Comment 8 for bug 912431

We have this problem too. The fix is in grub-installer in the udeb.

The problem is the grub_probe function in that script. It does an apt-install and then calls grub-probe in the chroot. The apt-install prints output, however, and the callers of grub_probe expect to see only the output from grub-probe itself. As a result, output from apt-install is slammed into the variables which later become the arguments to mapdevfs.

If you do 2>&1 > /dev/null after the apt-install in that function, the install proceeds without a problem.