Suspending to RAM with hibernate-script
In this article we will explain how to accomplish a successful suspension to ram: all the processes are stopped and the current state of your machine is saved to ram. All the devices enter a low-consumption state and it will be very fast to resume the machine. Suspension to RAM is an acpi state, but the operation is almost never as simple as telling the machine to enter that state. The vast majority of laptops require additional operations and tricks. However, since this is quite an important feature for laptop users, it is worth some hours in finding the working combinations of tricks for your machine.
There is nowadays an application, called s2ram, which contains a list of existent laptop models and, according to what has been reported by other owners of these laptops, try to do the right things for that specific laptops: these laptops are 'whitelisted'. The whitelisted laptops can thus use successfully s2ram to suspend to ram. On the contrary, the non-whitelisted laptops need to try all the different command line options of s2ram in order to determine - through trial and error - the appropriate combination. Your experience, if reported to the s2ram developers, will contribute to whitelist your machine in the next release of s2ram.
However, s2ram is not the only resource: the hibernate-script, which is commonly used to accomplish Suspend to disk , supports also suspension to RAM and proposes some further tricks which could convince your machine to suspend to ram and resume properly. Moreover, the hibernate-script can automatize othere useful operations which you could want/need to do before suspension or after resuming from suspension to ram.
Thus, the first part of this article will be devoted to s2ram. The second will discuss the use of the hibernate-script in suspension to ram. In particular, we will see how the hibernate-script can be used to suspend to ram your system just with the s2ram, but providing some additional tweakings.