I have an Acer Aspire One AO751H, and I've got two Ubuntu versions on it: 10.04.4 LTS Netbook Edition (which I keep around mainly because I really like the user interface) and 12.04.2 LTS. I have one primary and one extended partition, the former containing 10.04 alone, and the latter having 12.04 with its 2GB swap partition. My question is: will 10.04 recognize and use the swap space in the extended partition, or do I have to enable that? If so, what is the procedure for doing so? Any help would be much appreciated.
If the 10.04 is already installed, then the answer is no. It will not automatically use the swap partition. You have to manually add the partition to your fstab file. See the following for how to do that:
https://help.ubuntu.com/community/SwapFaq#How_do_I_add_more_swap.3F (section "Activating the swap partition")
If the 10.04 is not installed yet, you can configure it to use the pre-existing swap partition during installation (you have to select the manual partitioning option to do that).
Important: be careful as the current implementation of hibernation (suspend to disk) in Ubuntu uses the swap partition. That means if you hibernate one of the installations it will write the contents of RAM into the swap partition, which may lead to problems if you start the second installation before resuming the first.