Docker container for Firefox

This is a Docker container for Firefox.

The GUI of the application is accessed through a modern web browser (no installation or configuration needed on the client side) or via any VNC client.

Mozilla Firefox is a free and open-source web browser developed by Mozilla Foundation and its subsidiary, Mozilla Corporation.

Table of Content

Docker container for Firefox

Quick Start

NOTE: The Docker command provided in this quick start is given as an example and parameters should be adjusted to your need.

Launch the Firefox docker container with the following command:

docker run -d \
    --name=firefox \
    -p 5800:5800 \
    -v /docker/appdata/firefox:/config:rw \
    --shm-size 2g \
    jlesage/firefox

Where:

/docker/appdata/firefox: This is where the application stores its configuration, log and any files needing persistency.

Browse to http://your-host-ip:5800 to access the Firefox GUI.

Usage

docker run [-d] \
    --name=firefox \
    [-e <VARIABLE_NAME>=<VALUE>]... \
    [-v <HOST_DIR>:<CONTAINER_DIR>[:PERMISSIONS]]... \
    [-p <HOST_PORT>:<CONTAINER_PORT>]... \
    --shm-size VALUE \
    jlesage/firefox

Parameter	Description
-d	Run the container in the background. If not set, the container runs in the foreground.
-e	Pass an environment variable to the container. See the Environment Variables section for more details.
-v	Set a volume mapping (allows to share a folder/file between the host and the container). See the Data Volumes section for more details.
-p	Set a network port mapping (exposes an internal container port to the host). See the Ports section for more details.
--shm-size	Set the size of `/dev/shm` to `VALUE`. The format of `VALUE` is `<number><unit>`, where `number` must be greater than `0` and `unit` can be `b` (bytes), `k` (kilobytes), `m` (megabytes), or `g` (gigabytes). NOTE: To avoid crashes, it is recommended to set this value to `2g`.

Environment Variables

To customize some properties of the container, the following environment variables can be passed via the -e parameter (one for each variable). Value of this parameter has the format <VARIABLE_NAME>=<VALUE>.

Variable	Description	Default
`USER_ID`	ID of the user the application runs as. See User/Group IDs to better understand when this should be set.	`1000`
`GROUP_ID`	ID of the group the application runs as. See User/Group IDs to better understand when this should be set.	`1000`
`SUP_GROUP_IDS`	Comma-separated list of supplementary group IDs of the application.	(unset)
`UMASK`	Mask that controls how file permissions are set for newly created files. The value of the mask is in octal notation. By default, this variable is not set and the default umask of `022` is used, meaning that newly created files are readable by everyone, but only writable by the owner. See the following online umask calculator: http://wintelguy.com/umask-calc.pl	(unset)
`TZ`	TimeZone of the container. Timezone can also be set by mapping `/etc/localtime` between the host and the container.	`Etc/UTC`
`KEEP_APP_RUNNING`	When set to `1`, the application will be automatically restarted if it crashes or if a user quits it.	`0`
`APP_NICENESS`	Priority at which the application should run. A niceness value of -20 is the highest priority and 19 is the lowest priority. By default, niceness is not set, meaning that the default niceness of 0 is used. NOTE: A negative niceness (priority increase) requires additional permissions. In this case, the container should be run with the docker option `--cap-add=SYS_NICE`.	(unset)
`CLEAN_TMP_DIR`	When set to `1`, all files in the `/tmp` directory are deleted during the container startup.	`1`
`DISPLAY_WIDTH`	Width (in pixels) of the application's window.	`1280`
`DISPLAY_HEIGHT`	Height (in pixels) of the application's window.	`768`
`SECURE_CONNECTION`	When set to `1`, an encrypted connection is used to access the application's GUI (either via a web browser or VNC client). See the Security section for more details.	`0`
`VNC_PASSWORD`	Password needed to connect to the application's GUI. See the VNC Password section for more details.	(unset)
`X11VNC_EXTRA_OPTS`	Extra options to pass to the x11vnc server running in the Docker container. WARNING: For advanced users. Do not use unless you know what you are doing.	(unset)
`ENABLE_CJK_FONT`	When set to `1`, open-source computer font `WenQuanYi Zen Hei` is installed. This font contains a large range of Chinese/Japanese/Korean characters.	`0`

Data Volumes

The following table describes data volumes used by the container. The mappings are set via the -v parameter. Each mapping is specified with the following format: <HOST_DIR>:<CONTAINER_DIR>[:PERMISSIONS].

