Xen users - May 2009 - can the root password be recovered from a DomU

Just curious if anyone knows this. If you loose the root password on a Linux
box, you can just boot from CDRom, mount the root partition and edit
/etc/shadow.
Is it possible to do something similar with a DomU.

I tried:
mount -o loop mydisk.img /mnt
but I got an error saying something like "you must specify a filesystem
type"
mount -o loop -t ext3 mydisk.img /mnt does NOT work either (I''ve also
tried
moving the ''-t ext3'' part but no go)


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Assuming your image file has been partitioned, you''ll need to specify 
the offset to the start of the partition you want to mount. Otherwise 
you''re trying to mount the partition table as a filesystem, which is
why
you see the "must specify a filesystem type" error.

What you want (assuming you want the first partition, which starts at 
block 62 * 512 bytes/block) is:

mount -o loop,offset=$((62*512) mydisk.img /mnt

A few quick references:
http://darkdust.net/writings/diskimagesminihowto
http://www.openclose.it/creare_e_usare_un_disco_immagine.do


Kevin McKeon wrote:
> Just curious if anyone knows this. If you loose the root password on a 
> Linux box, you can just boot from CDRom, mount the root partition and 
> edit /etc/shadow.
> Is it possible to do something similar with a DomU.
> 
> I tried:
> mount -o loop mydisk.img /mnt
> but I got an error saying something like "you must specify a
filesystem
> type"
> mount -o loop -t ext3 mydisk.img /mnt does NOT work either (I''ve
also
> tried moving the ''-t ext3'' part but no go)
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You can try this from dom0 (in this example the domU uses LVM): 

kpartx -av /var/lib/xen/images/vm2.img
	You may need to install kpartx yourself, not sure if it comes "free
inside" (yum search kpartx on CentOs)
	maps disk partitions to device table entries
	uses losetup to create loop devices to disks

vgscan
	To find volume groups on the newly mapped disk

vgchange -ay VM_VG00
	Activate the volume group you need, VM_VG00 is just an example...

mount /dev/VM_VG00/VM_LV00 /mnt
	Mount the filesystem you want, 
	Make your changes

umount /mnt
vgchange -an VM_VG00
kpartx -dv /var/lib/xen/images/vm2.img

	To unwind things.

Joe

----- Original Message -----
> From: xen-users-bounces@lists.xensource.com
<xen-users-bounces@lists.xensource.com>
> To: Xen-users@lists.xensource.com <Xen-users@lists.xensource.com>,
Kevin McKeon <kevin.w.mckeon@gmail.com>
> Sent: Friday, May 22, 2009 1:03:16 PM GMT-0800 America;Los_Angeles
> Subject: [Xen-users] can the root password be recovered from a DomU
> > Just curious if anyone knows this. If you loose the root password on a
> Linux box, you can just boot from CDRom, mount the root partition and 
> edit /etc/shadow.
> Is it possible to do something similar with a DomU.
> 
> I tried:
> mount -o loop mydisk.img /mnt
> but I got an error saying something like "you must specify a 
> filesystem type"
> mount -o loop -t ext3 mydisk.img /mnt does NOT work either (I''ve
also
> tried moving the ''-t ext3'' part but no go)
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Also you can mount the image, mount -o loop disk.img lala/
then chroot to the mounted directory chroot lala
and passwd to change the password


-- 
antonis kouzoupis


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How can I do this on a file
DomU config file

disk = [ "tap:aio:/mnt/Domu/server.dsk,xvda,w" ]

I can mount this server.dsk file''s partitions  using losetup and kpartx

But how to mount this whole file in a single directory to use chroot


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On Mon, May 25, 2009 at 12:19 PM, Tanuj Bansal <bansal.tanuj83@gmail.com>
wrote:
> How can I do this on a file
> DomU config file
> disk = [ "tap:aio:/mnt/Domu/server.dsk,xvda,w" ]
>
> I can mount this server.dsk file''s partitions  using losetup and
kpartx
> But how to mount this whole file in a single directory to use chroot
With that setup, you don''t mount the whole file. You mount its
partitions (which apparently you already do).
So for example if your domU root is on xvda1, and you use losetup and
kpartx to make it available as /dev/mapper/loop0p1, and you already
mount it on /mnt, you simply have to run "chroot /mnt"

Other setups require you to mount the whole file, or use LVM, but from
what you describe you don''t need those.

-- 
Fajar

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Try to use this tool :
http://www.albar.fr/downloads/vbdmount.py

2009/5/22 Kevin McKeon <kevin.w.mckeon@gmail.com>
> Just curious if anyone knows this. If you loose the root password on a
> Linux box, you can just boot from CDRom, mount the root partition and edit
> /etc/shadow.
> Is it possible to do something similar with a DomU.
>
> I tried:
> mount -o loop mydisk.img /mnt
> but I got an error saying something like "you must specify a
filesystem
> type"
> mount -o loop -t ext3 mydisk.img /mnt does NOT work either (I''ve
also tried
> moving the ''-t ext3'' part but no go)
>
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>

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