Power on, POST, and Boot

Power on, POST, and Boot: Which is which?

<graphvizl>

 digraph D {

  node [fontname="Helvetica", fontsize="11"]
  edge [fontname="Helvetica"]

  poweron        [label="POWER ON", shape="box", style="bold"]
  post           [label="POST", shape="box", style="bold"]
  boot           [label="BOOT", shape="box", style="bold"]

  poweron -> post -> boot

 }

</graphvizl>

Power on

is what happens when the systems first gets electricity. You may hear a beep or a fan or see the lights come on.

POST

means Power On Self Test and is a basic system check that happens once the system has powered on successfully.

Boot

means the computer is loading an operating system, typically off of the hard drive (but it also could load the OS off of a floppy, a CD, or even over the network).

If you see a system trying to boot, then you know it must have POSTed. This means that if you see an OS load (i.e. a system boots to Windows or Linux) then the POST was successful. Likewise, if you see a message similar to "Operating System not found" then the boot is failing, but of course this also mean that the system successfully POSTed.

NOTE: We never want to boot from an OS. We, however, do want to try to get the system to POST.