Container path	Permissions	Description
`/config`	rw	This is where the application stores its configuration, log and any files needing persistency.

Ports

Here is the list of ports used by the container. They can be mapped to the host via the -p parameter (one per port mapping). Each mapping is defined in the following format: <HOST_PORT>:<CONTAINER_PORT>. The port number inside the container cannot be changed, but you are free to use any port on the host side.

Port	Mapping to host	Description
5800	Mandatory	Port used to access the application's GUI via the web interface.
5900	Optional	Port used to access the application's GUI via the VNC protocol. Optional if no VNC client is used.

Changing Parameters of a Running Container

As seen, environment variables, volume mappings and port mappings are specified while creating the container.

The following steps describe the method used to add, remove or update parameter(s) of an existing container. The generic idea is to destroy and re-create the container:

Stop the container (if it is running):

docker stop firefox

Remove the container:

docker rm firefox

Create/start the container using the docker run command, by adjusting parameters as needed.

NOTE: Since all application's data is saved under the /config container folder, destroying and re-creating a container is not a problem: nothing is lost and the application comes back with the same state (as long as the mapping of the /config folder remains the same).

Docker Compose File

Here is an example of a docker-compose.yml file that can be used with Docker Compose.

Make sure to adjust according to your needs. Note that only mandatory network ports are part of the example.

version: '3'
services:
  firefox:
    image: jlesage/firefox
    build: .
    ports:
      - "5800:5800"
    volumes:
      - "/docker/appdata/firefox:/config:rw"

Docker Image Update

If the system on which the container runs doesn't provide a way to easily update the Docker image, the following steps can be followed:

Fetch the latest image:

docker pull jlesage/firefox

Stop the container:

docker stop firefox

Remove the container:

docker rm firefox

Start the container using the docker run command.

Synology

For owners of a Synology NAS, the following steps can be used to update a container image.

Open the Docker application.
Click on Registry in the left pane.
In the search bar, type the name of the container (jlesage/firefox).
Select the image, click Download and then choose the latest tag.
Wait for the download to complete. A notification will appear once done.
Click on Container in the left pane.
Select your Firefox container.
Stop it by clicking Action->Stop.
Clear the container by clicking Action->Clear. This removes the container while keeping its configuration.
Start the container again by clicking Action->Start. NOTE: The container may temporarily disappear from the list while it is re-created.

unRAID

For unRAID, a container image can be updated by following these steps:

Select the Docker tab.
Click the Check for Updates button at the bottom of the page.
Click the update ready link of the container to be updated.

User/Group IDs

When using data volumes (-v flags), permissions issues can occur between the host and the container. For example, the user within the container may not exists on the host. This could prevent the host from properly accessing files and folders on the shared volume.

To avoid any problem, you can specify the user the application should run as.

This is done by passing the user ID and group ID to the container via the USER_ID and GROUP_ID environment variables.

To find the right IDs to use, issue the following command on the host, with the user owning the data volume on the host:

id <username>

Which gives an output like this one:

uid=1000(myuser) gid=1000(myuser) groups=1000(myuser),4(adm),24(cdrom),27(sudo),46(plugdev),113(lpadmin)

The value of uid (user ID) and gid (group ID) are the ones that you should be given the container.

Accessing the GUI

Assuming that container's ports are mapped to the same host's ports, the graphical interface of the application can be accessed via:

A web browser:

http://<HOST IP ADDR>:5800

Any VNC client:

<HOST IP ADDR>:5900

Security

By default, access to the application's GUI is done over an unencrypted connection (HTTP or VNC).

Secure connection can be enabled via the SECURE_CONNECTION environment variable. See the Environment Variables section for more details on how to set an environment variable.

When enabled, application's GUI is performed over an HTTPs connection when accessed with a browser. All HTTP accesses are automatically redirected to HTTPs.

When using a VNC client, the VNC connection is performed over SSL. Note that few VNC clients support this method. SSVNC is one of them.

SSVNC

SSVNC is a VNC viewer that adds encryption security to VNC connections.

