Re: A bit off topic.. converting Linux HVM to PV

[Brian <brian%planetunix.net@localhost>]

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If you installed Linux as an HVM, it's more than likely that your file
system image includes an MBR and other artifacts like that.  You need to
adjust your Xen config file.  Use 'xvda' instead of 0x301.

For instance:

disk = [ 'file:/path/to/image,xvda,w' ]
root = "/dev/xvda1 ro"

As far as I know, Linux will not attempt to look for partitions inside
/dev/xvda1 if it is supplied as such in the Xen config.

I have done several HVM to PV installs recently while trying to build a
Xen image library of different Linux distributions that I intend on
providing to the public, ala stacklet.

Sincerely,
Brian Brombacher
PlanetUnix Networks

Brad Spencer wrote:
>    On 07.10.2010 22:39, Brad Spencer wrote:
>    >>> I think I managed to build a Linux kernel with Xen guest support.  It
>    >>> claims the following upon trying to 'xm create -c ...':
>    >>
>    >> How did you create it?
>    > 
>    > Probably badly...  basically...
>    > 
>    > cd /usr/src/linux
>    > make menuconfig
>    > Select all of the Xen guest packages and bits and exit
>    > make clean
>    > make vmlinux
>    > 
>    > After the build, copy vmlinux to the place I hold PV kernels and try to
>    > use it.
>    > 
>    >> Was it configured to use a ramdisk? What fs are compiled in/modularized?
>    > 
>    > I have to admit I don't know how to tell if it is using a ramdisk??  For
>    > fs support, at first it just had romfs, but I did edit .config and added
>    > all of the ext-foo filesystems and rebuilt.  Didn't help.
> 
>    There's a wiki page on XenSource if you want to build from the git repo.
> 
>    http://wiki.xensource.com/xenwiki/XenParavirtOps
> 
>    For ramdisk (initrd), see the dom0 build commands at the end of the
>    page. You pass the rd as an option in the domU configuration file:
> 
>    kernel = "/boot/vmlinux-2.6.31-domU"
>    ramdisk = "/boot/initrd.gz"
> 
>    -- 
>    Jean-Yves Migeon
>    jeanyves.migeon%free.fr@localhost
> 
> 
> Thanks.  That was all quite helpful, but I was still unable to get a fully
> PV Linux working.  I did get a ramdisk built with that I thought was
> needed, but I end up with this:
> 
> .
> .
> NET: Registered protocol family 17
> registered taskstats version 1
> XENBUS: Device with no driver: device/console/0
> Freeing unused kernel memory: 672k freed
> Write protecting the kernel read-only data: 8192k
> Freeing unused kernel memory: 996k freed
> Freeing unused kernel memory: 388k freed
> mount: mounting /dev/xvda1 on /mnt failed: Invalid argument
> ERROR:  No /sbin/init found on rootdev (or not mounted).  Trouble ahead.
>         You can try to fix it. Type 'exit' when things are done.
> #
> 
> Something is obviously not included in the RD image and/or kernel I am
> booting.  Although, I have tried building kernels with the supported
> filesystems and have tried making RD images with the supported modules.
> Although it is pretty hard to tell if you have succeeded in ever doing
> that.  The odd thing is that 'od -c /dev/xvda1' does return pages and
> pages of stuff at the above prompt, so it would seem like the device is
> attached.  However, 'mount -t ext4 /dev/xvda1 /mnt' returns an error
> simular to the one above, although ext4 should be available as a usable
> FS, either built in or as a module [depending on which kernel I used].
> 
> This will have to be put on the back burner for now.  Simply no more time
> to work on this.  NetBSD is soo much simpler about all of this.....
> 
> 
> Thanks for your all of your help.
> 
> 
> 
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