[bug#62357] [PATCH] services: base: add pam-mount-volume support for greetd

[Brian Cully]

Brian Cully <bjc@spork.org> writes:

> This patch lets users create mounts automatically on login with 
> the greetd
> service by adding `pam-mount-volume' records via the 
> `extra-pam-mount-volumes'
> field of `greetd-configuration'.
>
> The existing rules for XDG_RUNTIME_DIR have been migrated to
> `%base-pam-mount-volumes' and are installed by default.
>
> * gnu/services/base.scm (<pam-mount-volume>): new record
> (pam-mount-volume->sxml): new procedure
> (%base-pam-mount-volumes): new variable
> (greetd-pam-mount-rules): new function
> (%greetd-pam-mount-rules): removed variable
> (<greetd-configuration>): new field `extra-pam-mount-volumes'

I know this patch will need documentation, but I've also assumed 
there'll be some discussion around whether or not this is the best 
way to proceed, so I'm delaying writing it until there's 
consensus.

FWIW, the main use-case of this patch, for me, is auto-mounting 
samba shares from a NAS which requires authentication. By using 
the PAM mount facility, as long as my local and remote credentials 
match, everything happens automatically at login without needing 
to type my password twice, and this lets login scripts use the 
remote services as well.

I'm sure there are countless other ways to use it, but this is 
mine.

It would be nice to have this more generic, since pam-mount isn't 
specifically tied to greetd, but it seems like greetd is the only 
thing in Guix that uses it currently, so that's why that's the 
only hook I've added. I've named the various symbols to express 
that they belong to PAM, generally, or greetd, specifically.

-bjc