Libguestfs - Feb 2015 - Re: Mounting disk images with ext2 filesystems on RHEL7

On Mon, Feb 16, 2015 at 6:10 PM, Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Mon, Feb 16, 2015 at 06:00:06PM -0500, Leonard Basuino wrote:
> > Hope someone can point me in the right direction.  I don't know if
what I
> > am trying to do should work or not.
> >
> > I have 2 disk images.  One is a VM with an ext2 boot filesystem and
ext4
> > filesystems with the OS loaded.  I am amble to guestmount this with no
> > issue and am able to see the files that are on the ext2 file system.
> >
> > I can also run guestfish on the image, mount the ext2 filesystem, and
> list
> > the files.
> >
> > However, the second image I have is only a boot disk image with just
an
> > ext2 filesystem.
> >
> > guestmount complains that there is no OS and won't mount.
>
> What you really need to do is run:
>
>   virt-filesystems -a second-disk.img --all --long -h
>
> which will tell you what filesystems (etc) are available in the second
> image.
>
> The only filesystem is /dev/sda1 of type ext2

> > guestfish complains "...wrong fs type, bad option, bad
superblock...".
>
> Try using guestfish -v -x flags to provide extra information about
> this error.  See:
>
> http://libguestfs.org/guestfs-faq.1.html#debug
>
I get the following debug info:

mount -o /dev/sda1 /
[ <time> ] EXT4-fs (sda1): mounting ext2 file system using the ext4
subsystem
[ <time> ] EXT4-fs (sda1): bad geometry: block count 104388 exceeds size
of
device (103408 blocks)
mount: wrong fs type, bad option, bad superblock on /dev/sda1
....

also, trying to mount the image with:
mount -t ext2 <image> <mount point>
returns:
mount: wrong fs type, bad option, bad superblock on /dev/loop0
...
the end of dmesg has:
[<time>] EXT4-fs (loop0): VFS: Can't find ext4 filesystem

This has me wondering because the debug messages from guestfish -v -x
indicate it is mouting ext2 with ext4.
EXT4-fs (sdb): mounting ext2 filesystem using the ext4 subsystem

So is the problem that there is no ext4 filesystem in the image and RHEL 7
is having issues with it?

> Also, what version of libguestfs and where did you get it from?
>
> version 1.22.6-22, came with RHEL 7
> > Should I be able to mount a boot disk image with guestmount?
>
> Yes, libguestfs aims to be able to access any disk image, and mostly
> we have achieved that.  Whether it is bootable or not wouldn't
> normally matter.
>
> > I suspect I'll have to use the -m (mount) option and not -i (as I
did for
> > the image with an OS), but that failed too even though I passed in the
fs
> > type of ext2,
>
> `-i' invokes inspection:
>
> http://libguestfs.org/guestfs.3.html#inspection
>
> Inspection is an optional convenience feature, and you can access disk
> images without it, but then you need to know what filesystems you want
> to mount (eg. using 'virt-filesystems' -- see above).
>
> > Why would I be able to mount, via guestfish, the ext2 in the first
image
> > (with other filesystems of type ext4) but not the disk image with only
an
> > ext2 filesystem?
>
> I've no idea, but for more information you can enable debugging at run
> time:
>
> http://libguestfs.org/guestfs-faq.1.html#debug
>
> Rich.
>
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-p2v converts physical machines to virtual machines.  Boot with a
> live CD or over the network (PXE) and turn machines into KVM guests.
> http://libguestfs.org/virt-v2v
>

