[Libguestfs] guestmount failing to mount a qcow image

[Richard W.M. Jones]

On Thu, Dec 08, 2011 at 04:49:08PM +0000, Pádraig Brady wrote:
> # guestmount --rw -a /tmp/disk -i /tmp/tmplFlBCc
> libguestfs: error: mount_options: mount_options_stub: /dev/root: No
> such file or directory

This image works OK with libguestfs 1.14/1.15.  I suspect the commit
you need to make it work is:

  commit 917f947590c92318fee2545ba88245d0de012e31
  Author: Richard W.M. Jones <rjones at redhat.com>
  Date:   Fri Sep 16 15:26:20 2011 +0100

    inspection: Handle /dev/root in /etc/fstab.
    
    This means "the device that holds /etc/fstab", so map it correctly.
    
    This fixes support for ttylinux and also some other guests that use
    /dev/root instead of a real device name.

The bigger issue here for OpenStack is how to recover gracefully when
inspection fails.  Even though guestmount -i doesn't work on the older
libguestfs, you could still have used explicit -m option(s).  You
would have to know somehow which filesystem(s) are available and which
you want to modify.  That is information you can get from the API
(g.list_filesystems) or using virt-filesystems.  It's reasonable, if
there is only one filesystem in the image, to just mount that one.
What's less clear is what should happen if there are multiple
filesystems: that information would have to be passed down from the
user through OpenStack.

Rich.

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