Keeping up with the latest updates in the 19.03 release, we covered a topic called “fast context switching”. A context is the configuration in which we interact with Docker, Swarm, or Kubernetes on a specific server. Context switching allows you to quickly change between multiple Docker endpoints without having to go in and set/unset environment variables.

By saving a remote endpoint as a context, you can quickly shift between talking to multiple different clusters or individual nodes in a single line command. For instance, if you have a test cluster, you can save the remote endpoint in a context called “test” and then run docker -c test ps from your local CLI. This will run the ps command on the test cluster endpoint, bypassing the need to change environment variables, or SSH into the test server. To immediately compare your test cluster with a prod cluster, all you would need to do is create another context for production, and you can switch to the context with the docker context use command, or just switch for a one off command like we did before using the -c option, with docker -c prod <docker command>. Also, these contexts can talk to more than just one type of cluster. In the blog post below, Ajeet has 3 contexts saved of a Swarm cluster, a Kubernetes cluster, and a play-with-docker cluster.

Another really cool feature that was demonstrated by Marcos Nils in my 19.03 release party was that we can save these contexts so that we can interact with a remote endpoint over SSH instead of TCP+TLS. We could run the command docker context create ssh –docker “host=ssh://root@x.x.x.x”, or if you add a friendly name to your server in the “.ssh/config” file, you can substitute the IP for the friendly name there too!

Thanks for reading,

–Bret

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