I'm thinking of using eCryptFS, but I wanted to know how much more disk space is used.
I did some testing that indicated eCryptfs has a minimum file size of 12,288 bytes, and seemed to add about 8k to larger files (as Colin correctly says).
For example, a file that's 10,485,760 bytes ends up encrypted as 10,493,952 bytes, so increased by 8,192 bytes.
Not significant for large files, but for lots of tiny files (like home configuration files usually are, or some other applications) the size could balloon significantly. Even a 1 byte file becomes 12,288 bytes.
You can just add a new user with
sudo adduser --encrypt-home newguy then login (in a terminal if you don't want to log out of your regular user -
sudo login) and experiment & compare the different file sizes yourself.
Encrypted files are in
/home/.ecryptfs/newguy/.Private/ and (when logged in) the decrypted versions are in
eCryptFS has some quirks, like long filenames (over ~200 characters) may not work or be truncated, and file permissions may not work so well (
chmod seems to report success, but
ls keeps listing
----------. If you want a fixed size encrypted container file (or partition) you could use LUKS too/instead.