker-init. Also available are systemd, SysVinit, runit, OpenRC and s6-overlay. elogind is supported, too. Look at wiki: Init systems in Docker.

DBus

Some desktop environments and applications need a running DBus system daemon and/or DBus user session. DBus options need dbus in image.

• use --dbus to run a DBus user session daemon.
• A DBus system daemon will be started automatically with init systems systemd, openrc, runit and sysvinit (option --init).
  • It is also possible to run a DBus system daemon with --dbus=system without advanced init systems. However, this causes trouble in some cases and is not recommended in general.
• use --hostdbus to connect to host DBus user session.
• use --share /run/dbus/system_bus_socket to share host DBus system socket.

Container runtime

It is possible to run containers with different backends following the OCI runtime specification. Docker's default runtime is runc. You can specify another one with option --runtime=RUNTIME. Container runtimes known and supported by x11docker are:

• runc: Docker default.
• nvidia: Specialized fork of runc to support nvidia/nvidia-docker images.
• crun: Fast and lightweight alternative to runc with same functionality.
• oci: Runtime reported in #205, no documentation found. Handled by x11docker like runc.
• sysbox-runtime: Based on runc, aims to enhance container isolation. Support is experimental yet. Needs Sybox>=0.5.0 and kernel version >=5.12.

Using different runtimes is well tested for rootful Docker, but not for other backend setups.

Example: possible runtime configuration in /etc/docker/daemon.json:

{
  "default-runtime": "runc",
  "runtimes": {
    "crun": {
      "path": "/usr/local/bin/crun",
      "runtimeArgs": []
    },
    "nvidia": {
      "path": "nvidia-container-runtime",
      "runtimeArgs": []
    },
    "sysbox-runc": {
      "path": "/usr/bin/sysbox-runc"
    }
  }
}

Backends other than docker

x11docker supports container tools Docker and podman with option --backend=BACKEND in rootful and rootless mode. Supported --backend arguments: docker podman host

Container backends:

• By default x11docker tries to run docker.
  • To change the default --backend=docker to another one like --backend=podman, create a default file for --preset.
• Recommended for rootful container backend: docker or podman
• Recommended for rootless container backend: podman
  • Only podman allows option --home in rootless mode yet.
  • Only podman provides useful file ownerships with option --share in rootless mode yet.

Other supported backends that are in fact no containers:

• --backend=host runs a host application on a new X server. No containerization is involved.

Preconfiguration with --preset

For often used option combinations you might want to use option --preset FILENAME to have a command shortcut. FILENAME is a file in ~/.config/x11docker/preset or in /etc/x11docker/preset containing some x11docker options.

• Example multimedia: Create a file ~/.config/x11docker/preset/multimedia:

  --gpu
  --webcam
  --printer
  --pipewire
  --clipboard
  --share ~/Videos
  --share ~/Music
  

  Use it like: x11docker --preset=multimedia jess/vlc
• Example deepin desktop: Instead of long command

  x11docker --desktop --init=systemd --gpu --pulseaudio --home -- --cap-add=IPC_LOCK -- x11docker/deepin
  

  you can create a file ~/.config/x11docker/preset/deepin containing the desired options and even the image name:

  --desktop 
  --init=systemd
  --gpu
  --pulseaudio
  --home
  -- 
  --cap-add=IPC_LOCK
  -- 
  x11docker/deepin
  

  Run with: x11docker --preset=deepin

Default preset for all x11docker sessions

You can create a default preset file that is applied on all x11docker sessions. You can think of it as a configuration file for x11docker.

• Example: To always use podman instead of docker, create a file with name default in ~/.config/x11docker/preset or in /etc/x11docker/preset with content:

  --backend=podman
  

  This will cause x11docker to always use podman instead of docker unless specified otherwise in the x11docker command.

The same way you can specify other and more options as default, e.g. --homebasedir=/my/containerhome/path. Note that a local user default file will supersede a system wide default file.

