[Libguestfs] [PATCH virt-v2v] v2v: Allow temporary directory to be set on a global basis.

[Daniel P. Berrangé]

On Tue, Apr 07, 2020 at 02:33:20PM +0200, Pino Toscano wrote:
> On Tuesday, 7 April 2020 14:18:47 CEST Richard W.M. Jones wrote:
> > On Tue, Apr 07, 2020 at 01:25:02PM +0200, Pino Toscano wrote:
> > > The important thing is still that that you need to have space for the
> > > temporary files somewhere: be it /var/tmp, /mnt/scratch, whatever.
> > > Because of this, and the fact that usually containers are created
> > > fresh, the cache of the supermin appliance starts to make little sense,
> > > and then a very simple solution is to point libguestfs to that extra
> > > space:
> > > 
> > >   $ dir=$(mktemp --tmpdir -d /path/to/big/temporary/space/libguestfs.XXXXXX)
> > >   $ export LIBGUESTGS_CACHEDIR=$dir
> > >   $ export TMPDIR=$dir  # optionally
> > >   $ libguestfs-test-tool
> > >   [etc]
> > >   $ rm -rf $dir
> > > 
> > > Easy to use, already doable, solves all the issues.
> > 
> > So AIUI there are a few problems with this (although I'm still
> > investigating and trying to make a local reproducer):
> > 
> >  - The external large space may be on NFS, with the usual problems
> >    there like root_squash, no SELinux labels, slowness.  This means
> >    it's not suitable for the appliance, but might nevertheless be
> >    suitable for overlay files.
> 
> If that is the only big storage space attached to a container, I do
> not see any alternative than use it, with all the caveats associated.
> 
> Also, if we take as possible scenario the situation where /var/tmp is
> not that big, then we need to consider that may not be big enough to
> even store the cached supermin appliance (which is more than
> 300/350MB).

In another message in this thread, Rich indicates the appliance is
being built at the time the container image itself is built. As such
the appliance will already be present in /var/tmp when the container
starts, so there's no disk space issue for it. The issue of lack of
space only applies to files created after the container is running.


Regards,
Daniel
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