[nix-pin-deps] / README.md

nix-pin-deps: GC-anchor a Nix build's dependencies
--------------------------------------------------

When a Nix build fails for lack of disk space and a `nix-collect-garbage`
is needed to make disk space available, `nix-collect-garbage` will
unhelpfully delete the successfully-built dependencies of the derivation
that failed because they are are not yet gc-anchored, because the
build failed.

This tool solves this problem:

  `nix-pin-deps /nix/store/...-foo.drv foo-deps`

will create gc-anchors in foo-deps/ for all of the dependencies of foo.drv
that exist in the nix store, keeping partial build progress safe from
`nix-collect-garbage`.