Install OSX Parallels version 10 / 11 tools on Ubuntu server guest.
Create Ubuntu server instance under Parallels (obviously).
Start VM, goto Actions - Install Parallels Tools... to mount the ISO image.
Devices > CD/DVD 1 > Connect Image..../Applications/Parallels Desktop/Contents/Resources/Tools/prl-tools-lin.iso.From the terminal, run the following commands:
$ sudo su
$ apt-get install gcc make
$ mkdir -p /media/cdrom
$ mount /dev/cdrom /media/cdrom
$ cd /media/cdrom
$ ./install
Follow prompts to install tools.
Reboot
Host shares should now be mounted in Ubuntu guest via the just installed prltoolsd service, set to start on system boot-up.
All done