About five years ago I wrote an entry on what OSes we were using at the time . Five years is both a short time and a long time here , and in that time some things have changed.

Our primary OS is still Ubuntu LTS; it's our default and we use it on almost everything. On the one hand, these days 'almost everything' covers somewhat more ground than it did in 2020, as some machines have moved from OpenBSD to Ubuntu. On the other hand, as time goes by I'm less and less confident that we'll still be using Ubuntu in five years, because I expect Canonical to start making (more) unfortunate and unacceptable changes any day now. Our most likely replacement Linux is Debian.

CentOS is dead here, killed by a combination of our desire to not have two Linux variants to deal with and CentOS Stream . We got rid of the last of our CentOS machines last year. Conveniently, our previous commercial anti-spam system vendor effectively got out of the business so we didn't have to find a new Unix that they supported.

We're still using OpenBSD, but it's increasingly looking like a legacy OS that's going to be replaced by FreeBSD as we rebuild the various machines that currently run OpenBSD. Our primary interests are better firewall performance and painless mirrored root disks , but if we're going to run some FreeBSD machines and it can do everything OpenBSD can, we'd like to run fewer Unixes so we'll probably replace all of the OpenBSD machines with FreeBSD ones over time. This is a shift in progress and we'll see how far it goes, but I don't expect the number of OpenBSD machines we run to go up any more; instead it's a question of how far down the number goes.

(Our opinions about not using Linux for firewalls haven't changed. We like PF, it's just we like FreeBSD as a host for it more than OpenBSD.)

We continue to not use containers so we don't have to think about a separate, minimal Linux for container images.

There are a lot of research groups here and they run a lot of machines, so research group machines are most likely running a wide assortment of Linuxes and Unixes. We know that Ubuntu (both LTS and non-LTS) is reasonably popular among research groups, but I'm sure there are people with other distributions and probably some use of FreeBSD, OpenBSD, and so on. I believe there may be a few people still using Solaris machines.

(My office desktop continues to run Fedora, but I wouldn't run it on any production server due to the frequent distribution version updates. We don't want to be upgrading distribution versions every six months.)

Overall I'd say we've become a bit more of an Ubuntu LTS monoculture than we were before, but it's not a big change, partly because we were already mostly Ubuntu. Given our views on things like firewalls, we're probably never going to be all-Ubuntu or all-Linux.