gistfile1.txt

# Option definition
extraAutoPlugins = mkOption {
  default = [];
  type = with types; listOf path;
}

# Implementation detail; ${extraPluginDir} is referenced from a shell script that
# scans that directory for plugins at unit startup time.
extraPluginDir = pkgs.stdenv.mkDerivation {
  name = "munin-extra-plugins.d";
  buildCommand = ''
    mkdir $out
    ${if nodeCfg.extraAutoPlugins == []
      then "true"
      else "cp -a -t $out/ ${toString nodeCfg.extraAutoPlugins}"}
  '';
};

# configuration.nix entry
services.munin-node.extraAutoPlugins = [
  /usr/src/munin-contrib/plugins/zfs/zfs_usage_
  /usr/src/munin-contrib/plugins/zfs/zpool_iostat_
];

# Output of builder
building '/nix/store/l8lkdprmy17ym0nhj7gn5gpw333q73fr-munin-extra-plugins.d.drv'...
cp: cannot stat '/usr/src/munin-contrib/plugins/zfs/zfs_usage_': No such file or directory
cp: cannot stat '/usr/src/munin-contrib/plugins/zfs/zpool_iostat_': No such file or directory