Unverified Commit ab526e04 authored by MidAutumnMoon's avatar MidAutumnMoon
Browse files

nixos/ids: explain *why* uids/gids shouldn't be above "399"

parent 1e9e641a

nixos/modules/misc/ids.nix

+36 −2
Original line number Diff line number Diff line
@@ -356,7 +356,24 @@ in 
      localtimed = 325;

      automatic-timezoned = 326;



      # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!

      # When adding a uid, make sure it doesn't match an existing gid.

      #

      # !!! Don't use uids above "399"! !!!

      #

      # The reason behind this restriction is that, NixOS by default allocates

      # system user UIDs/GIDs in the range of `400..999`. System users/groups

      # created using command like `useradd` will have UID and GID in this range[1].

      #

      # If a newly added ID goes beyond "399", it may conflict with existing

      # system user or group of the same id in someone else's NixOS.

      # This could break their system and make that person upset for a whole day.

      #

      # Sidenote: the default is defined in `shadow` module[2], and the relavent change

      # was made way back in 2014[3].

      #

      # [1]: https://man7.org/linux/man-pages/man5/login.defs.5.html#:~:text=SYS_UID_MAX%20(number)%2C%20SYS_UID_MIN%20(number)

      # [2]: <nixos/modules/programs/shadow.nix>

      # [3]: https://github.com/NixOS/nixpkgs/commit/0e23a175de3687df8232fe118cbe87f04228ff28



      nixbld = 30000; # start of range of uids

      nobody = 65534;
@@ -669,7 +686,24 @@ in 


      # When adding a gid, make sure it doesn't match an existing

      # uid. Users and groups with the same name should have equal

      # uids and gids. Also, don't use gids above 399!

      # uids and gids.

      #

      # !!! Don't use gids above "399"! !!!

      #

      # The reason behind this restriction is that, NixOS by default allocates

      # system user UIDs/GIDs in the range of `400..999`. System users/groups

      # created using command like `useradd` will have UID and GID in this range[1].

      #

      # If a newly added ID goes beyond "399", it may conflict with existing

      # system user or group of the same id in someone else's NixOS.

      # This could break their system and make that person upset for a whole day.

      #

      # Sidenote: the default is defined in `shadow` module[2], and the relavent change

      # was made way back in 2014[3].

      #

      # [1]: https://man7.org/linux/man-pages/man5/login.defs.5.html#:~:text=SYS_UID_MAX%20(number)%2C%20SYS_UID_MIN%20(number)

      # [2]: <nixos/modules/programs/shadow.nix>

      # [3]: https://github.com/NixOS/nixpkgs/commit/0e23a175de3687df8232fe118cbe87f04228ff28



      # For exceptional cases where you really need a gid above 399, leave a

      # comment stating why.