Arch Linux

Right now, /etc/profile.d/locale.sh is used to source /etc/locale.conf and export the variables in bourne-compatible login shells. This mostly works, but not all logins spawn a login shell (many display managers) and not everyone uses bash or zsh.

The syntax of locale.conf is simple enough that pam_env is enough to source it, so it could be done in the pam configuration instead. This would be a lot simpler (1 line instead of a script), and more general.

The pam_env man page has the details on what needs to be done (a line like 'session required pam_env.so envfile=/etc/locale.conf'.

This wouldn't be usable for $XDG_CONFIG_HOME/locale.conf, but AFAIK that's an Arch Linux specific extension and you can set the same stuff in ~/.pam_environment. The usefulness of /etc/locale.conf is that systemd uses it too. User sessions will always be within a pam session.

This is from Debian (where systemd got this convention):

$ grep -R pam_env.so /etc/pam.d/
/etc/pam.d/sshd:auth required pam_env.so # [1]
/etc/pam.d/sshd:auth required pam_env.so envfile=/etc/default/locale
/etc/pam.d/cron:session required pam_env.so
/etc/pam.d/cron:session required pam_env.so envfile=/etc/default/locale
/etc/pam.d/su:session required pam_env.so readenv=1
/etc/pam.d/su:session required pam_env.so readenv=1 envfile=/etc/default/locale
/etc/pam.d/login:session required pam_env.so readenv=1
/etc/pam.d/login:session required pam_env.so readenv=1 envfile=/etc/default/locale