Frequently Asked Questions ========================== Nix *** How do I fix: error: querying path in database: database disk image is malformed -------------------------------------------------------------------------------- how nix decides which parts of the environment affect a derivation and its sha256 hash -------------------------------------------------------------------------------------- What are channels and different branches on github? --------------------------------------------------- How do I mirror tarballs? ------------------------- We have a content-addressed tarball mirror at http://tarballs.nixos.org for this purpose. "fetchurl" will automatically use this mirror to obtain files by hash. However: * The mirroring script was not running lately. I've revived it so 16.03 tarballs are mirrored now (https://github.com/NixOS/nixos-org-configurations/commit/a17ccf87deae4fb86639c8d34ab5938edd68d8c4). * The mirroring script only copies tarballs of packages in the Nixpkgs Hydra jobset. Since moreutils is not part of the jobset, it's not mirrored. This can be fixed by adding a meta.platforms attribute to moreutils. Hydra ***** What to do if Hydra is down or unreachable? ------------------------------------------- TODO How do I add a new binary cache? -------------------------------- Using `NixOS`: TODO Using `Nix`: ``` $ echo "trusted-binary-caches = https://hydra.snabb.co" >> /etc/nix/nix.conf $ nix-build helpers/bench.nix --option extra-binary-caches https://hydra.snabb.co` ``` Are there some known impurities in builds? ------------------------------------------ Yes. - CPU (we try hard to avoid compiling native instructions, but rather hardcode supported ones) - current date - FileSystem (ext4 has a known bug creating `empty files on power loss `_) - Kernel - Timing behaviour of the build system (parallel Make not getting correct inputs in some cases)