Added link to Oracle docs.
Downgrade the memory to 1G as oracle say 512 is enough.
Switch to port forwarding for oracle db connections.
Remove packages that aren't required.
Make sure the permissions on the swapfile are good.

Only root should be able to read the file.
Oracle doesn't only needs 2x memory.

So if we only have 512MB of RAM we just need 1GB of swap.
Drop the memory requirement down to 512MB.
Remove monit as a service.
Make vagrant user in the dba group.

This allows connection to sqlplus.
Disable APEX.

This stops oracle application express.
Define a service for oracle.

This allows it to be used as a dependency for other things.
Note that bc is needed for oracle install.
Remove more unneeded packages.