nixpkgs/nixos/modules/installer/cd-dvd/channel.nix
Tuomas Tynkkynen 60788745c9 channel.nix: Use filterSource to exclude unnecessary files from nixpkgs
Currently, if you try to build a NixOS config including channel.nix, e.g.:

nix-build -I nixpkgs=. -I nixos-config=nixos/modules/installer/cd-dvd/installation-cd-minimal.nix nixos -A config.system.build.isoImage

twice in a row, you end up with two different build results. This is
caused by the 'result' symlink of the first build affecting the channel
contents of the second build.

If we use filterSource with a predicate that ignores the 'result'
symlinks, the problem is gone. Do the same thing for VIM/Emacs
swap/backup files to avoid even more 'spurious' rebuilds.

Additionally, filter out the '.git' directory at the same time, as we
'rm -rf' it from the result anyway. This avoids a considerable amount of
unnecessary file I/O copying and deleting the .git directory.
2017-03-25 01:42:28 +02:00

55 lines
2.0 KiB
Nix

# Provide an initial copy of the NixOS channel so that the user
# doesn't need to run "nix-channel --update" first.
{ config, lib, pkgs, ... }:
with lib;
let
# Do not include these things:
# - The '.git' directory
# - Result symlinks from nix-build ('result', 'result-2', 'result-bin', ...)
# - VIM/Emacs swap/backup files ('.swp', '.swo', '.foo.swp', 'foo~', ...)
filterFn = path: type: let basename = baseNameOf (toString path); in
if type == "directory" then basename != ".git"
else if type == "symlink" then builtins.match "^result(|-.*)$" basename == null
else builtins.match "^((|\..*)\.sw[a-z]|.*~)$" basename == null;
nixpkgs = builtins.filterSource filterFn pkgs.path;
# We need a copy of the Nix expressions for Nixpkgs and NixOS on the
# CD. These are installed into the "nixos" channel of the root
# user, as expected by nixos-rebuild/nixos-install. FIXME: merge
# with make-channel.nix.
channelSources = pkgs.runCommand "nixos-${config.system.nixosVersion}"
{ }
''
mkdir -p $out
cp -prd ${nixpkgs} $out/nixos
chmod -R u+w $out/nixos
if [ ! -e $out/nixos/nixpkgs ]; then
ln -s . $out/nixos/nixpkgs
fi
echo -n ${config.system.nixosVersionSuffix} > $out/nixos/.version-suffix
'';
in
{
# Provide the NixOS/Nixpkgs sources in /etc/nixos. This is required
# for nixos-install.
boot.postBootCommands = mkAfter
''
if ! [ -e /var/lib/nixos/did-channel-init ]; then
echo "unpacking the NixOS/Nixpkgs sources..."
mkdir -p /nix/var/nix/profiles/per-user/root
${config.nix.package.out}/bin/nix-env -p /nix/var/nix/profiles/per-user/root/channels \
-i ${channelSources} --quiet --option build-use-substitutes false
mkdir -m 0700 -p /root/.nix-defexpr
ln -s /nix/var/nix/profiles/per-user/root/channels /root/.nix-defexpr/channels
mkdir -m 0755 -p /var/lib/nixos
touch /var/lib/nixos/did-channel-init
fi
'';
}