Mikael wrote: > 2015-10-07 0:45 GMT+08:00 Ted Unangst <t...@tedunangst.com>: > > > Mikael wrote: > > > The script below includes extra considerations to see through any kernel > > > caching of the disklabel, by rebooting between every relevant step. > > > > > > "dd if=/dev/srandom of=/dev/rwd0e bs=1024 count=1" does also wipe the > > > disklabel. > > > > > > "dd if=/dev/srandom of=/dev/wd0a bs=1024 count=1" does not wipe the > > > disklabel. > > > > > 16 partitions: > > > # size offset fstype [fsize bsize cpg] > > > a: 3907008000 16065 RAID > > > c: 3907029168 0 unused > > > e: 16001 64 RAID > > > > yes, if you overwrite the disklabel (which lives at the start of the disk) > > you > > will wipe it. don't do that. > > > > But.. wd0e is the "e" partition within the BSD disklabel, and that's what I > wrote to (and even if it's not relevant here, also its writes should be > "boundary checked" so they're foolproof in respect of overwriting > extra-partition data)? > > With "dd if=/dev/srandom of=/dev/rwd0*c* bs=1024 count=1" I'd have > understood that I wiped something sensitive, but this is "dd > if=/dev/srandom of=/dev/rwd0*e* bs=1024 count=1"?? > > > Have I (and some others) misunderstood anything about how BSD disklabelling > works?
the disklabel is the second sector of the openbsd part of the disk. *3: A6 0 1 2 - 243200 254 63 [ 64: 3907024001 ] OpenBSD so, if you overwrite sector 65, you will overwrite disklabel. normally the 'a' partition overlaps the disklabel, but you made 'e' first.
