In theory, an XFS file system can be enlarged without losing any data.
However, GParted will certainly advise you to backup your data first. So, I
guess things might go wrong. I have never seen such a problem though. Anyway,
I guess you do not have many new data since you backed up them on DVDs.
Extending a partition with GParted is very easy. You just need to remove an
adjacent partition and move a cursor. The space being gained from the root
partition, this is the one to remove. If there is another partition in
between, you either have to remove it as well (if it is a swap partition, for
instance, there is no problem in removing it) or move it at the end of the
free space you gained from the root partition.
Then, you can recreate the deleted partitions either from GParted or relying
on the installer. Anyway, you will have to choose the custom partitioning
during the install so that you can specify the home partition and uncheck the
box specifying whether it should be formatted. Do not forget to uncheck this
box!
An application you want to know about is the Baobab disk analyzer. Trisquel
installs it by default (you can find it in the menu or launch by typing
'baobab' in the Alt+F2 prompt or in a terminal). It is very convenient to
visually find out what takes space. For instance, have you cleaned the APT
archives (e.g., by executing 'sudo apt-get clean')? After months of use,
these archives take GB of space. Same thing about the old kernels, which are
not removed by default (you can search "linux-" in the Synaptic package
manager and remove all packages with version numbers below the one you use).
Again, you can free quite some space in this way: an image of the kernel
takes about 150 MB + 100 MB if you have its headers installed.
