Docker container for Chromium

This is a Docker container for Chromium.

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

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Big thanks to @jlesage. This image is based off https://github.com/jlesage/docker-firefox

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Table of Content

• Docker container for Chromium
  • 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
  • Sound Support
  • Setting Chromium Preferences Via Environment Variables
  • Troubleshooting
    • Crashes
  • Support or Contact

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 Chromium docker container with the following command:

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

Where:

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

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

Usage

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

Parameter	Description
-d	Run the container in background. If not set, the container runs in 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 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 delete 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 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:

1. Stop the container (if it is running):

docker stop chromium

2. Remove the container:

docker rm chromium

3. 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:
  chromium:
    image: overclockedllama/docker-chromium
    build: .
    ports:
      - "5800:5800"
    volumes:
      - "/docker/appdata/chromium:/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:

1. Fetch the latest image:

docker pull overclockedllama/docker-chromium

2. Stop the container:

docker stop chromium

3. Remove the container:

docker rm chromium

4. Start the container using the docker run command.

Synology

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

1. Open the Docker application.
2. Click on Registry in the left pane.
3. In the search bar, type the name of the container (overclockedllama/docker-chromium).
4. Select the image, click Download and then choose the latest tag.
5. Wait for the download to complete. A notification will appear once done.
6. Click on Container in the left pane.
7. Select your Chromium container.
8. Stop it by clicking Action->Stop.
9. Clear the container by clicking Action->Clear. This removes the container while keeping its configuration.
10. 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:

1. Select the Docker tab.
2. Click the Check for Updates button at the bottom of the page.
3. 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 convienence, an unoffical 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 offical 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 contains 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 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 beyhond the limit are ignored.

Reverse Proxy

The following sections contains NGINX configuration 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 chromium.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-chromium {
	# 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 chromium.domain.tld;

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

	location /websockify {
		proxy_pass http://docker-chromium;
		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/chromium 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-chromium {
	# 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 = /chromium {return 301 $scheme://$http_host/chromium/;}
	location /chromium/ {
		proxy_pass http://docker-chromium/;
		location /chromium/websockify {
			proxy_pass http://docker-chromium/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 -it 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 Chromium 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.

Sound Support

For Chromium 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.

Troubleshooting

Crashes

If Chromium is crashing frequently, make sure the size of the shared memory located at /dev/shm has been increased. See Increasing Shared Memory Size section 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.