Leading 16 block free space in BSD label still relevant?

A

aragon

Hi

Not so long ago BSD labels needed a 16 block (8k) free space area at their start (partition "a" with 16 block offset), reserved for metadata. This is still documented in bsdlabel(8) to this day, but gpart(8) doesn't seem to care about it.

Anyone know if it is still required?
 
Code: 
# /dev/ad0s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a:  2097152        0    4.2BSD     2048 16384 28552
I believe this one was created using sysinstall's bsdlabel.

Do you have an idea what this metadata is used for? Maybe I don't have any problems because I don't use a particular disk/file system feature...
 
I think these 16 blocks were reserved for the boot loader when using Dangerously Dedicated mode, i.e. bsdlabeling the disk directly instead of containing it inside an MBR slice.

The file /boot/boot is this loader and it is exactly 8192 bytes (16 blocks) in size.
 
Mmm, that would suggest that it's still needed then, at least for BSD labels that are booted.

Are you booting off yours, Beastie?
 
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