CentOS 8 Stream on your favorite cloud provider

Q2 is closing in for the first release of Rocky Linux, but until that rolls around I think it might be a good time to give CentOS Stream a try.

While I'm probably one of those users who will jump ship once Rocky Linux hits the shelves, so to speak, 2021 might not necessarily be the moment I make the switch. I'm not going to rant about RedHat's current track record; I will say that I somehow managed to trip on a couple of differences between RedHat 8 and CentOS 8. Which should even exist in the first place. Hopefully, the same issues aren't going to resurface with Rocky Linux. With the amount of Ansible roles I depend on daily, I'll wait things out a bit to stabilize first.

Anyway. If you like to give Stream a try, AWS at least has official images ready to go. But if you're on a different cloud provider that doesn't, no need to worry. As long as they provide CentOS 8 and have cloud-init support (which cloud provider doesn't nowadays?) you can use the following cloud-init file to switch from CentOS 8 to Stream.

#cloud-config
runcmd:
  - dnf install --assumeyes centos-release-stream
  - dnf swap --assumeyes centos-{linux,stream}-repos
  - dnf --assumeyes distro-sync
  - reboot
output : { all : '| tee -a /var/log/cloud-init-output.log' }

If you're not familiar with cloud-init, you dump these lines in the cloud-init/user data field that your cloud provider exposes. Then, on the first machine boot up, cloud-init will run the set of tasks, and only after will the machine be marked as ready. You can refer to their documentation. It is quite an extensive configuration format.

Do note that the #cloud-config comment is essential. It defines the format of the lines to follow (can swap it with a shebang if you want to write a shell script directly).

Additionally, after the reboot, you will want to run a package update. Initially, I had the update in my set of commands, but DigitalOcean would cut the execution of dnf update, based on some opaque timeout criteria (?!).

Some providers might already create the /var/log/cloud-init-output.log by default, but better to be explicit. If a cat /etc/*release within the machine still shows CentOS 8 as the release name, refer back to this log file for any runtime issues.

mhitza/centos-stream.md