Security

Scope of x11docker is to run containerized GUI applications while preserving and improving container isolation. Core concept is:

• Runs a second X server to avoid X security leaks.
  • This in opposite to widespread solutions that share host X socket of display :0, thus breaking container isolation, allowing keylogging and remote host control. (However, x11docker provides this with fallback option --hostdisplay).
  • Authentication is done with MIT-MAGIC-COOKIE, stored separate from file ~/.Xauthority.
• Creates container user similar to host user to avoid root in container.
  • You can also specify another user with --user=USERNAME or a non-existing one with --user=UID:GID.
  • Disables possible root password and deletes entries in /etc/sudoers.
    • If you want root permissions in container, use option --sudouser that allows su and sudo with password x11docker.
  • If you want to use USER specified in image instead, set option --user=RETAIN. x11docker won't change container's /etc/passwd or /etc/sudoers in that case. Option --home won't be available.
• Reduces container capabilities to bare minimum.
  • Sets run option --cap-drop=ALL to drop all capabilities. Most applications don't need them.
  • Sets run option --security-opt=no-new-privileges.
  • These restrictions can be disabled with x11docker option --cap-default or reduced with --sudouser, --newprivileges.

That being said, the default docker capabilities and the seccomp/SELinux/apparmor profiles are set up well to protect the host system. Nonetheless, x11docker follows the principle of least privilege. Containers should not have capabilities or privileges that they don't need for their job.

Security weaknesses

• Possible SELinux restrictions are degraded for x11docker containers with run option --security-opt label=type:container_runtime_t to allow access to new X unix socket. A more restrictive solution is desirable. Compare: SELinux and Docker: allow access to X unix socket in /tmp/.X11-unix
• A possible user namespace remapping setup is disabled to allow options --home and --share without file ownership issues.
  • This is less an issue because x11docker already avoids root in container.
  • Exception: User namespace remapping is not disabled for --user=RETAIN.
• x11docker provides several different X server options. Each X server involved might have its individual vulnerabilities. x11docker only covers well-known X security leaks that result from X11 protocol design.
  • An additional security layer for most supported X servers is set up if image x11docker/xserver is available. It will be used automatically in most cases if available. Enforce its usage with option --xc=yes.

Options degrading container isolation

x11docker shows warning messages in terminal if chosen options degrade container isolation. Note that x11docker does not check custom DOCKER_RUN_OPTIONS.

Most important:

• --hostdisplay shares host X socket of display :0 instead of running a second X server.
  • Danger of abuse is reduced providing so-called untrusted cookies, but do not rely on this.
  • If additionally using --gpu or --clipboard, option --ipc=host and trusted cookies are enabled and no protection against X security leaks is left.
  • If you don't care about container isolation, x11docker --hostdisplay --gpu is an insecure but quite fast setup without any overhead.
• --gpu allows access to GPU hardware. This can be abused to get window content from host (palinopsia bug) and makes GPU rootkits like keyloggers possible.
• --pipewire, --pulseaudio and --alsa allow catching audio output and microphone input from host.

Rather special options reducing security, but not needed for regular use:

• --sudouser allows su and sudo with password x11dockerfor container user. If an application somehow breaks out of container, it can harm your host system. Allows many container capabilities that x11docker would drop otherwise.
• --cap-default disables x11docker's container security hardening and falls back to default container capabilities as provided by the backends docker or podman. If an application somehow breaks out of container, it can harm your host system.
• --init=systemd|sysvinit|openrc|runit allow some container capabilities that x11docker would drop otherwise. --init=systemd also shares access to /sys/fs/cgroup. Some processes will run as root in container. If a root process somehow breaks out of container, it can harm your host system. Allows many container capabilities that x11docker would drop otherwise.
• --hostdbus allows communication over DBus with host applications.

Sandbox

Container isolation enhanced with x11docker allows to use containers as a sandbox that fairly well protects the host system from possibly malicious or buggy software. Though, no sandbox solution in the wild can provide a perfect secure protection, and Docker even with enhanced security settings from x11docker is no exception.

