What is cold and warm boot?

Answer 1

A cold boot occurs when the power supply is interrupted for any reason. A warm boot does not interrupt the power supply, which may result in parts of the hardware being left in an uninitialised state. When diagnosing hardware issues, a cold boot is recommended to ensure the boot is consistent. It is also best to allow at least 1 minute of inactivity to allow any residual currents to fully dissipate before restoring the power supply.

A cold boot is initiated by shutting down the system from within the OS, or by holding and then releasing the reset button, or by switching the power off at source.

A warm boot is initiated by restarting the system from within the OS.

Hibernation is akin to a cold boot as power must be interrupted. However, the machine's hardware is initialised from the memory dump created during hibernation, thus restoring the system to the exact state it was in prior to hibernation (and thus speeding up the entire boot process).

Suspension or sleep is neither a hot nor cold boot as only certain parts of the hardware are switched on and off to conserve energy. Although hardware returning from the sleep state needs to reinitialised to their previous state, the contents of memory remain active at all times, thus it is not considered a boot of any kind.

A cold boot is when a computer initializes without having run for a while, hence, it's 'cold'. For example, when you turn on your computer in the morning when it has not been on since the previous day. A warm boot is when a computer restarts after running, while it's 'warm'.

Answer 2

A cold boot - is starting up the computer from 'dead'. A warm boot - is re-starting an already running computer.