motd-legal files don't respect XDG_CACHE_HOME

[Sense Egbert Hofstede]

Binary package hint: base-files

The files $XDG_CACHE_HOME/motd.legal-displayed and $XDG_CACHE_HOME/motd/legal-displayed don't respect the value of XDG_CACHE_HOME, they will always be stored in ~/.cache.

[Dustin Kirkland  (kirkland)]

This would actually need to be changed in pam's pam_motd module. See the patch: ./debian/patches-applied/pam_motd-legal-notice in the pam source package.

I'm not volunteering to fix this, but I am triaging this bug and marking it wishlist, if an enterprising ubuntu user/developer comes along with a better patch, I'll gladly review and sponsor ;-)

[Steve Langasek (vorlon)]

What is the actual use case for making the directory motd.legal-displayed is written to configurable? This seems only to introduce the risk of accidentally displaying the motd multiple times if the target of $XDG_CACHE_HOME changes (or is unset), and as the file is a 0-byte stamp file there should be no concerns about impacting the size of disk backups. Where do you want this file instead of ~/.cache, and why?

[John Drinkwater (johndrinkwater)]

Reasons to want this ‘configurable’ is to match the rest of the system, as this is one of the few remaining binaries that writes into ~/.cache
john@joran ~ ❯ tree .cache
.cache
├── motd.legal-displayed
└── upstart

As everything else already behaves:
john@joran ~ ❯ set | grep XDG_.*_HOME
XDG_CACHE_HOME=/home/john/settings/cache
XDG_CONFIG_HOME=/home/john/settings/config
XDG_DATA_HOME=/home/john/settings/data
XDG_STATE_HOME=/home/john/settings/state
john@joran ~ ❯ tree $XDG_CONFIG_HOME | wc
   2525 11435 126830

Current solution is having this module not run instead.