Using x11docker as a sandbox is not intended to run obviously evil software. Rather use it as:

• Compatibility environment to run software that is hard or impossible to install on host due to dependency issues.
• Development environment to collect libraries, compiler and so on to keep the host clean.
• Development environment to mitigate damage caused by unexpected/buggy behaviour.
• Security layer for software that may be malicious in worst case. Examples: Internet browser with enabled javascript, or wine with MS Windows applications.

x11docker already restricts process capabilities. You can additionally restrict access to CPU and RAM with option --limit. As default --limit restricts to 50% of available CPUs and 50% of currently free RAM. Another amount can be specified with --limit=FACTOR with a FACTOR greater than zero and less than or equal one.

For more custom fine tuning have a look at Docker documentation: Limit a container's resources.

WARNING: There is no restriction that can prevent the container from flooding the hard disk storing the container or in shared folders.

Security and feature check

To check container isolation and some feature options use image x11docker/check and try out with several options.

• An insecure setup is x11docker --hostdisplay --gpu x11docker/check. It fairly well demonstrates common X security leaks.
• Add options like --pulseaudio --alsa --webcam --clipboard --printer to check their functionality.

Installation

Note that x11docker is just a bash script without library dependencies. Basically it is just a wrapper for X servers and container backends docker and podman. To allow advanced usage of x11docker abilities have a look at chapter Dependencies.

Installation from distribution repositories

x11docker is available as a package in some distributions.

Much thanks to the maintainers who decided to provide these packages! There are some hints for packaging x11docker in the wiki.

Stable releases: Latest release is v7.8.0 . The following badges need some time to refresh.

Latest git master/beta version:

Manual installation

Installation options

As root you can install, update and remove x11docker in system directories to be available system-wide:

• x11docker --install : install x11docker from current directory. (Useful to install from an extracted zip file or a cloned git repository.)
• x11docker --update : download and install latest release from github.
• x11docker --update-master : download and install latest master version from github.
• x11docker --remove : remove all files installed by x11docker.
  • Note: This does not remove ~/.local/share/x11docker where it stores persistent files of option --home.
• x11docker --remove-oldprefix : Before version 7.6.0 x11docker installed itself into /usr/bin. Now it installs into /usr/local/bin. Use --remove-oldprefix to remove /usr/bin installations.

To see the difference between current and coming updated version, you can use optional argument diff for --update and --update-master. Example: x11docker --update-master=diff will show you the code changes from your current installation to latest master/beta version without installing it.

Installed files

What the installation does (just for information):

• Copies script x11docker to /usr/local/bin.
• Installs icon x11docker.png below /usr/share/icons using xdg-icon-resource.
• Copies documentation README.md, CHANGELOG.md and LICENSE.txt to /usr/local/share/doc/x11docker.
• Stores man page for x11docker in /usr/local/share/man/man1/x11docker.1.gz.

Shortest way for first installation:

• For systems using sudo:

  curl -fsSL https://raw.githubusercontent.com/mviereck/x11docker/master/x11docker | sudo bash -s -- --update
  

• Directly as root:

  curl -fsSL https://raw.githubusercontent.com/mviereck/x11docker/master/x11docker | bash -s -- --update
  

Minimal installation

You can run x11docker from an arbitrary location with bash x11docker or ./x11docker. For minimal system-wide installation make x11docker executable with chmod +x x11docker and move it to /usr/local/bin (or another location in PATH). Other files than script x11docker itself are not essential.

Installation on MS Windows

x11docker can run natively on MS Windows electively in one of:

• WSL (Windows subsystem for Linux)
• Cygwin
• MSYS2

Further information at wiki: x11docker on MS Windows.

Deinstallation

You can remove x11docker with x11docker --remove. That will remove the files listed above. It will also remove ~/.cache/x11docker and stop all running x11docker containers. x11docker will not remove:

• Files and folders for persistent data storage with option --home. These are:
  • ~/.local/share/x11docker where persistent data is stored.
  • Softlink ~/x11docker that points there.
• Folders you might have created yourself for x11docker:
  • ~/.local/share/x11docker
  • ~/.config/x11docker

Dependencies

x11docker can run with standard system utilities without additional dependencies on host or in image.

