I assume you mean major release upgrade, I haven't gotten that far yet so I view it as a problem to solve once it arises. Obviously it runs in a container, but

I assume you mean major release upgrade, I haven't gotten that far yet so I view it as a problem to solve once it arises. Obviously it runs in a container, but I have to run the pg_upgrade tool before I start the new container image tag. An immutable OS like CoreOS for example isn't much different than a regular distro. You can still do a lot of manual work on it if you want. I try to avoid doing manual work on it because I want to be strict IaC, but I can for example test doing a major release upgrade in staging, manually over SSH, and work out the kinks, before I put it into practice using containers and scripts in production. Though I see very little reason to automate the hell out of a major release upgrade, better do it safely and slowly with SOP's.