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Re: [fedora-virt] ANNOUNCE: Augeas support added to libguestfs



On Sun, Apr 12, 2009 at 08:40:30AM +0200, Ján ONDREJ (SAL) wrote:
> On Sat, Apr 11, 2009 at 11:41:14PM +0100, Richard W.M. Jones wrote:
> > http://et.redhat.com/~rjones/libguestfs/guestfs.3.html
> 
> I just looked against documentation. Can you build this for Fedora 10 i386?
> Trying to rebuild your src.rpm in mock, but there an unmet dependencies.

What are the missing deps?  You need to have febootstrap and a patched
version of fakechroot (from
http://et.redhat.com/~rjones/febootstrap/files/).  Everything should
be covered by the BuildRequires in the src rpm, unless I've missed
something.

> > I guess you understand that libguestfs doesn't work (or at least, not
> > consistently) with live virtual machines.  You can certainly use
> > libguestfs to take read-only peeks at the live VM's disk image, but
> > the results you get won't necessarily be correct.  Although in the
> > virt-df case, which is similar, in practice the results are fine.
> 
> Yes, I know.

One extra thing I should mention is that I will need to patch qemu to
make this really safe.  Qemu always tries to open the block devices
with O_RDWR [actually, I should say that the qemu code is very
confusing here, but at least this is what I think it does].  I need to
add a patch to qemu so that we can force it to open a drive in
O_RDONLY mode, eg:

  qemu -drive foo,readonly

And then add the corresponding call guestfs_add_drive_ro.

[...]

I guess for the rest what you need is some sort of coordination of
guestfs & (eg) libvirt.  Send to VM the 'lvcreate -s' command [how?],
sync, pause it, take snapshot, resume it.  Coordinating that so you
get something consistent is going to be tricky.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
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