Computer won't boot after installation of Ubuntu

This is not a compiz issue.

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.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1503217/+editstatus and add the package name in the text box next to the word Package.

Solution:

2. Some computers, after a seemingly flawless installation of Ubuntu or Mint, won't boot. I'll describe two situations here.

a. You see the following error, in white letters on a black screen:

error: unknown filesystem
grub rescue>

In that case you've probably used an USB memory stick for the installation (Live USB). It happens sometimes, that the memory stick identifies itself as sda and the hard disk as sdb. And that's how it configures bootloader Grub then, during the installation!

After the installation bootloader Grub wants to boot from sdb, but sdb has disappeared: the hard disk should be addressed as sda now. The installer has therefore correctly installed and configured everything for sda, except for.... Grub.

In that case it suffices to redirect Grub to sda, which you can do as follows. The easiest method is when you use an Ubuntu or Mint DVD for that, because then you can be sure that there will be no new switching of sda into sdb in the live session.

When you don't have the option to use a DVD, then you might try a Live USB of Xubuntu 14.04 LTS, because that one probably has no switching problem (at least in my limited experience).

b. In another situation you may see one of these two errors, in white letters on a black screen:

error: invalid arch independent ELF magic.
grub rescue>

Or this error:

error: file '/boot/grub/i386-pc/normal.mod' not found.
grub rescue>

In that case the cause may be, that Ubuntu or Mint has installed a wrong kind of boot loader. Namely Grub for EFI / UEFI (grub-efi) instead of the ordinary Grub for BIOS.

Among others, this happens on a Lenovo B570e laptop. Although this computer has a UEFI and not a BIOS, this UEFI has been configured by Lenovo to behave as if it were a BIOS. That's why it needs the ordinary Grub for BIOS.

Reparation is then pretty simple: install the ordinary Grub with the Ubuntu or Mint DVD.