Re: [Xen-users] Can't get template (domU) to work

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Thanks for your help here.  I am still battling this issue but based on the
> details that you have given me, is it safe to assume that I shouldn't be
> using a gentoo domU on a ubuntu dom0 system?

Oh no, mixing different kinds of distros should definitely work.

Although often you *can* get away with booting one distro using another 
distro's kernel the most "authentic" way of booting a guest is to use its own 
preferred kernel / initrd combination.  This was all I was meaning; mixing 
different OS types is definitely intended to work. 

If you can mount the filesystem from the image in dom0 (whilst the guest isn't 
running) then you could have a poke around inside its /boot and see if it has 
a Xenified kernel in there already.  If so, you can just copy that out for 
use.  Or you can try and use pygrub to boot the guest so that you don't have 
to do this (pygrub will access the guest's virtual disk itself in order to 
get a menu.lst / grub.conf and the images it refers to).

Hope that helps.  I've got to go out now so can't write more but if you have 
any questions about this just post back and hopefully somebody will be able 
to cover them (possibly me, later on!).

Cheers,
Mark

> Is it best to be using templates/domU VM's that are based/alike as the dom0
> itself?  For example, if I am running CentOS on my server, I should stick
> with CentOS domU's and nothing else?  And, if I want to run Gentoo domU's,
> then I should build another server running Gentoo to use gentoo domU's?
> Just like now, I have Ubuntu Server running and trying to get gentoo domU
> but not working as stated.
>
> Thanks,
> Tito
>
>
>
> On Sun, Apr 6, 2008 at 3:40 PM, Mark Williamson <
>
> mark.williamson@xxxxxxxxxxxx> wrote:
> > > /etc/xen/gentoo.2007-0.xen3.cfg
> > > /mnt/gentoo/gentoo.2007-0.img
> > > /mnt/gentoo/gentoo.swap
> > >
> > > Here is what my gentoo.2007-0.xen3.cfg looks like:
> > >
> > > root@personal:/etc/xen# cat /etc/xen/gentoo.2007-0.xen3.cfg
> > > kernel = "/boot/vmlinuz-2.6.22-14-xen"
> > > memory = 456
> > > name = "gentoo.2007-0"
> > > vif = [ '' ]
> > > dhcp = "dhcp"
> > > #disk = ['file:/mnt/gentoo/gentoo.2007-0.img,sda1,w',
> > > 'file:/mnt/gentoo/gentoo.swap,sda2,w']
> > > disk = ['tap:aio:/mnt/gentoo/gentoo.2007-0.img,xvda1,w',
> > > 'tap:aio:/mnt/gentoo/gentoo.swap,xvda2,w']
> > > root = "/dev/xvda1 ro"
> > > #initrd = "/boot/initrd.img-2.6.22-14-xen"
> > > extra = "gentoo=nodevfs"
> > >
> > > The problem is that everytime I do:
> > >
> > > root@personal:/etc/xen# xm create gentoo.2007-0.xen3.cfg -c
> > >
> > > I get:
> > >
> > > [ 6195.091118] List of all partitions:
> > > [ 6195.091146] ca01    2049024 xvda1 driver: vbd
> > > [ 6195.091157] ca02      65536 xvda2 driver: vbd
> > > [ 6195.091167] No filesystem could mount root, tried:  cramfs
> > > [ 6195.091179] Kernel panic - not syncing: VFS: Unable to mount root fs
> >
> > on
> >
> > > unknown-block(202,1)
> >
> > It looks like it's trying to mount the root FS, it's trying the only
> > filesystem it can think of (which, apparently, is cramfs), it's failing
> > to mount and then it's giving up.
> >
> > You're not using an initrd - presumably your kernel would normally load
> > the
> > primary filesystem driver from the initrd so that it could mount the root
> > filesystem.
> >
> > I'm not really clear what kernel you're supposed to be using with a
> > jailtime
> > image but I guess you're currently using your Ubuntu kernel?  That might
> > not
> > provide quite such a good Gentoo-like experience as using the Gentoo
> > kernel.
> > Still, lets see if we can get things a bit further at least...
> >
> > > That happens during the boot of the new domU.  I have tried to figure
> >
> > out
> >
> > > if my problem was here in my gentoo*.cfg file:
> > >
> > > #disk = ['file:/mnt/gentoo/gentoo.2007-0.img,sda1,w',
> > > 'file:/mnt/gentoo/gentoo.swap,sda2,w']
> > > disk = ['tap:aio:/mnt/gentoo/gentoo.2007-0.img,xvda1,w',
> > > 'tap:aio:/mnt/gentoo/gentoo.swap,xvda2,w']
> > > root = "/dev/xvda1 ro"
> >
> > That shouldn't be it, although tap:aio might work better in some
> > circumstances.
> >
> > I think you need to get the initrd loading.  On my system the config file
> > uses
> > the "ramdisk=" parameter rather than "initrd=".  Have you tried that?
> >
> > > But I have nooooo luck.  I have looked online everywhere and through
> > > the mailing list to no avail.  Does anyone know why this could be
> > > happening?
> >
> > It's definitely some kind of problem with mounting the root filesystem.
> >  It's
> > fairly common these days for system boot to not work without an initrd,
> > so I
> > guess the packagers might have decided to put the filesystem drivers into
> > that rather than building into the kernel.
> >
> > Hope that helps,
> >
> > Cheers,
> > Mark
> >
> > --
> > Push Me Pull You - Distributed SCM tool (
> > http://www.cl.cam.ac.uk/~maw48/pmpu/<http://www.cl.cam.ac.uk/%7Emaw48/pmp
> >u/> )



-- 
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