Re: [Xen-users] resetting lost root password on a xen guest

[Steven Timm <timm@xxxxxxxx>]

On Tue, 30 Oct 2007, Liam Kirsher wrote:

> Steven, why do you write "being sure to fsck it afterwards" ? Is that
> important?
I don't have much experience with Xen but I did see an
error like you described below, and after making it a point
to fsck domU file systems after I unmounted them from dom0
I haven't seen the problem again.

Steve Timm


> The reason I ask is that I had a domU filesystem get corrupted, and I
> don't know how it happened.
> It was not all that important in that it was easy to recreate, being
> just my stock CentOS 5 template + bind.
> But, just the same, I'd like to know how it happened!  Interestingly,
> Xen never had a problem creating the domU.  However, my attempts to
> mount it (after shutting down the domU) failed because mount couldn't
> find a valid ext3 filesystem.  Eventually I found a valid superblock,
> but virtually all the files ended up in lost+found.
>
> Steven Timm wrote:
> > Darren--can you temporarily stop the xen guest and mount
> > its root FS from dom0? if so, then just zero out the root passwd
> > and shadow entry from there, unmount the client rootfs, being
> > sure to fsck it afterwards, then start up the client again.
> >
> > Steve
> >
> >
> > On Tue, 30 Oct 2007, Darren Jacobs wrote:
> >
> > > Hi All,
> > >
> > > I need to get into a xenguest running linux for which the root
> > > password has been lost.  I'm running xen 3.0.3 under RH 5.
> > >
> > > I'm trying to figure out how to get pygrub for this guest to load up
> > > the typical "init=/bin/sh" to get the console to come up at the
> > > command line prompt so I can reset the root password.
> > >
> > > Trolling though google I've see suggestions to add args =
> > > 'init=/bin/sh' or opts = 'init=/bin/sh' to the guest configuration
> > > file.  None of them appeared to have worked.  If I do a 'xen create
> > > echo11 -n' after making any of the above file mods I see that the
> > > args were not modified:
> > >
> > > --
> > > (vm
> > >   (name echo11)
> > >   (memory 500)
> > >   (on_reboot restart)
> > >   (on_crash restart)
> > >   (vcpus 1)
> > >   (uuid cb855323-2867-b84a-d766-32a39d252bb7)
> > >   (bootloader /usr/bin/pygrub)
> > >   (image
> > >       (linux
> > >           (ramdisk /var/lib/xen/initrd.kIQYUw)
> > >           (kernel /var/lib/xen/vmlinuz.Xwl81-)
> > >           (args 'ro root=/dev/VolGroup00/LogVol00')
> > >       )
> > >   )
> > >   (device
> > >       (tap (uname tap:aio:/var/lib/xen/images/echo11) (dev xvda)
> > > (mode w))
> > >   )
> > >   (device (vif (bridge xenbr0) (mac 00:16:3e:69:69:90)))
> > > --
> > >
> > > So I tried to bring the guest up manually from dom0 with " pygrub
> > > /var/lib/xen/images/echo11.dsk".  When the menu comes up I edit the
> > > kernel line directly and insert "init=/bin/sh".  You can see below
> > > that the init statement was indeed read:
> > >
> > > --
> > > [root@dom0 xen]# pygrub /var/lib/xen/images/echo11
> > > Going to boot Fedora (2.6.20-2925.13.fc7xen)
> > > kernel: /vmlinuz-2.6.20-2925.13.fc7xen
> > > initrd: /initrd-2.6.20-2925.13.fc7xen.img
> > > linux (kernel /var/lib/xen/vmlinuz.pBqWti)(ramdisk
> > > /var/lib/xen/initrd.9IdU7X)(args 'ro root=/dev/VolGroup00/LogVol00
> > > init=/bin/bash')
> > > [root@dom0 xen]#
> > > --
> > >
> > > However the guest did not start up :'(  Its starts just fine if I
> > > issue a "xm create echo11".  Any suggestions on where to look from here?
--
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
timm@xxxxxxxx  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.

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