Clonezilla
Clonezilla is a free software disaster recovery, disk cloning and deployment solution. You're probably familiar with the popular proprietary commercial package Norton Ghost®.
Incrementally clones linux drives. WereSync can clone to a smaller drive, from a drive currently running, and creates new UUIDs, so the two drives can be used alongside...
weresync takes a linux hard drive and effectively clones it, but works incrementally so you don't have to spend so long backing up each time. additionally, weresync can clone to a smaller drive, if your data will fit on the smaller drive. because weresync uses rsync to copy, it can copy a running drive, though certain parts of state may not be preserved.
all of this comes packaged with a simple gui, or a single command line, making weresync accessible to anyone using linux.
backup-and-restore synchronization disk-cloning incremental linux bootable-backup