users: persistence (mutableUsers)

[rehno-lindeque]

Persists user credentials.

Take note of the issue with using passwd which is explained in this thread NixOS/nixpkgs#3192

It appears that a solution is to use passwd with --root to chroot into the correct directory. (this is mentioned in the description for this option).

[rehno-lindeque]

It seems difficult to enable this option on a running system. Potentially it might be possible to do this when using nixos-install, but it's difficult after since nix needs /etc/passwd and /etc/shadow to activate.

nix-community/impermanence#88 may be required to make this work properly.

[rehno-lindeque]

Temporary workaround I tried for testing this in the mean time

mv /etc/passwd /persistent/passwd
mv /etc/shadow /persistent/shadow
ln -s /nix/persistent/etc/passwd /etc/passwd
ln -s /nix/persistent/etc/shadow /etc/shadow

Unfortunately this doesn't work because these files appear to be replaced while switching configurations (presumably by https://github.com/NixOS/nixpkgs/blob/e9bdd5fa74bcbae7d0b587bc4c12d2353fd92611/nixos/modules/config/update-users-groups.pl#L280-L310)