NixOS 26.05 released

I run nixos-unstable and I don't have stability issues from nixpkgs changes. The rollback functionality is really helpful when I make changes which don't work, e.g. when I've tried changing a graphics driver, kernel, etc.

I have run unstable for a long time. I have found that most really bad bugs (the 'system would fail to run'-kind) virtually never occurs, because Hydra runs a lot of tests, including some that spin up a VM with NixOS. If one or more tests for critical parts of the system fails, the channel won't update, so you are not getting those changes.

The most frequent issue I encounter is when I misconfigure something, usually it's resolved by backing out that change in my configuration and rebuilding the system. Very rarely I boot into an older generation and fix it then (most configuration issues are not so bad that you don't get a working terminal).

Sometimes a particular package has a new issue. I then override it in my configuration with a different version or whatever other build flags/postInstall fixes or whatever are needed. This is one of the cool things of Nix/NixOS, you can override arbitrary packages. For instance, when my ThinkPad was new, I needed a different version of libfprintd-tod for the fingerprint reader. I just made an override in an overlay:

https://codeberg.org/danieldk/nix-home/commit/122cd042bfc031fb41cff0092bfbe8bea4ecab1d

Exactly. Though I haven't had too much trouble updating versions. Usually if something goes wrong and I roll back and wait is because I don't have time to look into it. In fact last time I updated systemd was timing out trying to mount something. It booted and worked, but I rolled back anyway because I didn't want to look into it or suffer through long boots. Might not be something that will fix itself though. Some of the problems I run into are just because I run unstable nixpkgs. I agree mostly with adjacent comment that usually unstable is fine.

Essentially yes. I'm actually doing so right now. Two weeks ago, after an upgrade, GDM broke for reasons that are somewhat over my head and my laptop's graphical session wouldn't start on boot. So I rebooted, selected the previous generation and was back to work in a few minutes. The bug had been reported to nixpkgs already and someone has submitted a PR for it, so I just have to wait until it's merged (which I don't expect will take too long) and I can continue upgrading as usual. I should not that this isn't a common occurrence. It's happened to me once in in just about a year of using NixOS Unstable.

Yeah basically. If it is a big issue sometimes I will pull one package from a different version of NixOS (usually a different stable release) but most of the time it isn't much of an issue and is fixed quickly so I just skip updates for a week.

Same! I ended up with a list of some 10-odd things to check out from the release notes :-)