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boot problems after upgrading to xen-4.0
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danman
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PostPosted: Tue May 18, 2010 11:40 pm    Post subject: boot problems after upgrading to xen-4.0 Reply with quote

Hi!

The situation is as follows:
1. I have a working dom0, with xen-3.4.2 and 2.6.32-xen-r1 xen-sources kernel.
2. I gave out the "emerge xen" command after I have ssen that xen-4.0 is available.
3. Compilation went fine and I typed in "reboot" (I did nothing else).
4. The boot hangs with this:
[ 62.848947] 0800 1315427328 sda driver: sd
[ 62.849264] 0801 208813 sda1
[ 62.849579] 0802 12594960 sda1
[ 62.849938] 0803 10490445 sda1
[ 62.850254] 0804 1292132047 sda1
[ 62.850569] No filesystem could mount root, tried: ext3 vfat msdos iso9660 ntfs fuseblk udf
[ 62.851466] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,3)
...
5. I booted up the minimal install CD, chrooted in the system and downgraded xen and xen-tools to 3.4.2.
6. After reboot, all was fine again.

Any idea how I can get xen-4.0 up and running? What could be the problem above?

Thank you in advance!

Daniel
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drescherjm
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PostPosted: Wed May 19, 2010 1:58 am    Post subject: Reply with quote

Quote:
[ 62.850569] No filesystem could mount root, tried: ext3 vfat msdos iso9660 ntfs fuseblk udf
[ 62.851466] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,3)


What is your root filesystem? Is it ext3? If not you have not compiled your filesystem into the kernel.
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idella4
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PostPosted: Wed May 19, 2010 4:46 am    Post subject: Reply with quote

That's a little surprising. You emerged a new version of xen, but didn't adjust the booting accordingly, since you did nothing else.

Your bootloader looks something like

root ( )
kernel /boot/xen- xen-3.4.2.gz
module /boot/kernel-2.6.32-xen-r?
module /boot/initrd-2.6.32-...

If you did nothing else, then you're booting into a 3.4.2 hypervisor in system with xen-tools-4 installed. A version conflict.

Perhaps you did change the kernel line to the version 4 and didn't tell us.
I'm still on 3.4.2, not breaking my neck to try 4 just yet. Have no idea if 4. introduced some radical change,
but it's likely it did since it corrected when you reverted.
That said, the boot up fault looks like it's ill-equipped fs wise;
Just try adding

none /proc/xen xenfs defaults 0 0

to fstab; it should create it of its own accord.

Can you confirm your setup?
You can also try installing xen 4 source directly from xensource. It won't hurt gentoo, and you can always re-emerge over the top of it.
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danman
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PostPosted: Wed May 19, 2010 6:41 am    Post subject: Reply with quote

Hi idella4!

Thanks for the reply.

My grub.conf looks as follows with 3.4.2:
title Gentoo Linux 2.6.32-xen-r1_dom0
root (hd0,0)
kernel (hd0,0)/xen.gz dom0_max_vcpus=2 dom0_vcpus_pin dom0_mem=1024m
module (hd0,0)/kernel-2.6.32-xen-r1_dom0 root=/dev/sda3

When I minimalCDd into the xen-4.0 installation's /boot, I saw the symbolic links for xen-4.0, and xen.gz pointed on xen-4.0.0.gz or xen-4.0.gz, thus probably the above boot parameters were valid. Am I missing something?
I don't have initrd, it isn't enabled in the kernel either.

I never had this one in fstab:
none /proc/xen xenfs defaults 0 0
When upgrading to xen-4.0, can this be the solution for the problem, can it help me if I add it?

My fstab looks like this:
# NOTE: If your BOOT partition is ReiserFS, add the notail option to opts.
/dev/sda1 /boot ext3 noauto,noatime 1 2
/dev/sda2 none swap sw 0 0
/dev/sda3 / ext3 noatime 0 1
# Logical volumes
/dev/vg/usr /usr ext3 noatime 0 2
/dev/vg/home /home ext3 noatime 0 2
/dev/vg/opt /opt ext3 noatime 0 2
/dev/vg/var /var ext3 noatime 0 2
/dev/vg/tmp /tmp ext3 noatime 0 2
shm /dev/shm tmpfs nodev,nosuid,noexec 0 0


Testing is not an easy task, because if it breaks, I have to use IPMI to upload a minimal CD with a slow connection, so first I am just trying to get some info ;-) And I am very happy that I was able to revert.

Regards,
Daniel
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idella4
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PostPosted: Wed May 19, 2010 8:18 am    Post subject: Reply with quote

Quote:

I saw the symbolic links for xen-4.0, and xen.gz pointed on xen-4.0.0.gz or xen-4.0.gz,


So that indicates you were booting into xen 4 with xen utils 4. It is unlikely that xen-tools would interfere so early in the boot process.
It's hard to pinpoint with such limited info. You can try a few things;

-- make a few entries in the grub, no need for just one.

e.g. my list has

title genny 2.6.26-gentoo fbsplash-Morphix (on /dev/sda6)
root (hd1,5)
kernel /boot/kernel-2.6.26-gentoo ro real_root=/dev/sda6 video=uvesafb:mtrr:3,ywrap,1024x768-24@60 splash=verbose,theme:Morphix console=tty1
initrd /boot/fbsplash-Morphix-1024x768

title genny 2.6.30-gentoo fbsplash-livecd-2007.0 (on /dev/sda6)
root (hd1,5)
kernel /boot/kernel-2.6.30-gentoo-r8 ro real_real_root=/dev/sda6 video=uvesafb:mtrr:3,ywrap,1024x768-24@60 splash=verbose,theme:livecd-2007.0 console=tty1
initrd /boot/fbsplash-livecd-2007.0-1024x768

It's an old redundant entry. But no need to limit yourself to one version in one state.

Re -emerge xen 4, but adjust your entries, leave links to xen.gz, hard code it

kernel /boot/xen-3.4.2.gz

kernel /boot/xen-4.0.gz

No reason why the two can't co-exist. i.e. ls /boot/

xen-3.4.2.gz
xen-4.0.gz

So the way you did it, at boot, you had only

kernel /boot/xen-4.0.gz

Don't see why you couldn't have the choices at boot of alternate entries into gentoo. By rights, one version should be able to boot into another, ???
Gentoo's xen 4 may be at fault. A previous version missed building key elements, but booted up ok,
If version 4. misfires, have the backup of the reliable 3.4 Just maybe a remnant file or two of 3.4 interfered with xen 4, just maybe.

Try with an initrd, but it shouldn't be required to boot dom0.

As I said, consider installing from xen source and it can compare and contrast. xen is after all quite complex and sometimes delicate.

the fstab entry is something I came across. Just try it, it coincides with your problem.

In time I can try version 4, maybe soon.
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danman
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PostPosted: Wed May 19, 2010 9:35 am    Post subject: Reply with quote

Hi drescherjm!

The kernel can not be a problem here, because with the exact same kernel everything goes fine if I have xen-3.4.2.
BTW it is ext3 of course, but this really isn't the problem, that's for sure! :-)

Hi idella4!

Ok, you are right that I can test probably xen-4 with xen-3.4.2 stuff loaded in /boot. Then I wouldn't need to minimalCD all the time :-)
I think I will wait for newer versions of xen and kernels, and try then. Or maybe try it from source as you have suggested.

Thank you for the help!

Regards,
Daniel
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