Lightning-fast CI with

You can now run builds on like this:

nix build --eval-store auto --store ssh-ng:// ...

This “remote store” usage means that the build will performed entirely on the remote side ( in this case), with no build inputs or build outputs fetched to the local store. For some setups (like CI environments with “empty” runners, like GitHub Actions) this can avoid a whole lot of closure copying, improving build times for certain builds tremendously.

Check out my blog post if this sounds interesting: Lightning-fast CI with


How does this work in presence of IFD?

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It works fine! Here I’m building the IFD example from the NixOS wiki:

$ nix build ".#test-builds/ifd" \
    -v \
    --option allow-import-from-derivation true \
    --eval-store auto \
    --store ssh-ng://

building '/nix/store/602cybzp7c8349dk10rkkvsavh6idhm1-example.drv'...
copying 1 paths...
copying path '/nix/store/iqwcnnvkpsldjrb3v1gxl9yml6yj7131-hello-2.10-ifd-example.94235f45.drv' to 'ssh-ng://'...
building '/nix/store/iqwcnnvkpsldjrb3v1gxl9yml6yj7131-hello-2.10-ifd-example.94235f45.drv'...

As you can see, the generated derivation is built and evaluated locally first, then the resulting .drv is uploaded to and built there.

If your generated derivation needs a lot of build inputs I guess it will defeat some of the purpose of remote store building, since Nix then will need to fetch those closures locally. I think that Nix can run the actual builds of the generated derivations on, but then you need to specify --builders (or configure /etc/nix/machines) in addition to the store options. I have not tested this.

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