In data martedì 17 febbraio 2015 13:37:55, Leonard Basuino ha
scritto:
> On Mon, Feb 16, 2015 at 6:10 PM, Richard W.M. Jones
<rjones@redhat.com>
> wrote:
> 
> > On Mon, Feb 16, 2015 at 06:00:06PM -0500, Leonard Basuino wrote:
> > > Hope someone can point me in the right direction.  I don't
know if what I
> > > am trying to do should work or not.
> > >
> > > I have 2 disk images.  One is a VM with an ext2 boot filesystem
and ext4
> > > filesystems with the OS loaded.  I am amble to guestmount this
with no
> > > issue and am able to see the files that are on the ext2 file
system.
> > >
> > > I can also run guestfish on the image, mount the ext2 filesystem,
and
> > list
> > > the files.
> > >
> > > However, the second image I have is only a boot disk image with
just an
> > > ext2 filesystem.
> > >
> > > guestmount complains that there is no OS and won't mount.
> >
> > What you really need to do is run:
> >
> >   virt-filesystems -a second-disk.img --all --long -h
> >
> > which will tell you what filesystems (etc) are available in the second
> > image.
> >
> 
> 
> > The only filesystem is /dev/sda1 of type ext2
> 
> 
> 
> > > guestfish complains "...wrong fs type, bad option, bad
superblock...".
> >
> > Try using guestfish -v -x flags to provide extra information about
> > this error.  See:
> >
> > http://libguestfs.org/guestfs-faq.1.html#debug
> >
> 
> I get the following debug info:
> 
> mount -o /dev/sda1 /
> [ <time> ] EXT4-fs (sda1): mounting ext2 file system using the ext4
> subsystem
> [ <time> ] EXT4-fs (sda1): bad geometry: block count 104388 exceeds
size of
> device (103408 blocks)
> mount: wrong fs type, bad option, bad superblock on /dev/sda1
> ....
This might mean that the partition has been resized to a smaller size,
but without updating the partition table. Is that the case?

Can you please post the output of the guestfish command
`sfdisk-l /dev/sda`?
> also, trying to mount the image with:
> mount -t ext2 <image> <mount point>
> returns:
> mount: wrong fs type, bad option, bad superblock on /dev/loop0
> ...
> the end of dmesg has:
> [<time>] EXT4-fs (loop0): VFS: Can't find ext4 filesystem
> 
> This has me wondering because the debug messages from guestfish -v -x
> indicate it is mouting ext2 with ext4.
> EXT4-fs (sdb): mounting ext2 filesystem using the ext4 subsystem
In recent (well, few years...) Linux versions the ext4 filesystems
takes care of ext2 and ext3 versions as well, so the above message
is correct.
> So is the problem that there is no ext4 filesystem in the image and RHEL 7
> is having issues with it?
I'm not sure what you mean here, can you please rephrase?

Thanks,
-- 
Pino Toscano

On Tue, Feb 17, 2015 at 01:37:55PM -0500, Leonard Basuino
wrote:
> I get the following debug info:
> 
> mount -o /dev/sda1 /
> [ <time> ] EXT4-fs (sda1): mounting ext2 file system using the ext4
> subsystem
> [ <time> ] EXT4-fs (sda1): bad geometry: block count 104388 exceeds
size of
> device (103408 blocks)
> mount: wrong fs type, bad option, bad superblock on /dev/sda1
It looks as if the image is properly corrupt.  My suggestion
is to try 'virt-rescue' on it.
> This has me wondering because the debug messages from guestfish -v -x
> indicate it is mouting ext2 with ext4.
> EXT4-fs (sdb): mounting ext2 filesystem using the ext4 subsystem
This is just the way that RHEL 7 works. ie. CONFIG_EXT4_USE_FOR_EXT23=y
is now always used.  http://lwn.net/Articles/378913/

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top

On Wed, Feb 18, 2015 at 4:51 AM, Pino Toscano <ptoscano@redhat.com> wrote:
> In data martedì 17 febbraio 2015 13:37:55, Leonard Basuino ha scritto:
> > On Mon, Feb 16, 2015 at 6:10 PM, Richard W.M. Jones
<rjones@redhat.com>
> > wrote:
> >
> > > On Mon, Feb 16, 2015 at 06:00:06PM -0500, Leonard Basuino wrote:
> > > > Hope someone can point me in the right direction.  I
don't know if
> what I
> > > > am trying to do should work or not.
> > > >
> > > > I have 2 disk images.  One is a VM with an ext2 boot
filesystem and
> ext4
> > > > filesystems with the OS loaded.  I am amble to guestmount
this with
> no
> > > > issue and am able to see the files that are on the ext2 file
system.
> > > >
> > > > I can also run guestfish on the image, mount the ext2
filesystem, and
> > > list
> > > > the files.
> > > >
> > > > However, the second image I have is only a boot disk image
with just
> an
> > > > ext2 filesystem.
> > > >
> > > > guestmount complains that there is no OS and won't
mount.
> > >
> > > What you really need to do is run:
> > >
> > >   virt-filesystems -a second-disk.img --all --long -h
> > >
> > > which will tell you what filesystems (etc) are available in the
second
> > > image.
> > >
> >
> >
> > > The only filesystem is /dev/sda1 of type ext2
> >
> >
> >
> > > > guestfish complains "...wrong fs type, bad option, bad
> superblock...".
> > >
> > > Try using guestfish -v -x flags to provide extra information
about
> > > this error.  See:
> > >
> > > http://libguestfs.org/guestfs-faq.1.html#debug
> > >
> >
> > I get the following debug info:
> >
> > mount -o /dev/sda1 /
> > [ <time> ] EXT4-fs (sda1): mounting ext2 file system using the
ext4
> > subsystem
> > [ <time> ] EXT4-fs (sda1): bad geometry: block count 104388
exceeds size
> of
> > device (103408 blocks)
> > mount: wrong fs type, bad option, bad superblock on /dev/sda1
> > ....
>
> This might mean that the partition has been resized to a smaller size,
> but without updating the partition table. Is that the case?
>
> Can you please post the output of the guestfish command
> `sfdisk-l /dev/sda`?
>
(ok, I have to type it so pardon any typos)

