On Mac OS X I had the option of creating an encrypted sparse image. I had this automount at boot and used it to store files that I wanted encrypted (tax documents, bank statements, or other personally identifiable information). It was useful because I don't want to encrypt my entire home directory, or my entire hard drive; the number of files I actually keep encrypted is pretty small so it could still be conveniently backed up to the cloud as a single file, preserving my private documents without making them accessible if someone were to gain access to that data somehow.
I'm curious if there is an analog to this on Ubuntu (or Linux in general) or if there is at least a means to achieve the same ends.
I know I can create an encrypted hard drive partition, but I don't want to do this because I want to minimize the space used while still leaving room for growth, and I want to be able to sync the file to the cloud (with a small image this is not a huge issue).
I know I can encrypt my home directory but this is not what I want to do either. I don't want to encrypt things like music, movies, configuration files, or most of the work I do since I don't care about keeping them private and I want to be able to sync a lot of it without having to update a huge blob every time I sync. I suppose theoretically I can store all my personal files in another directory and symbolically link to them from my encrypted home, but I'm still not sure if this accomplishes what I want (can I backup the blob somewhere and restore on another (not necessarily Ubuntu or Linux) machine?) or if it would cause too much of a hassle.
I've found some information about creating and mounting sparse images, but nothing I found mentioned enabling encryption.