The LinuxServer.io team brings you another container release featuring:

• regular and timely application updates
• easy user mappings (PGID, PUID)
• custom base image with s6 overlay
• weekly base OS updates with common layers across the entire LinuxServer.io ecosystem to minimise space usage, down time and bandwidth
• regular security updates

Find us at:

• Blog - all the things you can do with our containers including How-To guides, opinions and much more!
• Discord - realtime support / chat with the community and the team.
• Discourse - post on our community forum.
• GitHub - view the source for all of our repositories.
• Open Collective - please consider helping us by either donating or contributing to our budget

Sealskin is a self-hosted, client-server platform that enables users to run powerful, containerized desktop applications streamed directly to a web browser. It uses a browser extension to intercept user actions—such as clicking a link or downloading a file and redirects them to a secure, isolated application environment running on a remote server.

We utilise the docker manifest for multi-platform awareness. More information is available from docker here and our announcement here.

Simply pulling lscr.io/linuxserver/sealskin:latest should retrieve the correct image for your arch, but you can also pull specific arch images via tags.

The architectures supported by this image are:

This image hosts the server component for the SealSkin platform.

Download the browser extension from for Chrome HERE, for Firefox HERE.

On first init a file will be created /config/admin.json if you set HOST_URL you can use this file for credentials as is, if you did not you will need to edit it and change the URL/IP set in the file to use it. Once authenticated in the extension you can generate users and new config files to distribute or use.

It is important to use the container name sealskin as this is how the container identifies itself and determines its ports, volumes, and network. The only backend provider to launch containers is Docker. The storage paths are required for key and storage management while their mount paths are adapted from within the container to be run on the host for launched sessions. Everyting in the stack runs as the PUID and PGID down to the container desktop sessions, it is important that the user you use has access to the /config and /storage paths.

Nvidia support only works on 580 and up full proprietary drivers (no MIT/GPL) with nvidia-drm.modeset=1 kernel parameter set. You must ensure the card is initialized before running a container so on headless systems run nvidia-modprobe --modeset from the host even with this kernel parameter set, this only needs to be run once per boot on headless systems.

The server requires several cryptographic keys to function. You can either let the server perform an automatic setup on its first run or manually provide your own keys for more control.

This is the simplest method. On the first launch with an empty /config volume:

1. An init process automatically generates the mandatory server key (server_key.pem) and a self-signed SSL certificate for the proxy (proxy_key.pem, proxy_cert.pem).
2. The application will then detect that no administrator exists, create a default user named admin, and output a configuration file admin.json into the /config/ directory.

Your only action is if the HOST_URL environment variable is not set to replace the HOST_URL string in the file with your IP/URL.

If you wish to use your own administrator key or provide a valid SSL certificate, you can place the necessary files in the /config volume before the first launch.

• To use a custom Admin Key:

  1. Generate your own RSA keypair.
  2. Create a file containing only your public key PEM data at the following location:
     • Path: /path/to/config/.config/sealskin/keys/admins/admin
  3. The server will detect this file and skip the automatic admin creation. You will use your corresponding private key to log in from the extension.

• To use a custom SSL Certificate:

  • Place your SSL private key and certificate file at these locations. This will override the self-signed certificate generated by the init process.
    • Key Path: /path/to/config/ssl/proxy_key.pem
    • Cert Path: /path/to/config/ssl/proxy_cert.pem

• To use a custom Server E2EE Key:

  • Place your RSA private key at this location. This is the core key for the API's end-to-end encryption and validates the server when a user sets the servers public key when configuring the extension.
    • Path: /path/to/config/ssl/server_key.pem
    • Generation Command: openssl genpkey -algorithm RSA -out /path/to/config/ssl/server_key.pem -pkeyopt rsa_keygen_bits:4096
  • To obtain the corresponding public key (which is needed by the browser extension), you can extract it from your private key with this command:
    • Extraction Command: openssl rsa -in server_key.pem -pubout

To help you get started creating a container from this image you can either use docker-compose or the docker cli.