Disk /dev/sda: 101 cylinders, 64 heads, 32 sectors/track
Units: cylinders of 1048576 bytes, blocks of 1024 bytes, counting from 0

   Device  Boot  Start          End     #cyls       #blocks    Id  System
/dev/sda1     *         0+       100         101-      103408    83  Linux
/dev/sda2               0             -             0                0
0  Empty
 /dev/sda3               0             -             0                0
0  Empty
 /dev/sda3               0             -             0                0
0  Empty

>
> > also, trying to mount the image with:
> > mount -t ext2 <image> <mount point>
> > returns:
> > mount: wrong fs type, bad option, bad superblock on /dev/loop0
> > ...
> > the end of dmesg has:
> > [<time>] EXT4-fs (loop0): VFS: Can't find ext4 filesystem
> >
> > This has me wondering because the debug messages from guestfish -v -x
> > indicate it is mouting ext2 with ext4.
> > EXT4-fs (sdb): mounting ext2 filesystem using the ext4 subsystem
>
> In recent (well, few years...) Linux versions the ext4 filesystems
> takes care of ext2 and ext3 versions as well, so the above message
> is correct.
>
> > So is the problem that there is no ext4 filesystem in the image and
RHEL
> 7
> > is having issues with it?
>
> I'm not sure what you mean here, can you please rephrase?
>
I was wondering if the message indicated it was looking for ext4 in the
image which doesn't exist?
I verified that the same image mounts without issue on a RHEL 6 box but not
on a RHEL 7 box.
>
> Thanks,
> --
> Pino Toscano
>
> _______________________________________________
> Libguestfs mailing list
> Libguestfs@redhat.com
> https://www.redhat.com/mailman/listinfo/libguestfs
>

On Wed, Feb 18, 2015 at 6:52 AM, Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Tue, Feb 17, 2015 at 01:37:55PM -0500, Leonard Basuino wrote:
> > I get the following debug info:
> >
> > mount -o /dev/sda1 /
> > [ <time> ] EXT4-fs (sda1): mounting ext2 file system using the
ext4
> > subsystem
> > [ <time> ] EXT4-fs (sda1): bad geometry: block count 104388
exceeds size
> of
> > device (103408 blocks)
> > mount: wrong fs type, bad option, bad superblock on /dev/sda1
>
> It looks as if the image is properly corrupt.  My suggestion
> is to try 'virt-rescue' on it.
>
> virt-rescue --suggest -a <image>
Inspecting the virtual machine or disk image ...

This disk contains one or more filesystems, but we don't recognize any
operating system.  You can use these mount commands in virt-rescue (at
the
><rescue> prompt) to mount these filesystems.
# /dev/sda1 has type 'ext2'
mount /dev/sda1 /sysroot

So I tried ...
><rescue> mount /dev/sda1 /sysroot
[<time>] EXT4-fs (sda1): mounting ext2 filesystem using the ext4 subsystem
[<time>] EXT4-fs (sda1): bad geometry: block count 104388 exceeds size of
device (103408 blocks)
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

I don't think the image is corrupt because a colleague is able to mount it
with guestfish on a RHEL 6 box.

> > This has me wondering because the debug messages from guestfish -v -x
> > indicate it is mouting ext2 with ext4.
> > EXT4-fs (sdb): mounting ext2 filesystem using the ext4 subsystem
>
> This is just the way that RHEL 7 works. ie. CONFIG_EXT4_USE_FOR_EXT23=y
> is now always used.  http://lwn.net/Articles/378913/
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-top is 'top' for virtual machines.  Tiny program with many
> powerful monitoring features, net stats, disk stats, logging, etc.
> http://people.redhat.com/~rjones/virt-top
>