I have a root lvm with 10 GB, most of which is used, and a /home lvm with 877 GB. I want to resize the /home lvm to free up space, and then allocate that to root. I'm not clear on whether I can dynamically resize the partitions while mounted, but as far as I can tell, that's not possible. Also, as far as I can tell, I can't unmount /home or root unless I'm using a rescue disk.
Normally if I wanted to resize a disk partition that I couldn't otherwise unmount, I would use a gparted live disk. But as far as I know, gparted only works on "real" partitions, and can't operate on lvm partitions. So what's the best way to get access to the unmounted partitions and resize them?