Cleaning of $XDG_CACHE_HOME and $XDG_CACHE_HOME/thumbnails

[Bastien Nocera]

On Wed, 2020-02-26 at 13:45 +0100, Benjamin Berg wrote:
> Hi,
> 
> so I looked at gsd-housekeeping the other day. With systemd-
> tempfiles,
> it only has two purposes these days:
> 
>  1. Cleaning $XDG_CACHE_HOME/thumbnails after 30 days
>  2. Cleaning the trash directories after a configurable time
> 
> Currently it also tries to clean /tmp and /var/tmp, but doing so is
> really dangerous compared to just leaving it up to systemd-tempfiles
> (I
> have filed an MR to disable the logic if we are systemd booted).

That's fine.

> 
> Now, systemd-tempfiles can already clean up everything except for the
> trash. And considering that $XDG_CACHE_HOME is non-essential by
> definition, I think it might be sane to use systemd-tempfiles not
> only
> to clean the thumbnails but the entirety of $XDG_CACHE_HOME in the
> future.

It's not "non-essential", it's a cache, which can be regenerated, but
it might be utterly costly to do so. Eg. there are 10 gigs of "cached"
evolution mails in my ~/.cache, 5 gigs of jhbuild builddirs.

Nuking it is a last ditch scenario. You'd avoid backing it up on space
constrained storage, but you'd want to avoid having to regenerate that
cache in most cases.

<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.

> Other thoughts?
> 
> Benjamin
> 
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