Explain what "don't know how to build these paths" means and suggest what to do about it

[copumpkin]

I got that message several times (for the first time in my experience) last night and had no clue what to do about it. I found a couple of mailing list posts from two or three years ago of other people asking and it seemed like the consensus was that something was wonky about the binary cache. I turned off binary caches and the message went away.

It seems like even though it's an unlikely issue to encounter, it's worth documenting what to do with it when we do encounter it.

[masaeedu]

I'm getting this as well. How does one disable the binary cache?

[Shados]

@masaeedu Rather than outright disabling the cache, you may just want to try the --fallback flag first, which will have Nix fall back to building the derivation from source if the binary substitution fails for some reason.

[masaeedu]

@Shados Could you give me some intution for what the error actually means? If it says "don't know how to build these paths", why would adding a flag that tells it to build those paths from source help?

EDIT: tried it out, didn't seem to work in my environment. I ended up using --prebuilt-only.

[stale]

I marked this as stale due to inactivity. → More info

[stale]

I closed this issue due to inactivity. → More info

[runeksvendsen]

So... what does it mean?

[jian-lin]

Is there any way to use that wonky binary cache for those paths again?

My binary cache is served with nix-serve if that matters. Restarting nix-serve has no effect.

[tmillr]

I'm running into this as well (even when using a stable branch—not a channel—as the nixpkgs source) using a flake configuration with nix build and darwin-rebuild switch. I don't have any custom settings set in terms of non-default binary caches. It seems to happen randomly and I've found that the short-term remedy is just to redo/repeat the build as it usually succeeds on the 2nd or 3rd try. Perhaps it has to do with a spontaneous/ephemeral network issue?

[yaitskov]

I get this error 100% of time when do following steps during docker build, though nix-store is working inside other identical docker container and on the host computer

RUN attic login local $atticurl $attickey
RUN attic use mycache
RUN nix-build 
RUN attic push mycache $(realink ./result)
RUN nix-store --store $PWD/copy -r $(realink ./result)

[yaitskov]

Workaround is

rm -rf ~/.cache/nix