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Booting - Wikipedia, the free encyclopedia
A soft reboot (also known as a warm reboot) is restarting a computer under software control, without removing power or (directly) triggering a reset line. It usually, though not always, refers to an orderly shutdown and restarting of the machine.
The Control-Alt-Delete key combination on the original IBM PC was designed to allow a soft reboot for a quicker and more convenient restart than powering the computer completely down then back up.
This kind of reboot will not usually reset the hard disks, so that they have time to update their write cache to permanent storage. Hard disks will also keep their configuration (like C/H/S adjustments, HPA, DCO, internal passwords...) over these reboots.
The Linux kernel has optional support for the kexec system call, which transfers execution to a new kernel and skips hardware or firmware reboot. The entire process is done independent of the system firmware. Note that the kernel being executed does not have to be a Linux kernel.
When in doubt, use Google. Unless others can contribute, that sounds the closest to me.