How to resize /home partition in Ubuntu Gutsy Gibbon (7.10)

My new system has a partition dedicated to /home (which quite a common practice, I think) but unfortunatly I made it too big during the installation so that now I need to resize it.

Can't use GParted

I installed the Gparted package via Synaptic but Gparted can not resize a mounted partition. I don't know if it is possible to unmount the partiton of /home and still be running a shell as anything but root.

Since Ubuntu doesn't allow logging in as root (I think) and that I didn't want to risk anything, I found another way: the installation CD.
That will be the alternate CD in my case because I've got a 8800GT not supported by the liveCD.

Using the alternate installation CD

Insert the CD in the CD drive and reboot. When prompted, choose "repare broken installation" (or something like that).

The text installation starts as would a fresh installation start. It detects the network, asks for a machine name.
When you get at the point where the installation asks which device to mount on "/", stop and clic the "cancel" or "back" button.
You should be getting to the screen where you can choose to got to a specific step of the installation process (it's a long list). Select the one for the partition tool.
Once the tool has detected the drives, select the one partition mounted to "/home".
On the new screen, you see details of the selected partition and several possible actions at the bottom (among which there is the quit this screen option), select the "resize this partition" option.
On the new screen, indicate the new size of the partition. And "click" the "ok" button and let the tool resize your partition !
Once you get back to the partition detail screen, select the "quit this screen" action.
If you don't want to create a partition for the now available disk space, click the "cancel/back" button and do it using Gparted after the reboot.
You should be back on the screen where you can choose a specific step of the installation, select the "quit/cancel installation" (at the bottom) option. You can now reboot, that's it.