Comment 6 for bug 1523637

I just installed thrice; installed 16.10 on mpath0 and then mpath1; and finally installed 14.04 on mpath0. I was expecting to reproduce this bug by seeing mpath1 being wiped after being detected as the PReP bootdev, but it was not.

Could you please run '/usr/lib/grub-installer/prep-bootdev -l' on the system just before grub-installer runs?

The major problem is that we shouldn't see /dev/sda picked at all, since it's not the device that was selected for the install, and we see that grub-installer already knows it should try to match a partition to /dev/sdb in your logs:

Jan 14 22:16:41 main-menu[1409]: (process:72206): /usr/lib/grub-installer/prep-bootdev
Jan 14 22:16:41 main-menu[1409]: (process:72206): +
Jan 14 22:16:41 main-menu[1409]: (process:72206): wipe_bootdev=/dev/sda1
Jan 14 22:16:41 main-menu[1409]: (process:72206):
Jan 14 22:16:41 main-menu[1409]: (process:72206): +
Jan 14 22:16:41 main-menu[1409]: (process:72206): /usr/lib/grub-installer/prep-bootdev
Jan 14 22:16:41 main-menu[1409]: (process:72206): -l
Jan 14 22:16:41 main-menu[1409]: (process:72206):
Jan 14 22:16:41 main-menu[1409]: (process:72206): +
Jan 14 22:16:41 main-menu[1409]: (process:72206): [
Jan 14 22:16:41 main-menu[1409]: (process:72206): /dev/sda
Jan 14 22:16:41 main-menu[1409]: (process:72206): =
Jan 14 22:16:41 main-menu[1409]: (process:72206): /dev/sdb
Jan 14 22:16:41 main-menu[1409]: (process:72206): ]

There's still the issue of checking for the existence of the device node before running dd, to avoid crashes.