While the Linux version of SSVNC works well, the Windows version has some issues. At the time of writing, the latest version 1.0.30 is not functional, as a connection fails with the following error:

ReadExact: Socket error while reading

However, for your convenience, an unofficial and working version is provided here:

https://github.com/jlesage/docker-baseimage-gui/raw/master/tools/ssvnc_windows_only-1.0.30-r1.zip

The only difference with the official package is that the bundled version of stunnel has been upgraded to version 5.49, which fixes the connection problems.

Certificates

Here are the certificate files needed by the container. By default, when they are missing, self-signed certificates are generated and used. All files have PEM encoded, x509 certificates.

Container Path	Purpose	Content
`/config/certs/vnc-server.pem`	VNC connection encryption.	VNC server's private key and certificate, bundled with any root and intermediate certificates.
`/config/certs/web-privkey.pem`	HTTPs connection encryption.	Web server's private key.
`/config/certs/web-fullchain.pem`	HTTPs connection encryption.	Web server's certificate, bundled with any root and intermediate certificates.

NOTE: To prevent any certificate validity warnings/errors from the browser or VNC client, make sure to supply your own valid certificates.

NOTE: Certificate files are monitored and relevant daemons are automatically restarted when changes are detected.

VNC Password

To restrict access to your application, a password can be specified. This can be done via two methods:

By using the VNC_PASSWORD environment variable.
By creating a .vncpass_clear file at the root of the /config volume. This file should contain the password in clear-text. During the container startup, content of the file is obfuscated and moved to .vncpass.

The level of security provided by the VNC password depends on two things:

The type of communication channel (encrypted/unencrypted).
How secure the access to the host is.

When using a VNC password, it is highly desirable to enable the secure connection to prevent sending the password in clear over an unencrypted channel.

ATTENTION: Password is limited to 8 characters. This limitation comes from the Remote Framebuffer Protocol RFC (see section 7.2.2). Any characters beyond the limit are ignored.

Reverse Proxy

The following sections contain NGINX configurations that need to be added in order to reverse proxy to this container.

A reverse proxy server can route HTTP requests based on the hostname or the URL path.

Routing Based on Hostname

In this scenario, each hostname is routed to a different application/container.

For example, let's say the reverse proxy server is running on the same machine as this container. The server would proxy all HTTP requests sent to firefox.domain.tld to the container at 127.0.0.1:5800.

Here are the relevant configuration elements that would be added to the NGINX configuration:

map $http_upgrade $connection_upgrade {
	default upgrade;
	''      close;
}

upstream docker-firefox {
	# If the reverse proxy server is not running on the same machine as the
	# Docker container, use the IP of the Docker host here.
	# Make sure to adjust the port according to how port 5800 of the
	# container has been mapped on the host.
	server 127.0.0.1:5800;
}

server {
	[...]

	server_name firefox.domain.tld;

	location / {
	        proxy_pass http://docker-firefox;
	}

	location /websockify {
		proxy_pass http://docker-firefox;
		proxy_http_version 1.1;
		proxy_set_header Upgrade $http_upgrade;
		proxy_set_header Connection $connection_upgrade;
		proxy_read_timeout 86400;
	}
}

Routing Based on URL Path

In this scenario, the hostname is the same, but different URL paths are used to route to different applications/containers.

For example, let's say the reverse proxy server is running on the same machine as this container. The server would proxy all HTTP requests for server.domain.tld/firefox to the container at 127.0.0.1:5800.

Here are the relevant configuration elements that would be added to the NGINX configuration:

map $http_upgrade $connection_upgrade {
	default upgrade;
	''      close;
}

upstream docker-firefox {
	# If the reverse proxy server is not running on the same machine as the
	# Docker container, use the IP of the Docker host here.
	# Make sure to adjust the port according to how port 5800 of the
	# container has been mapped on the host.
	server 127.0.0.1:5800;
}

server {
	[...]

	location = /firefox {return 301 $scheme://$http_host/firefox/;}
	location /firefox/ {
		proxy_pass http://docker-firefox/;
		location /firefox/websockify {
			proxy_pass http://docker-firefox/websockify/;
			proxy_http_version 1.1;
			proxy_set_header Upgrade $http_upgrade;
			proxy_set_header Connection $connection_upgrade;
			proxy_read_timeout 86400;
		}
	}
}

Shell Access

To get shell access to a the running container, execute the following command:

docker exec -ti CONTAINER sh

Where CONTAINER is the ID or the name of the container used during its creation (e.g. crashplan-pro).

