Any way to prevent local compilation?

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1

Lately started to get haunted by hydra failures. (Relevant thread)

Today my laptop was levitating again due to fans. It was again thunderbird.

Is there a way to prevent local build? At least for certain packages? I realize that’s an odd question, but I’d rather see a nixos-rebuild to fail then compiling some of the apps I have.

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2

Maybe try --max-jobs 0 with a remote builder.

3

Another possibility is using nixus or deploy-rs from another computer and deploy the result to your laptop. Here’s my config GitHub - bbigras/nix-config: My personal nix config . 3 days a week a github action updates my packages with niv, builds the config for multiple computers and pushes it to cachix so I don’t have to build anything on my computers.

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Is it possible to specify max-jobs in conjunction with autoUpgrade though?

5

I’m not 100% sure but I think so. You can set nix.maxJobs = 0; in configuration.nix.

I used it before to avoid using too many resources on an important system.

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:warning I tried this now and it turned out to be a very bad idea. Once you switched to that and nix-channel --updated, you cannot go back that easily, because it also prevents you from building a configuration without nixos.maxJobs = 0 (obviously).

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7

You can just run nixos-rebuild boot -j 1 or any similar nix-build command with the -j X option to allow local builds again.

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8

Unfortunately -j X doesn’t seem to be combinable with --upgrade:

# nixos-rebuild boot -j 1 --upgrade
unpacking channels...
error: 1 derivations need to be built, but neither local builds ('--max-jobs') nor remote builds ('--builders') are enabled
error: program '/nix/store/agzmb1cin5dn8wlbfmkbbjzvz4422yys-nix-2.3.9/bin/nix-env' failed with exit code 1
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Works for me:

# nixos-rebuild boot --upgrade -j1 --builders ''
unpacking channels...
created 1 symlinks in user environment
building Nix...
building the system configuration...
these derivations will be built:
  /nix/store/j3ccp5lyzbcw9aziqjs6kc589y218l3r-nixos-version.drv
  /nix/store/rd8fxmag28ybiqwbmk17l9ads057z8jx-system-path.drv
  /nix/store/ly9r5vhly6xiww36yy16gxrkkgvkq658-dbus-1.drv

Maybe the order of the arguments matter, I’m not sure about that.