Control remote containers with Docker contexts over SSH

When working with remote servers, SSH is the go-to protocol. But constantly connecting to machines to run Docker commands there gets tedious. Docker contexts let you switch between local and remote Docker daemons seamlessly.

Here’s how to set up a Docker context over SSH and run a simple container remotely.

Prerequisites

Ensure you can SSH into the remote host without a password using SSH keys. You also need Docker installed locally and on the remote server.

Create a new Docker context using SSH

First, we're creating a Docker context with SSH. Replace

docker context create <context-name> \
  --docker "host=ssh://<user>@<your.remote.host>"

Use your new context

There are different ways to use a context. One is to activate the remote context until you switch it again:

docker context use <context-name>
docker context ls

Another common way is to use it in every command explicitly. This is more flexible, but every command needs to carry the context parameter:

docker --context <context-name> context ls

Execute Docker commands on the remote host

For the rest of this article we're going with the activated context. Let's see, what Docker containers are running:

docker context use <context-name>
docker ps

Or let's start a vanilla NGINX server:

docker run \
  --rm --detach \
  --name nginx-test \
  --publish 8080:80 \
  nginx

The container is now running on the remote server, accessible via http://<your.remote.host>:8080.

You can issue every command as you would with a local container. Often you need to open a shell inside the container:

docker exec --tty --interactive nginx-test bash

Try ls or env to verify. That's all for now, so exit the interactive shell with CTRL+D and stop the container. It gets automatically removed, because of the --rm flag we used in the run command above:

docker stop nginx-test

Don't forget to switch back to your local Docker context with docker context use default.

Summary

Docker contexts are a clean way to manage multiple environments, especially remote ones. Once set up, it's as easy as flipping a switch. They can also be shared with others using the docker context export and docker context import commands.

In practice, I’ve used this for:

• Managing test and production environments on remote hosts
• Debugging production issues
• Automating remote builds and deployments

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