Mikael wrote: > 2015-10-07 0:58 GMT+08:00 Ted Unangst <t...@tedunangst.com>: > > > > 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. > > > > Ugh, ok - just to settle this one forever I hope, four brief Q:s: > > 1) Does this mean that on an ordinary disk (where the "a" partition is the > disk's first partition, and starts at the offset autogenerated as default > option by the "disklabel" tool), the start of the "a" partition" actually > overlaps with disklabel-internal data?
Yes. So, the metadata on a x86 disk will look like: |start ---------------------------------------------- end| |MBR . somestuff | OpenBSD partition --------------------| | .............. | disklabel ----------------------------| | .............. | FFS 'a' ---- | swap 'b' --- | FFS 'd' | FFS knows it should not use the first few sectors of a partiton, because other things may live there. This may not be obvious to start, but if you think about it, these data structures have to live *somewhere*. If you cannot see reserved space between areas of disk, then the reserved space must be somewhere inside those areas.
