[fedora-virt] Re: virt-inspector calling guestfs_umount_all() before launch()?

Richard W.M. Jones rjones at redhat.com
Thu May 28 08:39:30 UTC 2009

On Wed, May 27, 2009 at 05:16:40PM -0500, Charles Duffy wrote:
> Charles Duffy wrote:
>> This is virt-inspector-1.0.34-1.3 on CentOS 5:
>> $ virt-inspector --ro-fish --xml da.qcow2
>> qemu: loading initrd (0x33a576d bytes) at 0x0000000014c4a000
>> umount_all: guestfs_umount_all: call launch() before using this  
>> function at /usr/bin/virt-inspector line 375.
> Running with LIBGUESTFS_DEBUG=1, it appears that this happened due to  
> the guest trying to do ext3 journal recovery against a read-only image.

ext3 tries to do a journal recovery if we mount -o ro ?

> If telling libguestfs to run in read-only mode implied passing the  
> -snapshot flag to qemu, and passing the snapshot=on option to each  
> -drive, this should allow changes to be *temporarily* created (stored to  
> unlinked copy-on-write files for the duration of the run), mooting  
> issues of this kind.

I want to get the ability to mount drives completely read-only into
qemu.  Turns out that it's a bit more complicated than just opening
the underlying file O_RDONLY - we have to communicate this all the way
through IDE / virtio drivers.

But using snapshots actually isn't such a bad idea.  Also works with
previous and current versions of qemu too.


Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.

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