Libguestfs - Nov 2019 - RHEL 7 and guestmount of XFS volumes

Hi,

I'm experiencing a weird behavior when tried to use guestmount with a XFS
formatted volume. I have created a RHEL 8 virtual machine using libvirt. I
have retrieved the disk image on a RHEL 7.7 server to mount the image root
filesystem and explore it.

The command returns an error message:

# guestmount -a /disks/jamesdream.qcow2 -m /dev/sda1 /mnt/
libguestfs: error: mount_options: mount exited with status 32: mount: wrong
fs type, bad option, bad superblock on /dev/sda1,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
guestmount: ‘/dev/sda1’ could not be mounted.
guestmount: Did you mean to mount one of these filesystems?
guestmount: /dev/sda1 (xfs)
guestmount: /dev/rhel/root (xfs)
guestmount: /dev/rhel/swap (swap)

I have also run the same command with -x and -v options and the log is
attached.

Seeing that it's not working on RHEL 7, I've tried the same command on
another RHEL 8.1 machine and it works. Looking at libguestfs-tools package
version, it appears that the package on RHEL 7.7 (1.40.2-5.el7_7.2) is more
recent than on RHEL 8.1 (1.38.4-14.module+el8.1.0+4066+0f1aadab). Is that
normal ?

Thanks for your help.

-- 

Fabien Dupont, RHCA

Principal Software Engineer

Red Hat - Migration Engineering <https://www.redhat.com>
<https://red.ht/sig>
<https://redhat.com/summit>

On Mon, Nov 25, 2019 at 12:08:33PM +0100, Fabien Dupont
wrote:
> Hi,
> 
> I'm experiencing a weird behavior when tried to use guestmount with a
XFS
> formatted volume. I have created a RHEL 8 virtual machine using libvirt. I
> have retrieved the disk image on a RHEL 7.7 server to mount the image root
> filesystem and explore it.
> 
> The command returns an error message:
> 
> # guestmount -a /disks/jamesdream.qcow2 -m /dev/sda1 /mnt/
> libguestfs: error: mount_options: mount exited with status 32: mount: wrong
> fs type, bad option, bad superblock on /dev/sda1,
>        missing codepage or helper program, or other error
> 
>        In some cases useful info is found in syslog - try
>        dmesg | tail or so.
> guestmount: ‘/dev/sda1’ could not be mounted.
> guestmount: Did you mean to mount one of these filesystems?
> guestmount: /dev/sda1 (xfs)
> guestmount: /dev/rhel/root (xfs)
> guestmount: /dev/rhel/swap (swap)
> 
> I have also run the same command with -x and -v options and the log is
> attached.
> 
> Seeing that it's not working on RHEL 7, I've tried the same command
on
> another RHEL 8.1 machine and it works. Looking at libguestfs-tools package
> version, it appears that the package on RHEL 7.7 (1.40.2-5.el7_7.2) is more
> recent than on RHEL 8.1 (1.38.4-14.module+el8.1.0+4066+0f1aadab). Is that
> normal ?
Hi Fabien, sadly yes this is normal, it's a kernel "bug"
(disputed):

https://bugzilla.redhat.com/show_bug.cgi?id=1667478

There's a somewhat hacky and definitely not supported workaround:

https://access.redhat.com/solutions/3914591

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW

Thanks. So, I'll stay with RHEL 8. Not a big deal.

On Mon, Nov 25, 2019 at 1:55 PM Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Mon, Nov 25, 2019 at 12:08:33PM +0100, Fabien Dupont wrote:
> > Hi,
> >
> > I'm experiencing a weird behavior when tried to use guestmount
with a XFS
> > formatted volume. I have created a RHEL 8 virtual machine using
libvirt.
> I
> > have retrieved the disk image on a RHEL 7.7 server to mount the image
> root
> > filesystem and explore it.
> >
> > The command returns an error message:
> >
> > # guestmount -a /disks/jamesdream.qcow2 -m /dev/sda1 /mnt/
> > libguestfs: error: mount_options: mount exited with status 32: mount:
> wrong
> > fs type, bad option, bad superblock on /dev/sda1,
> >        missing codepage or helper program, or other error
> >
> >        In some cases useful info is found in syslog - try
> >        dmesg | tail or so.
> > guestmount: ‘/dev/sda1’ could not be mounted.
> > guestmount: Did you mean to mount one of these filesystems?
> > guestmount: /dev/sda1 (xfs)
> > guestmount: /dev/rhel/root (xfs)
> > guestmount: /dev/rhel/swap (swap)
> >
> > I have also run the same command with -x and -v options and the log is
> > attached.
> >
> > Seeing that it's not working on RHEL 7, I've tried the same
command on
> > another RHEL 8.1 machine and it works. Looking at libguestfs-tools
> package
> > version, it appears that the package on RHEL 7.7 (1.40.2-5.el7_7.2) is
> more
> > recent than on RHEL 8.1 (1.38.4-14.module+el8.1.0+4066+0f1aadab). Is
that
> > normal ?
>
> Hi Fabien, sadly yes this is normal, it's a kernel "bug"
(disputed):
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1667478
>
> There's a somewhat hacky and definitely not supported workaround:
>
> https://access.redhat.com/solutions/3914591
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> Fedora Windows cross-compiler. Compile Windows programs, test, and
> build Windows installers. Over 100 libraries supported.
> http://fedoraproject.org/wiki/MinGW
>
>
-- 

Fabien Dupont, RHCA

Principal Software Engineer

Red Hat - Migration Engineering <https://www.redhat.com>
<https://red.ht/sig>
<https://redhat.com/summit>