Commit ad19cee0 authored by nikstur's avatar nikstur
Browse files

nixos/image/repart: assert maximum label length 

The maximum label length is specified by UEFI and enforced/asserted by
systemd-repart. This lets evaluation fail already and give the user
some more information about what's wrong.

Also warn when the suggested label length is exceeded. This serves as a
safety mechanism for using systemd-sysupdate style A/B updates where the
version number is encoded in the label and might not be incrementable
when the maximum label size is reached.
parent 4c397ea6

nixos/modules/image/repart.nix

+38 −0
Original line number Diff line number Diff line
@@ -6,6 +6,8 @@ 
let

  cfg = config.image.repart;



  inherit (utils.systemdUtils.lib) GPTMaxLabelLength;



  partitionOptions = {

    options = {

      storePaths = lib.mkOption {
@@ -224,6 +226,42 @@ in 


  config = {



    assertions = lib.mapAttrsToList (fileName: partitionConfig:

      let

        inherit (partitionConfig) repartConfig;

        labelLength = builtins.stringLength repartConfig.Label;

      in

      {

        assertion = repartConfig ? Label -> GPTMaxLabelLength >= labelLength;

        message = ''

          The partition label '${repartConfig.Label}'

          defined for '${fileName}' is ${toString labelLength} characters long,

          but the maximum label length supported by UEFI is ${toString

          GPTMaxLabelLength}.

        '';

      }

    ) cfg.partitions;



    warnings = lib.filter (v: v != null) (lib.mapAttrsToList (fileName: partitionConfig:

      let

        inherit (partitionConfig) repartConfig;

        suggestedMaxLabelLength = GPTMaxLabelLength - 2;

        labelLength = builtins.stringLength repartConfig.Label;

      in

        if (repartConfig ? Label && labelLength >= suggestedMaxLabelLength) then ''

          The partition label '${repartConfig.Label}'

          defined for '${fileName}' is ${toString labelLength} characters long.

          The suggested maximum label length is ${toString

          suggestedMaxLabelLength}.



          If you use sytemd-sysupdate style A/B updates, this might

          not leave enough space to increment the version number included in

          the label in a future release. For example, if your label is

          ${toString GPTMaxLabelLength} characters long (the maximum enforced by UEFI) and

          you're at version 9, you cannot increment this to 10.

        '' else null

    ) cfg.partitions);



    image.repart =

      let

        version = config.image.repart.version;