DON'T install with sudo, install in a folder in your home directory, and leave out the sudo.
$ sudo -jar forge-x.x.x-x.x.x-installer.jar --installServer
Don't do that
just do this
$ java -jar forge-x.x.x-x.x.x-installer.jar --installServer
then run it with ./run.sh so it's not in root mode.
using sudo will also cause some of the files to be unavailable if you are using a folder in your home director like I am.