Increasing Shared Memory Size

To prevent crashes from happening when running Firefox inside a Docker container, the size of the shared memory located at /dev/shm must be increased. The issue is documented here.

By default, the size is 64MB, which is not enough. It is recommended to use a size of 2GB. This value is arbitrary, but known to work well. Setting the size of /dev/shm can be done via two method:

By adding the --shm-size 2g parameter to the docker run command. See the Usage section for more details.
By using shared memory of the host, by mapping /dev/shm via the parameter -v /dev/shm:/dev/shm of the docker run command.

Allowing the membarrier System Call

To properly work, recent versions of Firefox need the membarrier system call. Without it, tabs would frequently crash.

Docker uses seccomp profile to restrict system calls available to the container. Before Docker version 20.03.0, the membarrier system call was not allowed in the default profile. If you run a such version, you can use one of the following solutions, from the most to the least secure, to provide the container permission to use this sytem call:

Run the container with a custom seccomp profile allowing the membarrier system call. The latest official seccomp profile can be used. Download the file and then add the following parameter when creating the container: --security-opt seccomp=/path/to/seccomp_profile.json.
Run the container without the default seccomp profile (thus allowing all system calls). Use the following parameter when creating the container: --security-opt seccomp=unconfined.
Run the container in privileged mode. This effectively disables usage of seccomp. Add the --privileged parameter when creating the container.

Sound Support

For Firefox to be able to use the audio device available on the host, /dev/snd must be exposed to the container by adding the --device /dev/snd parameter to the docker run command.

Setting Firefox Preferences Via Environment Variables

Firefox preferences can be set via environment variables passed to the container. During the startup, a script process all these variables and modify the preference file accordingly.

The name of the environment variable must start with FF_PREF_, followed by a string of your choice. For example, FF_PREF_MY_PREF is a valid name.

The content of the variable should be in the format NAME=VAL, where NAME is the name of the preference (as found in the about:config page) and VAL is its value. A value can be one of the following types:

string
integer
boolean

It is important to note that a value of type string should be surrounded by double quotes. Other types don't need them.

For example, to set the network.proxy.http preference, one would pass the environment variable to the container by adding the following argument to the docker run command:

-e "FF_PREF_HTTP_PROXY=network.proxy.http=\"proxy.example.com\""

If a preference needs to be removed, its value should be set to UNSET. For example:

-e "FF_PREF_HTTP_PROXY=network.proxy.http=UNSET"

NOTE: This is an advanced usage and it is recommended to set preferences via Firefox directly.

Troubleshooting

Crashes

If Firefox is crashing frequently, make sure that:

The size of the shared memory located at /dev/shm has been increased. See the Increasing Shared Memory Size section for more details.
The membarrier system call is not blocked by Docker. See the Allowing the membarrier System Call for more details.

Support or Contact

Having troubles with the container or have questions? Please create a new issue.

For other great Dockerized applications, see https://jlesage.github.io/docker-apps.

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README.md

README.md

Docker container for Firefox

Table of Content

Quick Start

Usage

Environment Variables

Data Volumes

Ports

Changing Parameters of a Running Container

Docker Compose File

Docker Image Update

Synology

unRAID

User/Group IDs

Accessing the GUI

Security

SSVNC

Certificates

VNC Password

Reverse Proxy

Routing Based on Hostname

Routing Based on URL Path

Shell Access

Increasing Shared Memory Size

Allowing the membarrier System Call

Sound Support

Setting Firefox Preferences Via Environment Variables

Troubleshooting

Crashes

Support or Contact

Files

README.md

Latest commit

History

README.md

File metadata and controls

Docker container for Firefox

Table of Content

Quick Start

Usage

Environment Variables

Data Volumes

Ports

Changing Parameters of a Running Container

Docker Compose File

Docker Image Update

Synology

unRAID

User/Group IDs

Accessing the GUI

Security

SSVNC

Certificates

VNC Password

Reverse Proxy

Routing Based on Hostname

Routing Based on URL Path

Shell Access

Increasing Shared Memory Size

Allowing the membarrier System Call

Sound Support

Setting Firefox Preferences Via Environment Variables

Troubleshooting

Crashes

Support or Contact