And actually this is a very recent regression. In the live env I downgraded grub-common and grub-pc to 1.99~20110104-2ubuntu1 and the probe command returns correctly:
#grub-probe --verbose --target=device /cdrom/boot/grub /dev/sda2 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/700910 Title: Unable to install GRUB2 to the same device as contains aufs in natty -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
