Adding 64-bit libs for Skype rendered Lenovo G50 laptop unbootable

[Silas S. Brown]

I used a standard Lubuntu 18.04 LTS i386-destkop live CD to install on a Lenovo G50 laptop, the install went well and booted into the new system nicely, but then I remembered this user might want Skype, so I downloaded the Skype deb and found it was amd64-only. The laptop was 64-bit capable but I had only brought an i386 CD.

So I did a "dpkg --add-architecture amd64" and an "apt-get update" and "apt-get install linux-image-generic:amd64" (and reboot) and then tried to apt-get the libraries that dpkg was complaining about when I'd tried to install the Skype deb. This caused apt-get to cascade into changing half the system to amd64 and I had to do "apt-get -f install" a few times, one of which told me I was about to remove essential packages, which I thought was OK because it was going to replace them with the amd64 versions. But it turned out the replacement process involved removing all old packages before installing all new ones, which is not so good when one of those packages is dpkg itself: I ended up with the "cannot exec dpkg" error. So I manually replaced dpkg (using "ar" and "tar" to extract the deb) and carried on (and it reinstalled dpkg from amd64 over the top of my manual replacement), and then I thought everything was OK, but I was getting a few "timeout" and "dpkg unexpected number of operations" errors (sorry I don't recall the exact wording), and then when I rebooted I found the initrd was in an inconsistent state and the system couldn't boot. (Editing the GRUB command to boot single-user and without the "splash" or "quiet" options showed it didn't get any further than initrd-unpack.)

Worse, I couldn't even boot off the CD again, because the Lenovo G50 folks put the CD-booting code on the hard disk. If you elect to replace the existing Windows 8 system with Linux (wiping the hard disk and installing afresh), as I had, the laptop ends up not being able to give you the option to boot a CD-ROM or USB stick, because the menu to do that lived on the hard disk and was wiped by the Linux install. I tried going into GRUB's command mode (hold Shift on boot and then press C in GRUB), but GRUB's "ls" could not see the CD-ROM drive.

Thankfully GRUB could still see USB media, so I took the laptop home and used UNetbootin to put a 64-bit Lubuntu image onto a memory card and put in the standard Grub2 commands "insmod chain", "set root=(hd1)", "chainloader +1" and "boot", then copied off the home directory and made a clean reinstall on amd64. So all is well. But I thought a report of what happened might still be useful.

Perhaps this bug is Lubuntu-related (as the main Ubuntu is no longer shipping a 32-bit installer with 18.04, but Lubuntu is). I first tried to report at https://bugs.launchpad.net/lubuntu/+filebug but that form gave me a choice of "LxFind or LxScreenshot" and nothing else. I am therefore filing it as a general Ubuntu bug in the hope that somebody can refile as appropriate.