We’re all familiar with the hibernate/deep-sleep features that are typical on your standard laptop. In this mode, the entire contents of RAM are written to the disk and the machine is completely shut down. When it’s next booted, the system is restored to the exact state it was at before sleep, with all of your programs running just like they were when you left them.

What if you could do this at the process level? You could kill whatever umpteen-gazillion applications you have running, reboot your computer, and then start your apps back up whenever you like and they would be exactly the way they were when you left them.

There’s a Linux application called CryoPID which attempts to do just that.

CryoPID requires no special kernel modifications and operates in user mode, so you don’t need to be root. All you do is run the freeze program on a process you own:

freeze /tmp/savestatefile 1234

This will archive the state of process 1234 into a self-executing, compressed file named /tmp/savestatefile. To start it back up, just run the save file:

/tmp/savestatefile

When this is executed, your application will be restored, relinked to any previously-loaded DLLs, and attached to the file descriptors it had open.

You’ll run into some problems with network socket connections you had open, and support for X applications is still only experimental, so the useful scenario is a bit limited, but it’s a promising concept and could come in quite handy in the command-line world.

CryoPID – A Process Freezer for Linux