Kubuntu installation into external disk ruins internal disk boot whilst leaving external disk unbootable

[dsainty]

In order to test Kubuntu 14.04.3 LTS desktop hardware support on my laptop I attempted to install it (via USB stick) onto a USB external hard drive, with the plan of booting off the external drive and leaving my internal drive safely alone. I figured I could trust the installer to be sensible.

What a depressingly fatal mistake that was...

The internal drive is now screwed up, it drops to grub rescue if I attempt to boot off it. Manually attempting to use grub rescue seems problematic, because grub rescue doesn't like the licence on the internal drive's grub files.

The external drive can't be booted either, because grub wasn't properly installed on it.

This happened when asking it to do a non-manual install over the entire external drive - including formatting. If I had done a manual install I would have avoided this mess by explicitly asking it to install GRUB on the external drive. Or, if the installer had warned me what it was doing with GRUB, like it does with other file system operations, I might have been able to avoid this mess.

This is obviously a really nasty bug in the installer. If it's asked to install with all normal default actions over entire disk /dev/sdX, it doesn't make sense to do that - except then screw up grub on /dev/sdY.

The explicit process was:

    Where would you like to install Kubuntu: Guided - use entire disk
    Device: SCSI4 (0,0,0) sdc
    <Install Now>

Warning:

    The partition tables of the following devices are changed: SCSI4 (0,0,0) sdc

    The following partitions are going to be formatted:
    partition #1 of SCSI4 (0,0,0) sdc as ext4
    partition #5 of SCSI4 (0,0,0) sdc as swap

NB: Conspicuously absent is any mention that the internal drive (sda) will
never boot again.

This is a repeated pass through the steps for the purposes of reporting the bug. However, I'm pretty sure the first time I did this it ALSO told me it'd format the swap partition on sda. For some reason that is not reported here. Although I wasn't happy it wanted to touch sda, at the same time it seemed relatively harmless, so I let it slide. I mention it just in case it's relevant, though I guess the most likely bug is just poor decision making on where grub is installed.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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[dsainty (dsainty)]

If you encounter the bug when installing Ubuntu from the Desktop CD (most common method), the package is ubiquity.

[Launchpad Janitor (janitor)]

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

[Kelby (kelby.loden)]

Ditto - just ran into this exact same issue attempting to install Kubuntu 16.04 onto an external SSD drive. My internal hard drive had full drive encryption on it and so it was completely trashed and I lost all data on it. Like the guy mentioned in the original post, the whole problem could have been avoided with a simple warning telling me that the guided option will install the boot loader on a different drive than I selected to install Kubuntu on and I should choose the un-guided option to customize that.

[Michael (mdunphy-g)]

I'm writing in to confirm that this problem persists in Kubuntu 16.04.1. I used a bootable Kubuntu usb key to install Kubuntu to an external drive, and the installer trashed my grub configuration on an *unrelated* internal Fedora hard drive.

Workaround in case anybody sees this: unplug any hard drives that you don't want the Kubuntu installer to touch prior to doing your install....