Kernel downgrade after channel update

Hello All,

i have a laptop which is running on the “nixos-20.03” beta channel. After i updated this single channel on the system with “sudo nix-channel --update nixos” and rebuilt the system with “sudo nixos-rebuild boot”, it appears the system has downgraded some packages, notably the linux kernel from 5.4.23 to 5.4.21. See attached picture. How is this possible?

While not exactly sure what happened, it would appear that i have to do a lot more reading about the process of how the channels are updated, i.e. about commits to the channel branches on github, about hydra and the channel update process.

I’m still playing around a lot with nixos and this must have been a leftover from a imported/removed kernel from a unstable channel.

Sorry for the noise.

What i dont understand: As a example, says the nixos-20.03 channel has now been updated 15 Hours ago, but the referenced commit refers to a commit to the channel branch on github made 12 days ago. Does this mean the channel’s hydra builds have been failing the jobset evaluations jobs for the last 12 days for the channel to update?

The commit dates are when the person did git commit ... , seeing as you’re inspecting on a release channel. Those need go into master (if applicable), then get backported (doesn’t change commit date) to the respective channel. Which takes a while, and will likely be “out-of-order”.

This mirror should be a better source of truth:

I’m assuming you have more than one channel, do nix-channel --list and sudo nix-channel --list

Ah, OK… nixpkgs ≠ nixpkgs-channels.

As i understand from the section “How does channel update?” from, conditions for the build have to be met to trigger a channel update.

Are these builds done on a daily basis or when or what does trigger these?

sudo nix-channel --list
[sudo] password for sydney:

I have no channels in my user environment, or not anymore.

I guess, i just got confused by different nix configurations on different machines.

I have this in my config, but cannot remember, or lost track about wether or not it was commented out.

nixpkgs.config = {
  packageOverrides = pkgs: {
    unstable = import <unstable> {
      config = config.nixpkgs.config;

#boot.kernelPackages = with pkgs; unstable.linuxPackages_latest ;

Then again, this is by far no production issue or even a nix issue, more a issue of me losing track while toying around and a lack of understand about nix packaging. In hindsight, i also have chosen a poorly title for this thread.