Re: [Xen-users] Xen 4.0 Custom kernels

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, May 13, 2010 at 07:40:51PM -0300, Net Warrior wrote:
> Hi there guys
> 
> As a test, I started using the same kernel and initramfs like in Dom0
> which i know it works, but when starting up DomU I've get.
> 
> switchroot: mount failed: No such file or directory
> Kernel panic - not syncing: Attempted to kill init!
> Pid: 1, comm: init Not tainted 2.6.31.13 #14
> 

So the dom0 initrd image is not suitable for domU, ie. it doesn't load 
xen block frontend driver.. most probably. So the domU kernel is
not able to access the virtual disks provided to it.

> I've got the same error while setting up Dom0 and was a problem with
> the scsi modules which I included in the kernel and not in the
> initramfs, my bad !!
> 
> My config file looks this.
> #----------------------------------------------------------------------------
> # Kernel image file.
> kernel = "/boot/vmlinuz-2.6.31.13"
> 
> # Optional ramdisk.
> ramdisk = "/boot/initrd-2.6.31.13.img"
> 
> disk = [ 'phy:VG-NW/root,sda1,w','phy:VG-NW/swap,sda2,w' ]
> 

You should use xvda1 and xvda2 here, not sda1 and sda2.
the sd* naming is deprecated for xen PV guests.

> Also copied the /lib/modules/kernel_version to the *guest* partition.
> 
> What am I missing?
> 

You need to create an initrd image that is suitable for the domU.

Also did you specify root= parameter for the domU kernel?

-- Pasi

> Thanks for your time and support
> Regards
> 
> 
> 
> 
> 
> 
> 
> 
> 2010/5/13, Pasi Kärkkäinen <pasik@xxxxxx>:
> > On Thu, May 13, 2010 at 02:38:40PM -0300, Net Warrior wrote:
> >> Hi Pasi.
> >>
> >> Did not know I could use the Vanila Kernel for DomU usage, I thought
> >> it has to be patched somehow as well.. so good news, I'll try to
> >> compile a custom one using the latest stable from kernel.org and leave
> >> the Dom0 which is working as it is.
> >>
> >
> > I recommend using the latest stable 2.6.32.x kernel for the domU.
> >
> > If you're building a 32bit domU kernel remember it needs to be PAE (64G mem
> > support),
> > otherwise you won't see the pvops Xen domU options at all in the kernel
> > configuration.
> >
> > There are no special requirements for 64bit domU kernel.
> >
> > -- Pasi
> >
> >> Thanks for your time and support
> >> Regards
> >>
> >>
> >>
> >>
> >>
> >> 2010/5/13, Pasi Kärkkäinen <pasik@xxxxxx>:
> >> > On Thu, May 13, 2010 at 12:38:00PM -0300, Net Warrior wrote:
> >> >>    Hi there guys.
> >> >>
> >> >>    I'm using CentOS 5.4, I was able to compile my custom Dom0 kernel
> >> >> and
> >> >> boot
> >> >>    it, now I've got some doubts.
> >> >>
> >> >>    I'd like to compile a custom DomU image, the problem is that when I
> >> >> do,
> >> >>    make kernels KERNELS="linux-2.6-xen0 linux-2.6-xenU" it tries to
> >> >> download
> >> >>    the kernel
> >> >>    from the HG repository which seems to have old 2.6.18 kernels, I
> >> >> want
> >> >> to
> >> >>    use the GIT repository which is alrealdy downloaded and is the
> >> >> source I
> >> >>    used to complile Dom0 using
> >> >>    kernel 2.6.33.13.
> >> >>
> >> >
> >> > specifying KERNELS="linux-2.6-xen0 linux-2.6-xenU" will compile
> >> > linux-2.6.18-xen,
> >> > that's how it should be.
> >> >
> >> > If you don't specify KERNELS= at all, then it'll build linux-2.6.31.x
> >> > kernel.
> >> > Or alternatively you can specify KERNELS="linux-2.6-pvops" to get the
> >> > same
> >> > result.
> >> >
> >> >>    Question:
> >> >>    Which files do I have to modify or how do I have to proceed to
> >> >> achieve
> >> >>    what I want?
> >> >>
> >> >
> >> > Did you know you can use the *default* (vanilla) kernel.org Linux
> >> > kernels as
> >> > Xen PV domU?
> >> > No patches needed for that, the upstream kernels will work for domU.
> >> >
> >> >>    Under /usr/src/xen-4.0.0/buildconfigs I can see some files which
> >> >> define
> >> >>    some stuff depending on what I chose but not sure if it's safe to
> >> >> mees
> >> >>    with this.
> >> >>
> >> >>    Thanks for your time and support.
> >> >
> >> > Hopefully that helps.
> >> >
> >> > -- Pasi
> >> >
> >> >
> >

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