[libvirt-users] [Libguestfs] Cannot guestmount a Fedora 24 XFS disk.

[Richard W.M. Jones]

On Tue, Aug 09, 2016 at 05:15:34PM +0000, Andre Goree wrote:
> The host is running Ubuntu 12.04 LTS and has the libguestfs package installed -- which, if I'm not mistaken, provides libguestfs-xfs:
> 
> https://launchpad.net/ubuntu/+source/libguestfs

My bad, I didn't read the kernel message closely.  If you look at:

> > mount -o  /dev/vda1 /sysroot/
> > [    1.759120] SGI XFS with ACLs, security attributes, realtime, large block/inode numbers, no debug enabled
> > [    1.762869] XFS (vda1): Version 5 superblock detected. This kernel has EXPERIMENTAL support enabled!
> > [    1.762869] Use of these features in this kernel is at your own risk!
> > [    1.764819] XFS (vda1): Superblock has unknown read-only compatible features (0x1) enabled.
> > [    1.765834] XFS (vda1): Attempted to mount read-only compatible filesystem read-write.
> > [    1.765834] Filesystem can only be safely mounted read only.
> > [    1.767472] XFS (vda1): SB validate failed with error 22.
> > mount: wrong fs type, bad option, bad superblock on /dev/vda1,
> >        missing codepage or helper program, or other error
> >        In some cases useful info is found in syslog - try
> >        dmesg | tail  or so

It's using your host kernel (which for Ubuntu 12.04 is ancient
history) to mount a recently created XFS filesystem (Fedora 24 is from
this year).

This isn't possible because of some new feature or other, and so you
can only mount it in read-only mode.

Hopefully using 'guestmount --ro' will work.  You can check using the
'guestmount -v' and/or '-x' option that the "ro" option is passed by
mount to the kernel.

If not then it'll be accessible via guestfish using the "mount-ro"
command.

Of course this is for reading only.  It's not possible to write unless
you can upgrade your host kernel to something very much newer.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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