On the other side of cloud

Tags:kernel linux pae xen

I am trying to install xen on my debian a week ago, but failed because of that damn PAE build-in debian kernel for xen and my poor Pentium-M without PAE. Today I retried to install xen(now the version is 3.0.4) from source. Follow the README in the package, everything goes well except extremely long time waiting for kernel compiling - it filled kernel with all kinds of driver modules…

I went with option KERNELS=”linux-2.6-xen0 linux-2.6-xenU” first, everything goes well. But when I try to customize kernel and build a linux-2.6-xen kernel(not only a dom0, but also a an unprivileged guest kernel), and reboot it, I found I encountered this:

VFS: Cannot open root device “hda7″ or unknown-block(0,0)
Please append a correct “root=” boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(0,0) (XEN) Domain 0 crashed: rebooting machine in 5
seconds. (XEN) Domain 0 crashed: rebooting machine in 5 seconds.

I double checked my /boot/grub/menu.lst, and it was written correctly. So I looked it for google, and mailing list of xen-users told me that:

The -xen kernel is built with almost all drivers configured as modules; hence you’ll need an initrd including the driver[s] for your scsi or ide controller so you can mount the root filesystem.

So what I have to do is add a initrd for my xen kernel. But later I found that mkinitrd which mentioned in README is out of date. According to the Debian Wiki, debian have switched from initrd to initramfs. So another tool is introduced. Offical debian kernel package needs initramfs to preload modules that the kernel didn’t build in but as a module(e.g. ext3, ide, input device), just like the case linux-2.6-xen.

It’s easy to get a initramfs with yaird(and also mkinitramfs can be used too, which appears to be more widely used). Yaird’s configure file located at /etc/yarid, but almost nothing need modified in my case. So I only run following command as a sudoer:

yaird –verbose –output=/boot/initrd.img-xen 2.6.16.33-xen

And appended the following line to the xen’s section in /boot/grub/menu.lst:

title Xen 3.0.4 / XenLinux 2.6.16.33
root (hd0,6)
kernel /boot/xen-3.0.gz
module /boot/vmlinuz-2.6.16-xen root=/dev/hda7 ro console=tty0
module /boot/initrd.img-xen

Take care of “module”. It isn’t “initrd”, for xen take over the kernel while booting.

And reboot, everything goes well with your customize kernel.

Tags:debian kernel pae xen

Recently I bought a two-hand T41 with Pentium-M 1.6G. Today I am trying to install xen on my debian (etch). But I am failed by following the regular step on debianwiki, for the reason that pentium-m didn’t support PAE which used to manage >4G memories. I think I don’t have so many memories, so I want to install a xen without pae (and I noticed that it’s curious apt installed package with pae by default), which is package “xen-hypervisor-3.0.3-1-i386″. And kernel package is “linux-image-2.6.18-4-xen-686 “. But I still failed after reboot. It reports that “PAE mode mismatch between Xen and DOM0 (xen=no, dom0=yes)” and reboot in 5 seconds. I tried to find out another kernel package with xen patched and non-PAE support, but found there is no such kind of thing…

Finally I found a bug report for Debian Kernel Team: another Pentium-M user complain about can’t install kernel package with xen. But the bug was tagged “won’t fix”… And the developer said that the xen patch was unstable when using with a non-pae support machine, and it was only appear in some of Pentium-M cores.

God….

UPDATE: I have installed xen from source successful, and everything goes well.