Complete implementation of paths-from-graph.pl

[nlewo]

To feed a fresh nix-store from a closure, I'm using the script paths-from-graphs.pl to generate a nix database dump file, that is then used by nix-store --load-db.

The script paths-from-graph.pl generate a dummy sha (instead the drv sha that produced the output path). See https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/kernel/paths-from-graph.pl#L73.

This leads to an incorrect db:

 nix-store --verify-path /nix/store/y4ihw837rm0s0ps5f31zi18w7ri1a0y8-glibc-2.25
path ‘/nix/store/y4ihw837rm0s0ps5f31zi18w7ri1a0y8-glibc-2.25’ was modified! expected hash ‘0000000000000000000000000000000000000000000000000000000000000000’, got ‘b37d7cc7722eb858203ec73f142f46b98c0c0a1038853bb0129532a529c28c0f’

I also have some errors when hydra tryies to copy these paths to the binary cache. But I really don't know if it is related to this error:

while copying/substituting output ‘/nix/store/0yyc337sysd114nfqksv95zgmsapk2cn-python2.7-pytest-xdist-1.18.2’ of ‘/nix/store/9awv5fsv63ggzab8n3rmn9xzs1hwq5pv-python2.7-pytest-xdist-1.18.2.drv’: refusing to copy corrupted path ‘/nix/store/y4ihw837rm0s0ps5f31zi18w7ri1a0y8-glibc-2.25’ to binary cache

I use these mecanism to build a Docker image where nix is usable #28561 . I then use hydra in this container.

You can reproduce by checking out the PR and running:

 % nix-build ./ -A dockerTools.examples.nix && docker load -i result && docker run --rm nix nix-store --verify-path /nix/store/y4ihw837rm0s0ps5f31zi18w7ri1a0y8-glibc-2.25
/nix/store/gaxw3wxm6shmjcs5nla9rzkmh1328ifq-docker-image-nix.tar.gz
Loaded image: nix:latest
warning: the group ‘nixbld’ specified in ‘build-users-group’ does not exist
path ‘/nix/store/y4ihw837rm0s0ps5f31zi18w7ri1a0y8-glibc-2.25’ was modified! expected hash ‘0000000000000000000000000000000000000000000000000000000000000000’, got ‘b37d7cc7722eb858203ec73f142f46b98c0c0a1038853bb0129532a529c28c0f’

To be honnest, i'm really confused with the nix store boostraping. I don't know what is the best way to do it, or if it is simple to fix the paths-from-graph.pl scripts, or...

Any ideas?

[edolstra]

See also NixOS/nix#1134 and NixOS/nix@c2b0d87.

[nlewo]

Thanks.