From 035200717b06ba42abb623d6cebc049acdea73aa Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Domen=20Ko=C5=BEar?= Date: Fri, 20 May 2016 16:24:40 +0100 Subject: [PATCH] update FAQ --- source/faq.rst | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/source/faq.rst b/source/faq.rst index a65d5fe..ec765ba 100644 --- a/source/faq.rst +++ b/source/faq.rst @@ -1,4 +1,67 @@ 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)