[ymse]

Regarding disappearing sources: Nix offers a content-addressed mirror for sources downloaded by the Hydra CI system. As a random example, here is the latest Chromium source tarball:

http://tarballs.nixos.org/sha256/3dfa02e873ff51a11ee02b9ca39...

So disappearing sources is not a huge problem in my experience. Obviously if you have package declarations outside of Nixpkgs proper things are different.

This problem is also something the Software Heritage project[0] aims to solve, but I don't think they have a good API yet.

[0] https://www.softwareheritage.org/

[vishvananda]

Yeah I'm aware of the build mirror, but crashcart builds things under a different prefix so it must build things from source each time. I realize this doesn't affect most users (which is why it takes a while for disappearing sources to be found and fixed). A content addressed mirror for sources as well would solve the problem nicely.

[ymse]

I'm sorry, the mirror is actually for sources, not build artifacts. I've updated my comment to clarify.

[Filligree]

When was that added? Well fetchurl automatically poke it if it can't find the sources otherwise?

[ymse]

Yes, fetchurl will try it:

https://github.com/NixOS/nixpkgs/blob/733151b7825ee8840f7437...

Edit: It was apparently added in 2007:

https://nixos.org/releases/nixpkgs/nixpkgs-0.11/release-note...

[vishvananda]

interesting I wasn't aware of that. I wonder why my builds are not using it.

[catern]

It might be related to using a different Nix prefix for your builds, which is a little poorly supported. Just curious: Why are you using a different prefix?

[vishvananda]

The point of crashcart is to be able to side load a filesystem with utilities into a running container. It is very important that the location we pick doesn't conflict with any path already in the container. If we used /nix as the mount path it would conflict with any container that uses nix. In order to prevent this (probably rare) conflict, we build our utilities in /dev/crashcart/ instead.

[catern]

Hmmmm, interesting... That does seem like a pretty good reason, though maybe you could bind mount over /nix? That should be fine from a Nix perspective, not sure how well it works with container technologies.

[danbst]

Try Nix 2.0, it can place your derivations in custom folder by clever use of chroot, read about --store argument.