• As a core it only needs bash and one of docker or podman or to run containers on X.
• x11docker also needs an X server. x11docker can automatically use image x11docker/xserver that provides most optional x11docker dependencies and several X servers and Wayland compositors so you won't need to install them on host.
  • If you prefer to install dependencies on host:
    • The recommended base commands are: nxagent Xephyr weston Xwayland xdotool xauth xinit xclip xhost xrandr xdpyinfo. Some of them are probably already installed.
    • See wiki: Dependencies - Recommended base for a package list matching your distribution.

Dependencies in image:

• Some feature options have additional dependencies on host and/or in image. This affects especially options --gpu, --printer, --pipewire and --pulseaudio.
• Compare wiki: feature dependencies.

Troubleshooting

For troubleshooting run x11docker in a terminal. x11docker shows warnings if something is insecure, missing or going wrong. Also it shows notes if options don't work and fallbacks are used. It might give hints to fix some issues.

Core checks

1. Make sure your x11docker version is up to date with x11docker --update (latest release) or x11docker --update-master (latest beta).

2. Carefully read the regular x11docker messages. Often they already give a hint what to do.

• Use option -D, --debug to see some internal messages.
• Use option -v, --verbose to see full logfile output.
• You can find the latest dispatched logfile at ~/.cache/x11docker/x11docker.log.

3. Try another X server option.

• Some applications fail with fallback option --hostdisplay. Add --clipboard to disable some security restrictions of --hostdisplay.
• If that does not help, install additional X servers. The most stable and reliable option is --xephyr.

Privilege checks

Some applications need more privileges or capabilities than x11docker provides by default. One attempt is to allow several privileges until the setup works. Than reduce privileges to find out which are needed indeed. (Note the -- in the following commands, do not miss them).

1. Adding privileges:

• Try x11docker --cap-default IMAGENAME
• Try x11docker --cap-default --ipc=host --network=host IMAGENAME
• Try x11docker --cap-default --ipc=host --network=host --share /run/udev/data:ro -- --cap-add ALL --security-opt seccomp=unconfined --security-opt apparmor=unconfined --privileged -- IMAGENAME

2. Reducing privileges:

• Drop options one by one in this order: --privileged --security-opt apparmor=unconfined --security-opt seccomp=unconfined --cap-add ALL --share /run/udev/data:ro --network=host --ipc=host --cap-default. Only leave options that are needed to keep the setup working.
• Option --cap-default might already be enough. It allows default container capabilities as docker|podman would do on themself.
  • You can just stop debugging and reducing here if you like to.
  • You can try to reduce --cap-default. Partially remove additional options to find out which one(s) are needed:
    • First try x11docker --newprivileges -- IMAGENAME
    • Than try and reduce: x11docker --newprivileges -- --cap-add=SETPCAP --cap-add=MKNOD --cap-add=AUDIT_WRITE --cap-add=CHOWN --cap-add=NET_RAW --cap-add=DAC_OVERRIDE --cap-add=FOWNER --cap-add=FSETID --cap-add=KILL --cap-add=SETGID --cap-add=SETUID --cap-add=NET_BIND_SERVICE --cap-add=SYS_CHROOT --cap-add=SETFCAP -- IMAGENAME
• --cap-add ALL should not be considered to be a solution.
  • Drop capabilities from following command to find the one(s) you need: x11docker --cap-default -- --cap-add=SYS_MODULE --cap-add=SYS_RAWIO --cap-add=SYS_PACCT --cap-add=SYS_ADMIN --cap-add=SYS_NICE --cap-add=SYS_RESOURCE --cap-add=SYS_TIME --cap-add=SYS_TTY_CONFIG --cap-add=AUDIT_CONTROL --cap-add=MAC_OVERRIDE --cap-add=MAC_ADMIN --cap-add=NET_ADMIN --cap-add=SYSLOG --cap-add=DAC_READ_SEARCH --cap-add=LINUX_IMMUTABLE --cap-add=NET_BROADCAST --cap-add=IPC_LOCK --cap-add=IPC_OWNER --cap-add=SYS_PTRACE --cap-add=SYS_BOOT --cap-add=LEASE --cap-add=WAKE_ALARM --cap-add=BLOCK_SUSPEND --cap-add=AUDIT_READ -- IMAGENAME
  • Many of these capabilities are rather dangerous and should not be allowed for a container. Especially to mention is SYS_ADMIN.
• Option --privileged should not be considered to be a solution. Basically it allows arbitrary access to the host for container applications.
  • Likely you need to share a device file in /dev, e.g. something like --share /dev/vboxdrv.
• --ipc=host and --network=host severely reduce container isolation. Better solutions are desirable.

