Copy provides 15GB of free space online in a Dropbox like two-way sync and cloud storage. The reason I tried it was that it has clients for almost all systems, including Linux, Android and even Raspberry Pi!
Download the Linux client from here. It worked with both Ubuntu and Raspberry Pi.
Unzip the contents to a suitable directory. The client binary will be run from this location on every restart of your system, so choose the location well.
Both commandline and GUI clients are available. I used the GUI client on my desktop Ubuntu and commandline client on my Raspberry Pi.
x86_64build of the client. I like that the GUI client works just like Dropbox: stays in system tray and has similar UI. You just need to run it the first time:
$ ./x86_64/CopyAgent &
armv6hbuild of the client. I call the client by specifying the sync directory to use, the login, the password and also request it to run in the background as daemon:
$ ./armv6h/CopyConsole -root=/my/sync/dir -firstname.lastname@example.org -password=hushhush -daemonize
Tried with: Copy 1.48.0456, Ubuntu 14.04 and Raspbian 7