What owner and permissions do i set, when i deploy a Pharo/Seaside application on Ubuntu for the VM, the image and for the directory containing those files? I also use Object Serialization as described in the Seaside Book as persistence strategy.
It depends how your setup looks like.
I like to create a user (named for example 'seaside') dedicated to running a Seaside application. I install the VM and image in the seaside home directory and run it as seaside. So all the ownership is for the 'seaside' user.