3. Open a ticket to ask for possibilities how to optimize the privilege setup.

Other checks

1. Container user: By default x11docker sets up an unprivileged container user similar to your host user.

• The image may have a USER specification and be designed for this user.
  • Check for a USER specification in image with docker inspect --format '{{.Config.User}}' IMAGENAME
  • You can enable this predefined user with --user=RETAIN
• The container might need a root user. Try with --user=root, maybe add --cap-default.

2. Init and DBus

• A few applications need a DBus user daemon. Install dbus in image and try option --dbus.
• A few applications need systemd and/or a running DBus system daemon. Install systemd in image and try option --init=systemd.

3. Architecture check of host OS and image

• The image may not be built for the architecture of your host OS. (ie. Image is built for amd64 but your OS runs on arm, e.g. on a RaspBerry PI). With a mismatch the container will quit unexpectedly & x11docker may emit the error dockerrc(): Did not receive PID of PID1 in container.
  • You can check the image architecture with docker inspect --format {{.Architecture}} IMAGENAME.
  • You can check the host architecture with uname -m.
  • For further information and multi-arch setups look at wiki: Multi-arch setups with QEMU.

Contact

Feel free to open a ticket if you have a question or encounter an issue.

Issues

If reporting an issue:

• Have a look at chapter Troubleshooting.
• Most times it makes sense to store the --verbose output (or ~/.cache/x11docker/x11docker.log) at pastebin.com.
  • Personal information in the logfile is mainly the user name (also in paths) and some hardware and system information.

Contributing

If you want to contribute to x11docker, please open a ticket before creating a pull request. Often it is possible to accomplish desired tasks with already available options. Note that x11docker is considered to be stable and changes other than bug fixes are less likely to be merged. In general new features are not intended.

Support

Please open a ticket if you need support. Please note that x11docker is a non-commercial project maintained in free time. I'll help where I can, but there is no organisation behind x11docker that can provide large scale support.

Donation

If you like to make a donation: Thank you! :) Please have a look at my sponsor site.

Instead of sponsoring me, you can as well spend some money to Galsan Tschinag in Mongolia (Wikipedia). One of his great projects is the afforestation of Mongolia. A donation account in Germany is provided by Förderverein Mongolei e.V..

Förderverein Mongolei e.V.
IBAN DE7261290120 0394 3660 00
BIC GENODES1NUE
Volksbank Kirchheim-Nürtingen

I personally know some of the people behind this. I assure that they are trustworthy and have a great heart and soul and do a good thing.

Examples

Some x11docker image examples with desktop environments can be found on docker hub. A special one to check features and container isolation is x11docker/check.

Docker does not provide automated builds for free anymore, so the images are becoming outdated. Instead of pulling them, rather build them locally with x11docker option --build.

Some x11docker Dockerfiles are provided at https://github.com/mviereck?tab=repositories; look for repositories beginning with dockerfile-x11docker. You can build locally from these Dockerfiles with x11docker option --build. Example:

x11docker --build x11docker/fvwm

Single applications

Desktop environments

Adjust images for your needs

For persistent changes of image system adjust Dockerfile and rebuild. To add custom applications to x11docker example images you can create a new Dockerfile based on them. Example:

# xfce desktop with VLC media player
FROM x11docker/xfce
RUN apt-get update && apt-get install -y vlc

Screenshots

More screenshots are stored in screenshot branch

x11docker --desktop x11docker/lxqt

x11docker --desktop x11docker/lxde-wine

x11docker --desktop --gpu --init=systemd -- --cap-add=IPC_LOCK --security-opt seccomp=unconfined -- x11docker/deepin