The other day, I was helping my brother install Ubuntu on his brand new laptop (Lenovo ideapad). Since I’ve installed linux for the first time things have improved quite a bit (that was on a pentium 75 after printing 100 of pages of documentation as at that time, I had only one computer and no Internet). So I wasn’t expecting any surprises.
However after starting the ubuntu 12.04 installer from the live usb and diving into the installation: no partition were detected at all. Nothing, just a blank menu and no other choice. And if you try to go on with the installation: “No root file system is defined”. I couldn’t find much about that after some fair amount of googling around. The Wubi installer would run into the same problem.
Gparted was working fine and had no problem seeing and changing the partition, but the installer would stubbornly refuse to see anything.
Unrelated rant: I really don’t understand how Lenovo had the brilliant idea to ship laptops with 4 primary partitions (boot, windows and 2 ‘lenovo’). To install anything else, no other choice than bursting one of the lenovo partition to create a logical partition…
It appeared that the laptop is configured with a small SSD mounted in RAID with the hard disk (my guess is this is to improve the performances of the hd). And Ubuntu is setup to ignore any disk that is part of a raid array (to avoid breaking an array, I guess).
One way to confirm if your issue is similar to mine
sudo mdadm --examine /dev/sdb
should show something like intel raid ism cfg sig.
So after identifying the issue, the solution was pretty simple (it took more time to double check that this would not break things around).
After starting Ubuntu from the live usb:
sudo apt-get install mdadm sudo mdadm --zero-superblock /dev/sdb
Then, go ahead with the installation.
After that, during the next startup the bios detect the incomplete array and ask you what you want to do. At that point, I just removed the SSD from the raid (it was getting late), but it’s probably worth trying to add the hd back to the array now that the install is done.