Understanding the FreeBSD Startup Process

When an operating system starts up after you power it on, it undergoes a rather remarkable transformation from a dormant set of ones and zeroes on a disk to a humming, vibrant creature with hundreds of interacting processes jostling with each other throughout memory and the disks. When you think about it, the capability of an operating system to “pull itself up by its own bootstraps”—or, as we term it colloquially, to “boot”—is quite a feat. It's comparable to a clutch in a car, allowing the engine (which must be running, even when the car is stopped) to gradually transfer power to the stopped wheels so that they can start turning without killing the engine.

The computer's hardware BIOS, or basic input/output ...

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