Software Suspend 2, also called "swsusp2" and "suspend2", is an implementation of suspend-to-disk functionality in the form of a Linux kernel patch and several userspace utilities. It is an alternative to both the BIOS-driven hibernation feature found on most ThinkPad models, and the "software suspend" functionality built into recent Linux kernels.
Compared to the alternatives, Software Suspend 2 has some unique features:
- The ability to compress the memory image as it is written to disk, thereby reducing suspend and resume times.
- Saving the memory image to a file on a normal filesystem, instead of a dedicated partition.
- Cancelling a suspend in progress
- Graphical UI (optional)
- Improved reliability under some circumstances
Since it is implemented purely in software, Software Suspend 2 is in principle machine-independent and should work on all modern ThinkPad models. However, in some cases problematic driver need to be unloaded before suspension.
- ThinkPad T43: works perfectly once SATA resume patch is applied and the SATA drivers are made built-in or put in initrd (see Problems with SATA and Linux)
The project home page has a detailed HOWTO and FAQ.