Xen installer failed with "cannot install GRUB to harddisk"

[Sven]

I used the files from http://mirror.anl.gov/pub/ubuntu/dists/trusty/main/installer-amd64/20101020ubuntu318/images/netboot/xen/ to install a paraviertualized xen guest.

The Xen configuration file I used is given below. As you can see, the paravirtualized guest sees two disk devices: xvda1 and xvda2. There is no /dev/xvda device, which has an MBR, a partition table, or anything like this.

It was possible for me to tell the installer to put the root filesystem on xvda1 and swap on xvda2. Then, the installation continued all the way till the point when the GRUB bootloader was about to be installed. That failed. I had to chose "continue without bootloader". I assume, it failed since the installer actually tried to install grub to the MBR of /dev/xvda - which doesn't exist.

As the virtual machine uses pygrub, there is point in installing GRUB to some MBR or something. All I want is the grub configuration files for pygrub to pick up.

It seems to me like the xen installer should have an option that only installs the GRUB configuration files but skips the actual installation of GRUB to some boot record or whatever. However, such an option was not in the list. I could only chose between retrying to install GRUB, installing LILO, and continuing without a bootloader.

memory = 7750
vcpus = 8
name = "xen-XXX"

kernel = "/root/ubuntu1404/vmlinuz"
ramdisk = "/root/ubuntu1404/initrd.gz"
extra = "debian-installer/exit/always_halt=true -- console=hvc0"

#bootloader = "pygrub"

disk = [
 "phy:/dev/md4,xvda1,w",
 "phy:/dev/md7,xvda2,w",
]
vif = [
 "bridge=xenbr0,mac=00:50:56:XX:XX:XX",
]

[Ubuntu Foundations Team Bug Bot (crichton)]

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[Sven (sven-koehler)]

I booted the system with a grub.cfg that I created by hand. Then, after installing grub-common, I can run update-grub. The created grub.cfg works. However, update-grub spits out a ton of warnings like described here:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=708614