How to use Docker with Synology

Synology DSM 6.0 or higher comes with the Docker Engine. You can find the Docker App in the package center by entering docker in the search field.

Docker is a lean virtualization application platform, thousands of containers created by developers from all over the world can be executed and are published on the well-known image repository, called Docker Hub. Container images can be find on Docker Hub will loaded and executed from Synology’s integrated Docker App.

If the Docker App does not appear in the Package Center, the Synology device is most likely not supported.

Due to the hardware requirements, Docker is only offered for models with virtualization technology (VT-x). The models used in this guide are RS820RP+ / RS4018xs+ / DS218+ for these the Docker ability is given.

How to use Docker

When you open the main menu icon from DSM, you will find the icon for the Docker Engine, which can now be started.

Docker opens in overview, the running containers are listed here, any applications including allocated memory and CPU resources, number of container has yet been started.

In addition, the Docker command line is explained below, this as a alternative hint for using Docker Console.

CLI Docker Command Running Container:

docker ps

In the Registration section you can search for new images (like on the official website). New repositories (in addition to the official ones) can also be added under Settings.

CLI the original Docker Command is:

docker search ubuntu-sshd

After a suitable image has been found, in this case a small Ubuntu 18.04 Dockerized image contains SSH service, it is downloaded with a right click on the Synology NAS, ideally always choosing latest. All images are write-protected and can be used multiple times for other containers.

The download can take a few minutes, depending on the size and available download bandwidth. The download status is shown with an animated icon.

CLI Docker Command is:

docker pull rastasheep/ubuntu-sshd

The downloaded images that are available on the Synology NAS are located under Image. New containers can be started with the Docker wizard. Note link symbol opens the Docker Hub page for container with useful information.

CLI Docker Command is:

docker images -a

Now go to Start will open the Assistent.

Next to complete the wizard and start the container with klick Apply.

CLI Docker Command is:

docker run -d -P --name ubuntu rastasheep/ubuntu-sshd

Running container can now be found in the Container section.

CLI Docker full output as follows:

~# docker pull rastasheep/ubuntu-sshd
Using default tag: latest
latest: Pulling from rastasheep/ubuntu-sshd
a48c500ed24e: Pull complete
Digest: sha256:1a4010f95f6b3292f95fb26e442f85885d523f9a0bb82027b718df62fdd0d9e9
Status: Downloaded newer image for rastasheep/ubuntu-sshd:latest
~# docker run -d -P --name ubuntu rastasheep/ubuntu-sshd
2f96bba413755a843c2758f818dbec56f0e163a232e1cb7c7c971034c62a8c98

Back to Docker overview, we can now see the resources of started containers.

CLI Docker Command is:

docker ps -a

Now we are trying to establish an SSH terminal to the container. To do this in the Container section, click on Details to see which port the SSH service is listening on.

In the overview under port settings we find the value we are looking for under local port, in this case it is port 32789, the port address is assigned automatically.

CLI  Determine port address.

~# docker port ubuntu 22
0.0.0.0:32789

Now we open PuTTY or KiTTY and connect to IP of the Synology NAS with port 32789 to the container, for CLI Command as follows:

~# ssh -p 32789 root@10.127.52.77
The authenticity of host '[10.127.52.77]:32789 ([10.127.52.77]:32789)' can't be established.
ECDSA key fingerprint is SHA256:YtTfuoRRR4qStSVA5UuxnGamA/dvf+djbIT2Y48IYD0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[10.127.52.77]:32789' (ECDSA) to the list of known hosts.
root@10.127.52.77's password:
Last login: Thu Sep 19 15:00:25 2018 from 172.18.0.1
root@rastasheep-ubuntu-sshd1:~#

Logon as root with the password of root.

The Docker Engine can also be used from the console, provided the SSH terminal that has been activated under DSM Control Panel – SSH Service.

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

The Docker application shown in this article is intended to show as a simple example how Docker can be used on a Synology NAS, of course there are more useful container applications, such as Websever for developing web applications to complete development environments, there are already countless Docker images on Docker Hub https://hub.docker.com, and other Docker registrars. It makes you wonder whether the effort to install your development environment such as Xamp or LAMP is still useful. At this point it should be mentioned that all data stored in the container must be saved on a persistent volume, because all work is lost when the container is closed.

There are also other articles about using Docker here in this blog, the best thing to do is to simply enter docker in the search field above.