Linux Server: online resize root partition

Question

I have an Ubuntu Server hosted at Aruba Cloud and I want to resize the root partition...
The current partition scheme is (roughly):

sda1  /boot  300MB
sda2  swap    ? MB
sda3  /       10GB
<FREE SPACE>  10GB

Is there any way I can extend sda3 at the max?
I've tried with parted or cfdisk but they won't allow me to do it because it's in use...

My idea was to enlarge sda3 in the Partition Table (not the FS) and then use resize2fs to online resize it.

Answer 1

repartitioning alone (without the kernel reflecting the changes) of /dev/sda3 shouldn't be an issue with cfdisk. A reboot is not required for this. But after this before you online resize sda3 (e.g. by 'resize2fs -p /dev/sda3') you indeed must reboot. Otherwise your running kernel does not adopt the new partitioning.