In this recipe, we will use simple bash commands to access sleep modes supported by a Linux system running in QEMU (short for quick emulator).

1. Run the Raspberry Pi QEMU as described in Chapter 3, Working with Different Architectures.
2. Log in as user pi, using the password raspberry.
3. Run sudo to gain root access:

$ sudo bash
#

4. To get the list of supported sleep modes, run the following command:

 # cat /sys/power/state

5. Now switch to one of the supported modes:

 # echo freeze > /sys/power/state

6. The system goes to sleep, but we have not instructed it as to how to wake up. Close the QEMU window now.