So I have wasted spent a few hours on getting Ubuntu14.04 LTS installed on a Windows multi-boot system using the Wubi installer, and encountered a few issues along the way. I could solve all of them, but it required some research. Hopefully, I can save some of you this time.
1 - Getting Wubi
The Ubuntu downlod page does not link to the Windows Ubuntu installer ("Wubi") since a few versions. It's a very convenient tool in making Ubuntu easy to install from Windows, and also to remove it later. However the system does have issues with Windows 8+ systems (UEFI—nuff said). However I had a Windows 7 system where I wanted to boot into Ubuntu, so Wubi sounded like a good idea. There is no separate download, but the ISO of the desktop version of Ubuntu does contain wubi.exe, which is the installer. Just extract this file from the ISO, and run it directly. After setting some options, the system will reboot directly into the Ubuntu installer.
2 - Mounting / and /tmp
Now when installation has completed, the Windows boot loaded will have an entry for Ubuntu. At least in my case, booting into the OS did not work, but showed this frightening error message instead:
Serious errors were found while checking the disk drive for /.
There were three options:
press [I] to ignore, press [S] to skip mounting and press [M] to mount manually.
Ignoring this did not really work, since the next error message mentioned that /tmp could not be mounted. What the eff?!
I eventually found this SO article with several solutions. The most straight forward one was to press e in the Ubuntu boot menu / Grub2 (not the Windows one!). This opens up the boot entry with the associated options. Somewhere in there, there is the actual command that boots up Linux and also mounts the disk— in ro (read-only) mode! Change that to rw, and press Ctrl+X or F10 to resume booting with the changed parameters. And we are in and need to make sure that this change is permanent. For this to happen, I (sudo) edited the /etc/grub.d/10_lupin file and was looking for " ro " (including the blanks, that limited the number of options to 1). I then changed that to rw, saved the file, and updated my Grub2 entries:
Time to be happy! Or maybe not.
3 - Blank Screen
Previous versions of Ubuntu have had their issues with some ATI graphics chips: upon boot, the screen went just blank. Unfortunately, this still seems to be the case with 14.04. I do not want to go into the discussion whether it's Ubuntu's fault or ATI/AMD's. What's important is how to fix that situation. Once again the trick is to open the Linux boot options from the Grub2 window by pressing e. You will find quiet splash somewhere in there. Just prepend or append nomodeset, like this: nomodeset quiet splash. Then, the system should finally boot up. This article on askubuntu.com gives some more details, including pointers on how to make that change permanent. However in my case, running the system updater once I was into Ubuntu was good enough to make reboots work, too.
I my case, I had to do step 3 before step 2. However I hope that other graphics chips do not have this issue, so step 2 should be good enough. Good luck! And yes, I am also flabbergasted that I actually had to do this.