Ubiquity switches sda and sdb in Grub configuration, causing boot failure

Bug #1070485 reported by Pjotr12345 on 2012-10-23
This bug affects 5 people
Affects Status Importance Assigned to Milestone
ubiquity (Ubuntu)

Bug Description

When I install *buntu 12.10 by means of a Live USB (USB memory stick), Ubiquity often (not always) wrongly identifies the memory stick as 'sda' and the hard disk as 'sdb'.

Ubiquity then installs *buntu 12.10 nevertheless on the hard disk with nearly all configuration right, namely the hard disk as 'sda'. With one fatal exception: Grub. Grub is configured to boot from 'sdb'.

Upon first boot from the hard disk (with the USB stick removed), Grub then of course spawns this error:
error: unknown filesystem
grub rescue>

When I found out what the cause was, it was easy to repair: simply boot up the PC by means of a *DVD* and point Grub to 'sda' by means of this terminal command:
sudo mount /dev/sdaX /mnt && sudo grub-install /dev/sda --root-directory=/mnt
(where the X in sdaX needs to be replaced by the partition number of the root partition)

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in ubiquity (Ubuntu):
status: New → Confirmed
Timo (timo.diedering) wrote :

This bug doesn't pop up at all systems: My laptop for example is affected by this bug, but if I install Ubuntu (with a USB stick of course) on my desktop, it just boots...

Heimen Stoffels (vistaus) wrote :

The problem happened here too. On my Thinkpad E525 everything went just fine but on my Thinkpad E535 the bug did occur.

Adam Conrad (adconrad) wrote :

I assume this only happens on systems where the BIOS decides to re-map the boot device (ie: the USB stick, when installing) to INT 80.

Pjotr12345 (computertip) wrote :

@ Adam Conrad: how can I check this?

Note: the laptop it happens on in my case, is a fairly new Lenovo b570e.

Adam Conrad (adconrad) wrote :

Actually, a bit of reading suggests that remapping the boot drive (even a USB stick) to 80H is the right thing to do anyway, so is probably the behaviour of most BIOSes, and probably not the cause of this bug. I'll leave it to others to debug more formally at some point, though.

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