Wikipedia
CRIU
Checkpoint/Restore In Userspace, or CRIU (pronounced kree-oo, ), is a software tool for the Linux operating system. Using this tool, it is possible to freeze a running application (or part of it) and checkpoint it to persistent storage as a collection of files. One can then use the files to restore and run the application from the point it was frozen at. The distinctive feature of the CRIU project is that it is mainly implemented in user space, rather than in the kernel.
The project is currently under active development.