Solved freebsd-boot size

circus78

Active Member

Thanks: 6
Messages: 201

#1
Hi, I have some doubt about freebsd-boot partition size. According to Handbook:

https://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html

"the freebsd-boot partition should be no larger than 512K due to current boot code limitations"
.

On same page, I see an example (figure 2.15) in which freebsd-boot partition is 64kB.

Even on one of my machines (I am pretty sure I used the "guided" partition scheme), I see this:

Code:
# gpart show
=>       34  167772093  da0  GPT  (80G)
         34        128    1  freebsd-boot  (64K)
        162  159383424    2  freebsd-ufs  (76G)
  159383586    8388540    3  freebsd-swap  (4.0G)
  167772126          1       - free -  (512B)
Can you give me some clarification? Is 512K really a limitation for such partition?
Thank you very much
 

swegen

Member

Thanks: 51
Messages: 75

#2
From gpart():
This partition must be larger than the bootstrap
code (either /boot/gptboot for UFS or /boot/gptzfsboot for ZFS), but
smaller than 545 kB since the first-stage loader will load the entire
partition into memory during boot, regardless of how much data it
actually contains.
This is pretty much the maximum size as the whole partition is loaded into memory in Real Mode. I usually create the freebsd-boot partition as 1024 sectors (512K) which is also a nice round number.
 
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