Re: creating a linux domU

[Dima Veselov <kab00m%lich.phys.spbu.ru@localhost>]

On Sat, Jun 27, 2020 at 05:58:53PM +0100, Iain Hibbert wrote:
> So my next step is, trying to create a linux domU (I have NetBSD dom0 and
> domU just fine). This is apparently not so easy and I haven't found the
> right answer in any wiki tutorials or guide. This is where I'm at
>
> I have halted and removed the iso from the disk spec, but it still boots
> into the installer. I guess thats in initrd.gz. I can open a shell from
> the installer and poke around in there but no way to get out that I can
> see. The only disk partition I can mount is an EFI partition which doesn't
> offer much.

You have to get both installed kernel and initrd from your disk image.
In every linux installation you should always make separate /boot of
ext2fs type so you can always work with /boot outside the VM.

If you won't reinstall Linux you can boot into installation image, load
any shell, mount / or /boot and copy installed kernel somewhere via
network.

> I have removed the ramdisk spec but the kernel panics because it can't
> find a rootfs. I guess that must be normal?

It is okay. Kernel and initrd are always paired.

> I can't find any other kernel or ramdisk; surely there would be something
> installed on the disk image I think, but can I get into that from NetBSD
> as it is ext4?  Have tried fuse-ext2 and e2fsprogs with no luck.

As far as I know there is no straight way to get images from ext4 in NetBSD.
But you have options - load installer and run shell, or run VM in HVM mode,
or you can try any live linux with network to copy both kernel and initrd
from /boot of installed system.

> I thought I might be able to install or boot as HVM by adding type = "hvm"
> but I just don't understand the error messages. First, I get
>  HVM direct kernel boot is not supported by qemu-xen-traditional

HVM boots as a regular BIOS computer so you have to remove any PV params
from config.

> so I comment out the kernel line and then I get
>
>  direct boot parameters specified but kernel missing

Try to remove "kernel", "ramdisk" and "extra" parameters from config.

> If I instead try to add bootloader = "pygrub" then I get a different
> error, which is
>
>  Unable to find partition containing kernel
>
> (though I note that the guide/wiki says pygrub is known to be problematic)

In fact it works pretty well on straightforward configuration and it will
if you will make separate /boot of ext2fs type and no LVM. Not sure about
EFI, but it seems to work too.

> Apparently pvgrub is now merged into normal grub but is not enabled in
> pkgsrc, is there a known way to build that?

I have some days spent on it with no success even on Linux.

> I've read that recent linux doesn't seem to work on NetBSD but I've tried
> Centos 6.10 and not really any different. I didn't find a download link
> for an older debian.

--
Sincerely yours,
Dima Veselov
Physics R&D Establishment of Saint-Petersburg University