Suspend and resume your computer

We’ve talked about what happens when you start your computer from cold, and touched on what happens when you shut down, but that isn’t the only way of turning a computer on and off.

Sleep and hibernation are ways of turning a computer off without turning it off. They save the computer’s current state and restore it when it’s turned back on. This saves time on both shutdown and startup and also means you can carry on where you left off with all your applications still open.

While originally intended for laptops, sleep and hibernate are becoming increasingly popular for desktops too. In sleep mode, the computer enters a low-power mode where the contents of memory are preserved but most other functions are shut down. This gives instant restarts but still consumes some power because the memory is kept alive. Hibernate saves the contents of memory to your hard disk, usually in the swap partition, before shutting down the computer. On reboot, the kernel spots the presences of hibernated data and loads it back into memory.

Using a combination of these two means you may never need to shutdown or reboot your computer unless you update the kernel or want to add hardware.