[fhs-discuss] user-specific directories in /run

[Tollef Fog Heen]

]] Lennart Poettering 

| UH? Why? There's really no point in running old kernels on new
| distributions. The other way round might make more sense...

AIUI, you can't use a pvops-based Xen kernel on older Xen hypervisors,
so if your dom0 is RHEL5, for instance you can't use a too new domU or
it won't run.  (This is all repeated from people who do use Xen, I don't
use it myself and have not verified the claims, but they don't seem to
be completely unreasonable from how I understand Xen works.)

[...]

| > > > - /run/user won't be cleaned by default either.
| > > 
| > > Please read the XDG_RUNTIME_DIR spec. Its a *MUST* that this directory
| > > is removed after a complete logout.
| > 
| > I have read it.  In the context of the FHS, I don't think the text of
| > the spec means much.  It's fine to say "must", but if a session is
| > killed unexpectedly it can still fail to clean up despite what the
| > spec states, and this needs to be considered.
| 
| No. In systemd (git) this cannot happen.

While systemd is nice and good, it'd be be useful to not leave other
init systems instantly buggy when releasing FHS 3.0 because they lag
somewhat behind.  I think it's important that the FHS allows for
distributions to be able to innovate at the same time as it actually
documenting existing practice, not just how an ideal system would work.

[...]

| > As mentioned in other mails: /run /should/ be on a tmpfs, but this
| > is *not* guaranteed.  It could be just a regular filesystem.  In
| > consequence, we can not provide the guarantees you desire, even
| > on plain Linux kernels--consider embedded systems with low memory
| > and no swap where a tmpfs is too expensive, for example.
| 
| On systemd /run is guaranteed to be tmpfs. I think the tmpfs being too
| expensive claim is a myth you are simply using to retroactively justify
| Debian's non-sensical configurability choices. Such a problem does not
| really exist.

The point of having /run not be a tmpfs would post-mortem debuggability,
not the cost of having a tmpfs mount.

-- 
Tollef Fog Heen
UNIX is user friendly, it's just picky about who its friends are