In the beginning I had Debian 6 running on one hard drive (/dev/sda1). Then I decided to keep all my stuff(pics, videos, etc..) in another slave hard drive (/dev/sdb1).

So sda1 has Debian OS sdb1 doesn't contain any OS files

I have made it to mount automatically by adding a row in /etc/fstab (UUID and directory to mount to)

Time have passed and when I tried to change that secondary hard drive with another hard drive with bigger capacity, for some reason Debian won't boot (just itself sda1) after removing secondary hard drive (sdb1)

But if I plug sdb1 back, it boots just fine.

I tried to comment line out from /etc/fstab, so it doesn't mount And also did update-grub after umount /dev/sdb1

What's the right way to remove hard drive secondary hard drive?