Cleaning of $XDG_CACHE_HOME and $XDG_CACHE_HOME/thumbnails

[Benjamin Berg]

Hi,

On Wed, 2020-02-26 at 15:14 +0100, Bastien Nocera wrote:
> Flatpak'ed applications also use a different cache directory, like:
> $ export | grep CACHE
> declare -x XDG_CACHE_HOME="/home/hadess/.var/app/<app-id>/cache"
> 
> I'd say that it might better left well alone, and have something like
> Baobab better signal what each directory is/which application it
> belongs to, to clean it up.

This specification change would only affect the $XDG_CACHE_HOME as set
at login time by pam_systemd (i.e. ~/.cache).

So in principle, Flatpak'ed applications are not affected at all.
However, the logical extension of this proposal would be that
appropriate configurations are shipped inside each Flatpak. Then we
also have a cleanup mechanism there that does not depend on the
application to be run regularly.

I had not thought about that yet. I could imagine Flatpak collecting
the information and doing the simple re-write and dropping it into
~/.config/tmpfiles.d or $XDG_RUNTIME_DIR/tmpfiles.d at login time. And
Flatpak itself could again ship a default to clean .var/app/*/cache by 
default.

Benjamin

> > > <snip>
> > > > Is it reasonable to standardise on the systemd tmpfiles.d
> > > > format?
> > > > Is it OK to clean $XDG_CACHE_HOME after a fixed time period by
> > > > default?
> > > 
> > > I'm guessing that's a no.
> > > 
> > > As for thumbnails, you'd probably get away with checking whether
> > > atime
> > > is actually set on that mount and cleaning up the ones that
> > > haven't
> > > been used.
> > 
> > Benjamin
> 
> 
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