Boot2 loading process

Valentin Nechayev netch at
Sat Oct 14 11:31:01 PDT 2006

 Sat, Oct 14, 2006 at 09:41:01, jan.pfeifer wrote about "Boot2 loading process": 

> I was reading through the architecture handbook ( about the boot process, and something strange caught my attention.

>  According to the docs boot0 loads only the first record of the partition, that is 512bytes. But boot2 in my 4.11 freebsd has > 7K in size -- what makes sense, considering the amount of things it does and that it links btxld.
Name it "slice", not "partition".

> So my question is: where does the rest of the boot2 binary is located and how is it loaded ?

You skipped boot1 from attention. boot2 is loaded by boot1, not boot0.
boot1 resides in first block of FreeBSD slice (or whole disk in dedicated
partitioning). It reads MBR, detects first active FreeBSD slice (or first
FreeBSD slice if none active), loads first 8K from its (they are boot1
+ disklabel + boot2) and passes control to boot2. boot2 is placed in
blocks 2-15 of the FreeBSD slice.

> thanks in advance for any answers!


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