This is an excerpt from an install log notebook I kept when reinstalling my system that includes just the parts relevent to Dropbox.
This whole OS installation was precipitated by the fact that Dropbox dropped support for all Linux filesystems except for plain ext4, so it wasn't working with ecryptfs and LVM and all the default ways Ubuntu sets up the filesystem.
However, Dropbox does work with full-disk encryption and an ext4 filesystem. The technology for full disk encryption under Linux is LUKS.
The key things I need to make sure happen when setting up my partitions and installing the system are: