System-manager and nix store size

bza · August 2, 2026, 3:29pm

Hi,

just trying system-manager for the 1st time. The system I’m using it on does not have too much disk space available. I wonder

how one would clean the nix store managed by system-manager, and
if it would help to build on another machine?

Thanks!

bza · August 2, 2026, 3:31pm

Summoning @zimbatm or @Mic92 - hope you don’t mind

NobbZ · August 2, 2026, 3:59pm

Do garbage collections and keep the system closures small. Whether you use System-Manager, home-manager, nixOS, or just plain nix doesn’t really change anything about this.

Understand what nix considers garbage and what it doesn’t, and make sure that nix has roughly the same understanding as you.

bza · August 2, 2026, 5:38pm

Ah ok, thank you.

I think in the past I already had a way to list GC roots, etc. on nixos.

So I think I will just try the usual GC commands and see, b/c I had to stop some larger installation. I should see some space being freed up.

bitbloxhub · August 2, 2026, 7:44pm

I use @linyinfeng’s angrr to automatically clean up gcroots. Example system-manager config:

github.com/bitbloxhub/nixos-config

nix/angrr.nix

df865c194


      
          systemManager =
            {
              pkgs,
              inputs',
              ...
            }:
            {
              environment = {
                etc."angrr/config.toml".source = (pkgs.formats.toml { }).generate "angrr/config.toml" angrrConfig;
                systemPackages = [ inputs'.angrr.packages.default ];
              };
              systemd = {
                services.angrr = {
                  description = "Auto Nix GC Roots Retention";
                  environment.ANGRR_LOG_STYLE = "systemd";
                  script = ''
                    ${lib.getExe inputs'.angrr.packages.default} run \
                      --log-level "info" \
                      --no-prompt
                  '';

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bza · August 2, 2026, 9:14pm

Thank you very much. Will check.

bza · August 4, 2026, 10:27am

Just to close this up. I now have an angrr service similar to yours. Works, ig.

Added another service calling nix-collect-garbage -d every night.

So, thank you again!