I’ve just had a shit of a time going from a dual boot setup with Windows on sda and Ubuntu on sdb to a Ubuntu only software RAID1 setup using both drives without having to erase or otherwise screw up the existing Ubuntu install on sdb (I’m using Lucid Lynx).
I finally managed.
The starting point is this tutorial. Problem is, it’s not complete, reading the comments on it saved the day.
1.) First of all the sda drive needed to be formatted and partitioned in an identical fashion to sdb, the easiest way of doing that was running sfdisk -d /dev/sdb | sfdisk /dev/sda. However before this step I used gparted to set set the boot flag on sdb1 ending up with boot on both sda1 and sdb1 in the end. Instead of fooling around with fdisk to set fd on the partitions I used gparted to later set the raid flag on both swap and primaries, much easier and works.
2.) In step #5 the tutorial then instructs you to press e to enter edit mode when the GRUB2 menu shows, I didn’t even get to see the menu… Editing /etc/default/grub and setting the following lines to look like this:
Took care of that problem (that last line has not really got anything to do with this problem but was something I did in the next step).
3.) Finally the whole thing wouldn’t boot up properly, GRUB2 complained that the sector it was trying to boot from didn’t exist and I had to enter insmod normal followed by normal in the grub rescue to get to the menu all the time. Again the comments saved me, doing grub-install –modules=’raid ext2′ /dev/sda and grub-install –modules=’raid ext2′ /dev/sdb followed by update-grub and update-initramfs -u took care of the problem.
Finally it works, does it boot quicker? Maybe a little, however heavy stuff like Eclipse and Firefox seem to start quicker. I’ll update this post as I get a better feeling for things.