[fedora-virt] libguestfs under Debian / Ubuntu

Emre Erenoglu erenoglu at gmail.com
Fri Jun 12 08:51:09 UTC 2009

On Fri, Jun 12, 2009 at 10:34 AM, Richard W.M. Jones <rjones at redhat.com>wrote:

> On Fri, Jun 12, 2009 at 01:14:07AM +0200, Emre Erenoglu wrote:
> > On Thu, Jun 11, 2009 at 10:24 PM, Daniel P. Berrange<berrange at redhat.com>
> wrote:
> > >
> > > that repo. libguestfs uses a febootstrap to install a custom Fedora 11
> > > appliance which it boots within QEMU in order to access the
> filesystems.
> >
> > If the sole purpose of febootstrap is to install a custom F11
> > appliance to boot in qemu, why don't we prepare this image beforehand,
> > put it somewhere on the web, so that libguestfs can just use it
> > without needing to build this appliance again in each machine with
> > febootstrap or debootstrap?
> We want you to be able to build everything from source.  Also it
> allows you to customize the appliance by editing the script that
> builds it (eg. leaving out a feature or adding other kernel modules).

> In any case, febootstrap can build the appliance in under 3 minutes on
> my machine, so this is hardly a problem for libguestfs.

OK I see now. I would wish that if the configure script is not able to find
febootstrap, it would fall back into using a pre-cooked generic swiss army
knife image file instead. That would make libguestfs pretty trivial to
package for our distro or others, without needing to package yum and
febootstrap etc.

> I read the documentation of libguestfs, but still didn't understand
> > very well why we need to boot an OS within qemu for accessing guest
> > file systems. Can't we just use loop devices, kpartx and lvm tools?
> Because this would require root, and the point of libguestfs is that
> nothing needs to be root.  'libguestfs.so' is a plain library - you
> could link it to your webserver running as nobody.nobody, and it still
> works.  Using loop devices has other disadvantages: it's liable to
> leave temporary mounts & devices around if something fails, and it
> doesn't work at all if there are conflicting VG names.

OK, thanks a lot for this insight. I would say "why not use policykit when
privilege is needed, or mount images with fuse etc. ", but the possibility
to link to a webserver may not work this way :)  Anyway, I'm sure you
considered all these options previously, sorry for taking your time to ask
these again :)   You know, my only problem is with febootstrap and I'm
trying to find a way out of this dependency.

Thanks again,

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