The startup process
From Linux 101, The beginner's guide to all things Linux.
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[edit] Non-Linux specific
This section is general computer information, and is good to know regardless of whether or not you use Linux.
[edit] BIOS
When you power up your computer, your BIOS or Basic Input/Output System takes control of the machine. Your motherboard has at least 1 chip which is the BIOS (some manufacturers actually have two on the motherboard for security of if one fails).
The BIOS, like all steps to starting the computer, is critical. It brings order to the devices on the system and makes them communicate without disrupting one another. It also takes its first glance to identify system components such as which device is a CD-ROM or a harddrive, and so forth.
In later years the BIOS has been shifted from permanent hardware to a firmware design, where manufacturers could release updates for the BIOS after realizing they made mistakes or oversights. This is what brought about the second BIOS chip on systems, as an incomplete firmware update usually ends as a sob story.
The BIOS also stores several system settings such as the clock and peripheral configuration usually related to performance or reliability. Motherboards equipped with thermal sensors also store their values through the BIOS.
[edit] Boot loader
After the BIOS has identified devices, it selects from the preferences mentioned above one device as the first to boot. This is where the boot loader comes in.
[edit] Linux Specific
After your boot loader starts Linux, you start seeing a lot of text messages scrolling by quickly. These are your kernel messages. Mostly the system is just identifying hardware.
There is one important thing to point out here. When you make a kernel from the source code, you run the command:
- #
make bzImage
The bz in bzImage is refering to the bzip2 file compression. This is why when you boot your computer it says "Decompressing kernel..."
