[fedora-virt] guestfish, libguestfs, ext4 and bad perms on /dev/kvm

Richard W.M. Jones rjones at redhat.com
Wed Apr 22 20:17:29 UTC 2009

On Wed, Apr 22, 2009 at 03:20:14PM -0400, Robert P. J. Day wrote:
>   in short, ext4 filesystem support now appears to work, but there's
> still the issue (perhaps addressed earlier) that non-root users don't
> have access to KVM support but, from the perspective of libguestfs,
> does that really matter?

KVM makes things do a lot faster, which is always nice.  You can
do the following:

  # chmod o+rw /dev/kvm

You have to do (just) that command as root, but after that qemu-kvm and
guestfish itself can all be run as non-root, and will benefit from KVM

There is the question of whether it's safe to allow non-root users to
use KVM.  Generally the answer seems to be that it's OK.  But if you
are running a production service, or have lots of untrusted users or
guests, then maybe it's better not to turn this on just yet.

>   anyway, ext4 support is in there so things are working, at least to
> the extent that i've tested it.

> p.s.  i could have sworn i didn't get that /dev/kvm perms error
> yesterday. did something about that change since version 1.0.4?

Yes, libguestfs changed to detect and enable KVM by default.  Before
today it wasn't using KVM at all.


Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
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