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Re: [Xen-users] Xen domU cannot boot via PV-GRUB

On Fri, Jan 14, 2011 at 12:09 PM, GNUbie <gnubie@xxxxxxxxx> wrote:
> I'm wondering why it keeps on expecting the xvd* mapping except that
> if the domU config is really expecting for it.

Let me make this reaaaaaaly simple. You were able to captrure boot
log. That's good.
Your previous boot log shows these

[    0.071713] XENBUS: Device with no driver: device/vbd/2050
[    0.071718] XENBUS: Device with no driver: device/vbd/2064
[    0.071722] XENBUS: Device with no driver: device/vbd/2051

whish should roughly mean you have three block devices on that domU.
Do you know what they are? If not, you need to find out (whether from
domU config file, some kind of Amazon EC2 config page, ask Amazon
support, whatever).

You got the following block IDs (you can derive these from 256*major
number + minor number):
sda -> 2048
sda2 -> 2050
sda3 -> 2051
sdb -> 2064

so you do NOT have anything mapped as sda or xvda.
You NEED to know how you currently have it mapped.
You NEED to know what those three block devices that you currently have are.
You NEED to map your current boot device to sda/xvda/hda/whatever
(since you have partitions on it)

Loading xen-blkfront.ko module
[    0.456365] blkfront device/vbd/2050 num-ring-pages 1 nr_ents 32.
[    0.460302] blkfront device/vbd/2064 num-ring-pages 1 nr_ents 32.
[    0.484444] blkfront device/vbd/2051 num-ring-pages 1 nr_ents 32.
[    0.487167] blkfront: regular deviceid=0x802 major,minor=8,2,
assuming parts/disk=16
[    0.488610] blkfront: regular deviceid=0x810 major,minor=8,16,
assuming parts/disk=16
[    0.488850]  xvdb: unknown partition table
[    0.559870] blkfront: regular deviceid=0x803 major,minor=8,3,
assuming parts/disk=16

Those lines show you have xen-blkfront, which is good.
Your kernel uses xvd names instead of sd, which doesn't really matter
as long as you know what it uses.
But you do NOT see partition mapping on the disks, which is bad. You
should see something like this (from my Ubuntu boot log)

[    0.774316] blkfront: xvda: barriers enabled
[    0.775478]  xvda: xvda1 xvda2 xvda3

or something like this (from my RHEL5 boot log)

Loading xenblk.ko module
Registering block device major 3
 hda: hda1
 hdb: hdb1

Perhaps you forgot to build partition support (CONFIG_MSDOS_PARTITION=y)?

In any case:
- find out EXACTLY what your config is like
- map disks the way you want it (e.g map first disk as xvda, NOT
xvda1). Ask Amazon support if you don't know how.
- make sure the necessary kernel support is builtin (partition
support, xen frontend block driver, etc.). If you don't know about
these things simply start with your distro's default kernel.


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