I downloaded the oracle vm templates for enterprise manager 12c.
All setup went well, but when i look at the / filesystem i see only about 1000 mb free space.
How can i add more disk space to the / filesystem.
I want to update this virtual machine, but i am worried the / filesystem runs out of space.
The Oracle VM Manager allows you to resize or add a virtual disk. You could check the Oracle VM documentation or perhaps use a procedure similar to http://www.novell.com/support/kb/doc.php?id=3786220. Your issue rather belongs to the Oracle VM forum.