This is the first of a series of posts about random things that I get to learn. This one, the first, is a short story about those things you form an idea around swearing that it’s true until it’s not.

What did I learn today?

That Compose is an open specification from the CNCF (Cloud Native Computing Foundation). I always thought that it was Docker’s ‘proprietary’ format to define resources in a containerized environment á-la-kubernetes.

They (Docker) partnered with other players to make it an open format in 2020. I guess that it’s never too late to get the news?

Hosting services

I have an ‘old’ desktop computer that I use as my main server in my homelab. I host some of my services there by exposing containers with persistent volumes. Most of them are defined with the Compose specification, managed with docker on Linux. I try to keep everything up to date as early as it’s released, but it was a long time ago since I upgraded any of the versions of my services.

This weekend, while at it, I started getting a warning:

WARN[0000] /myroute/to/service/docker-compose.yml: version is obsolete

And the version I had in all the compose files is was 3.8.

“The fix”

A simple one: removing the version line from the compose file, as this one is already deprecated.

What does that version number mean?

According to the docs, these versions (2.x and 3.x) accounted for features introduced during the development of the specification (such as Docker Swarm features in 3.x), and it basically identifies the file format and its elements. The new Compose specification doesn’t seems to keep track of these changes with a version number.