How do I determine which commit a channel references with Nixos?

Question

I'd like to figure out the commit and date that a channel references.

For example how can determine that for the nixos2009 channel below?

sudo nix-channel --list nixos https://nixos.org/channels/nixos-20.09 nixos-2003 https://nixos.org/channels/nixos-20.03 nixos2003 https://nixos.org/channels/nixos-20.03 nixos2009 https://nixos.org/channels/nixos-20.09 unstable https://nixos.org/channels/nixpkgs-unstable

I can see ls /nix/var/nix/profiles/per-user/root/channels-*/manifest.nix shows us the channel generations.. Which the latest channel generation has the following content:

cat /nix/var/nix/profiles/per-user/root/channels-61-link/manifest.nix | nixfmt [ { meta = { }; name = "nixos-20.09.2538.0cfd08f4881"; out = { outPath = "/nix/store/7s917s7ipvq3zmbx5g3kssldwc029r8r-nixos-20.09.2538.0cfd08f4881"; }; outPath = "/nix/store/7s917s7ipvq3zmbx5g3kssldwc029r8r-nixos-20.09.2538.0cfd08f4881"; outputs = [ "out" ]; system = "x86_64-linux"; type = "derivation"; } { meta = { }; name = "nixos-2003-20.03.3324.929768261a3"; out = { outPath = "/nix/store/zajz4gpq506g68w47pnl11k8mhz06jz0-nixos-2003-20.03.3324.929768261a3"; };

Potentially I can get it from the store path above like /nix/store/zajz4gpq506g68w47pnl11k8mhz06jz0-nixos-2003-20.03.3324.929768261a3 - but I'm not sure (and not sure what that "path" is called either).

Seems like an answer for this is documented here: https://discourse.nixos.org/t/how-to-see-what-commit-is-my-channel-on/4818/6?u=chrissound though that is not a programmatic way (which is what I'm looking for).

BrackNelson · Accepted Answer · 2021-03-23 11:34:34Z

You can use nixos-version. Mine gives 20.03pre194293.2436c27541b (Markhor) where the last part is the commit hash. Not sure if it also works on stable, but it should.

tobiasBora · Accepted Answer · 2022-10-24 07:18:44Z

1

For an arbitrary channel I do it this way (replace nixpkgs with your favorite channel):

$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version' "22.11pre405560.2da64a81275"

Note that the git commit is the last number 2da….

edited Oct 24, 2022 at 7:18

answered Oct 18, 2022 at 11:26

tobiasBora

4,7014 gold badges29 silver badges37 bronze badges

Is there a way to get Nix to emit the full commit hash, instead of the prefix? (Not hard to look it up on Github, of course: github.com/NixOS/nixpkgs/search?q=2da64a81275&type=commits)

Matt R
– Matt R

2022-10-24 09:32:06 +00:00
Commented Oct 24, 2022 at 9:32

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Chris Stryczynski · Accepted Answer · 2023-02-10 15:24:14Z

That manifest might be a nice way.

Another (also in the linked forum) is

readlink /nix/var/nix/profiles/per-user/root/channels-1-link

And also, perhaps the easiest one:

cat /nix/var/nix/profiles/per-user/root/channels/*/svn-revision

On newer versions of nix, the full git commit sha will also be in:

/nix/var/nix/profiles/per-user/root/channels/*/.git-revision

Chris Stryczynski · Accepted Answer · 2024-08-10 15:47:44Z

For your 'user' nix channels:

channelName="nixos2311" cat /nix/var/nix/profiles/per-user/$USER/channels/$channelName/.git-revision

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