partition sizes in 4BSD systems

[John Gilmore]

In article <100 at hadron.UUCP>, jsdy at hadron.UUCP (Joseph S. D. Yao) writes:
> For BSD, the root partition is always 15884 sectors ("blocks" is
> not a good term here, although the code uses it).  This is nice
> and reasonable for an RP0[456].  It is minimal for the others.
> Being LCD, it is thus the standard.  This will usually not completely
> cover a cylinder on other drives, leading to problems when dd'ing
> using a multiple of the cylinder size.  Partition B, often used
> as swap, is 33440 sectors long.

Hmm, I always wondered where those numbers came from.  On my Sun-3:

# dkinfo sd0
sd0: SCSI controller at addr 200000, unit # 0
1022 cylinders 8 heads (base 2) 17 sectors/track
a: 15884 sectors (116 cyls, 6 tracks, 6 sectors)
   starting cylinder 0
b: 33440 sectors (245 cyls, 7 tracks, 1 sectors)
   starting cylinder 117
c: 138448 sectors (1018 cyls)
   starting cylinder 0
g: 89080 sectors (655 cyls)
   starting cylinder 363

      :-) !!!

PPS: I repartitioned the other drives though, so they use whole cylinders.