Xen users - Apr 2009 - how to boot domU XEN guest in safe mode?

Hi all,

How can I boot a XEN domU guest into safe mode? One of our servers was
forcefully shutdown, and it seems like one of my VM''s could be
corrupt, or something.


When I boot it up, I get the following on the console:

Creating root device.
Mounting root filesystem.
kjournald starting.  Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
Setting up other filesystems.
Setting up new root fs
no fstab.sys, mounting internal defaults
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
/sbin/init: error while loading shared libraries: libselinux.so.1:
cannot open shared object file: No such file or directory
Kernel panic - not syncing: Attempted to kill init!



So, is it possible to boot the VM into safe mode, and fix this problem somehow?

-- 

Kind Regards
Rudi Ahlers

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Rudi Ahlers wrote:
> So, is it possible to boot the VM into safe mode, and fix this problem
somehow?
This has nothing todo with a safe mode, just mount the filesystem 
somewhere else and fix the corrupted files.


Stefan


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On Sun, Apr 5, 2009 at 4:49 PM, Stefan de Konink <stefan@konink.de>
wrote:
> Rudi Ahlers wrote:
>>
>> So, is it possible to boot the VM into safe mode, and fix this problem
>> somehow?
>
> This has nothing todo with a safe mode, just mount the filesystem somewhere
> else and fix the corrupted files.
>
>
> Stefan
>
>
> _______________________________________________

Hi Stefan,

Are you saying, I should mount the LVM on the host node, and then run
fsck on the mounted LVM, or are you referring to something else?



-- 

Kind Regards
Rudi Ahlers

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Rudi Ahlers wrote:
> Are you saying, I should mount the LVM on the host node, and then run
> fsck on the mounted LVM, or are you referring to something else?
You should fsck first and then mount; (to see if that library still exists)


Stefan

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On Sun, Apr 5, 2009 at 5:06 PM, Stefan de Konink <stefan@konink.de>
wrote:
> Rudi Ahlers wrote:
>>
>> Are you saying, I should mount the LVM on the host node, and then run
>> fsck on the mounted LVM, or are you referring to something else?
>
> You should fsck first and then mount; (to see if that library still exists)
>
>
> Stefan
>
> _______________________________________________
Ok, after running fsck, and trying to boot the VM again, I still get
the same error.

Can I just copy that library from the internet somewhere, since I
won''t be able to yum update, or anything like that?

-- 

Kind Regards
Rudi Ahlers

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On Sun, Apr 5, 2009 at 9:23 PM, Rudi Ahlers <rudiahlers@gmail.com>
wrote:
> Hi all,
>
> How can I boot a XEN domU guest into safe mode?
When using pygrub, start the guest with "xm create -c" or "xm
start
-c", and you can edit the grub menu to add "single".

If the domU is using kernel and initrd from dom0, you should be able
to add "extra=single" on domU config file.
> /sbin/init: error while loading shared libraries: libselinux.so.1:
> cannot open shared object file: No such file or directory
> Kernel panic - not syncing: Attempted to kill init!
As Stefan said, it might be easier to check for the missing file by
fsck and mounting domU''s filesystem from dom0. Be sure to do this ONLY
while domU is stopped though. If it was indeed missing, then most
likely you''re experiencing a serious problem and the missing file is
just the tip of the iceberg. I highly suggest you call a Linux expert
to help fix the problem.

If you insist on restoring the file manually, you need to know :
- which packages were damaged, what version (something like "rpm -V"
and "rpm -qa" on chroot or single mode)
- get the original package.
- extract it and copy the missing package
If you don''t know how to perform the above steps, it would be easier
to simply create a new domU and copy data from the old one.

Regards,

Fajar

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On Sun, Apr 5, 2009 at 5:21 PM, Fajar A. Nugraha <fajar@fajar.net>
wrote:
> On Sun, Apr 5, 2009 at 9:23 PM, Rudi Ahlers <rudiahlers@gmail.com>
wrote:
>> Hi all,
>>
>> How can I boot a XEN domU guest into safe mode?
>
> When using pygrub, start the guest with "xm create -c" or
"xm start
> -c", and you can edit the grub menu to add "single".
>
> If the domU is using kernel and initrd from dom0, you should be able
> to add "extra=single" on domU config file.
>
>> /sbin/init: error while loading shared libraries: libselinux.so.1:
>> cannot open shared object file: No such file or directory
>> Kernel panic - not syncing: Attempted to kill init!
>
> As Stefan said, it might be easier to check for the missing file by
> fsck and mounting domU''s filesystem from dom0. Be sure to do this
ONLY
> while domU is stopped though. If it was indeed missing, then most
> likely you''re experiencing a serious problem and the missing file
is
> just the tip of the iceberg. I highly suggest you call a Linux expert
> to help fix the problem.
>
> If you insist on restoring the file manually, you need to know :
> - which packages were damaged, what version (something like "rpm
-V"
> and "rpm -qa" on chroot or single mode)
> - get the original package.
> - extract it and copy the missing package
> If you don''t know how to perform the above steps, it would be
easier
> to simply create a new domU and copy data from the old one.
>
> Regards,
>
> Fajar
>
Hi Fajar,

Thanx for the tip, but unfortunately the VPS was beyond repair, and I
had to recreate it from scratch.

-- 

Kind Regards
Rudi Ahlers

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On Mon, Apr 6, 2009 at 12:12 PM, Rudi Ahlers <rudiahlers@gmail.com>
wrote:
> Hi Fajar,
>
> Thanx for the tip, but unfortunately the VPS was beyond repair, and I
> had to recreate it from scratch.
Sorry to hear that. Is the domU using storage-backed files, with
"file:/" in domU config ?

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On Mon, Apr 6, 2009 at 8:06 AM, Fajar A. Nugraha <fajar@fajar.net>
wrote:
> On Mon, Apr 6, 2009 at 12:12 PM, Rudi Ahlers <rudiahlers@gmail.com>
wrote:
>> Hi Fajar,
>>
>> Thanx for the tip, but unfortunately the VPS was beyond repair, and I
>> had to recreate it from scratch.
>
> Sorry to hear that. Is the domU using storage-backed files, with
> "file:/" in domU config ?
>
> _______________________________________________

Hi Fajar,

No, it''s using an LVM partition:


root@usaxen01:[~]$ more /home/xen/knocky.vm/knocky.vm.cfg
kernel     = ''/boot/hypervm-xen-vmlinuz''
ramdisk    = ''/boot/hypervm-xen-initrd.img''
memory     = 1024
name       = ''knocky.vm''
disk       = [''phy:/dev/VolGroup01/knocky_rootimg,sda1,w'',
''phy:/dev/VolGroup01/
knocky_vmswap,sda2,w'']
root = ''/dev/sda1 ro''




-- 

Kind Regards
Rudi Ahlers

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