---
services:
  sealskin:
    image: lscr.io/linuxserver/sealskin:latest
    container_name: sealskin
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Etc/UTC
      - HOST_URL=IP|subdomain.doman.com #optional
    volumes:
      - /path/to/sealskin/config:/config
      - /path/to/sealskin/storage:/storage
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - 8443:8443
      - 8000:8000 #optional
    restart: unless-stopped

docker run -d \
  --name=sealskin \
  -e PUID=1000 \
  -e PGID=1000 \
  -e TZ=Etc/UTC \
  -e HOST_URL=IP|subdomain.doman.com `#optional` \
  -p 8443:8443 \
  -p 8000:8000 `#optional` \
  -v /path/to/sealskin/config:/config \
  -v /path/to/sealskin/storage:/storage \
  -v /var/run/docker.sock:/var/run/docker.sock \
  --restart unless-stopped \
  lscr.io/linuxserver/sealskin:latest

Containers are configured using parameters passed at runtime (such as those above). These parameters are separated by a colon and indicate <external>:<internal> respectively. For example, -p 8080:80 would expose port 80 from inside the container to be accessible from the host's IP on port 8080 outside the container.

You can set any environment variable from a file by using a special prepend FILE__.

As an example:

-e FILE__MYVAR=/run/secrets/mysecretvariable

Will set the environment variable MYVAR based on the contents of the /run/secrets/mysecretvariable file.

For all of our images we provide the ability to override the default umask settings for services started within the containers using the optional -e UMASK=022 setting. Keep in mind umask is not chmod it subtracts from permissions based on it's value it does not add. Please read up here before asking for support.

When using volumes (-v flags), permissions issues can arise between the host OS and the container, we avoid this issue by allowing you to specify the user PUID and group PGID.

Ensure any volume directories on the host are owned by the same user you specify and any permissions issues will vanish like magic.

In this instance PUID=1000 and PGID=1000, to find yours use id your_user as below:

id your_user

Example output:

uid=1000(your_user) gid=1000(your_user) groups=1000(your_user)

We publish various Docker Mods to enable additional functionality within the containers. The list of Mods available for this image (if any) as well as universal mods that can be applied to any one of our images can be accessed via the dynamic badges above.

• Shell access whilst the container is running:

  docker exec -it sealskin /bin/bash

• To monitor the logs of the container in realtime:

  docker logs -f sealskin

• Container version number:

  docker inspect -f '{{ index .Config.Labels "build_version" }}' sealskin

• Image version number:

  docker inspect -f '{{ index .Config.Labels "build_version" }}' lscr.io/linuxserver/sealskin:latest

Most of our images are static, versioned, and require an image update and container recreation to update the app inside. With some exceptions (noted in the relevant readme.md), we do not recommend or support updating apps inside the container. Please consult the Application Setup section above to see if it is recommended for the image.

Below are the instructions for updating containers:

• Update images:

  • All images:

    docker-compose pull

  • Single image:

    docker-compose pull sealskin

• Update containers:

  • All containers:

    docker-compose up -d

  • Single container:

    docker-compose up -d sealskin

• You can also remove the old dangling images:

  docker image prune

• Update the image:

  docker pull lscr.io/linuxserver/sealskin:latest

• Stop the running container:

  docker stop sealskin

• Delete the container:

  docker rm sealskin

• Recreate a new container with the same docker run parameters as instructed above (if mapped correctly to a host folder, your /config folder and settings will be preserved)

• You can also remove the old dangling images:

  docker image prune

If you want to make local modifications to these images for development purposes or just to customize the logic:

git clone https://github.com/linuxserver/docker-sealskin.git
cd docker-sealskin
docker build \
  --no-cache \
  --pull \
  -t lscr.io/linuxserver/sealskin:latest .

The ARM variants can be built on x86_64 hardware and vice versa using lscr.io/linuxserver/qemu-static

docker run --rm --privileged lscr.io/linuxserver/qemu-static --reset

Once registered you can define the dockerfile to use with -f Dockerfile.aarch64.

• 17.01.26: - Update docs to remove network and port requirement, add link to Firefox add on.
• 08.01.26: - Improve permission fixing.
• 31.10.25: - Initial Release.