: ~ ; d disklabel -Ev sd2
Treating sectors 256-4294852800 as the OpenBSD portion of the disk.
You can use the 'b' command to change this.

Label editor (enter '?' for help at any prompt)
sd2> ?
Available commands:
 ? | h    - show help                 n [part] - set mount point
 A        - auto partition all space  p [unit] - print partitions
 a [part] - add partition             q        - quit & save changes
 b        - set OpenBSD boundaries    R [part] - resize auto allocated partition
 c [part] - change partition size     r        - display free space
 D        - reset label to default    s [path] - save label to file
 d [part] - delete partition          U        - undo all changes
 e        - edit drive parameters     u        - undo last change
 g [d|u]  - [d]isk or [u]ser geometry w        - write label to disk
 i        - modify disklabel UID      X        - toggle expert mode
 l [unit] - print disk label header   x        - exit & lose changes
 M        - disklabel(8) man page     z        - delete all partitions
 m [part] - modify partition

Suffixes can be used to indicate units other than sectors:
 'b' (bytes), 'k' (kilobytes), 'm' (megabytes), 'g' (gigabytes) 't' (terabytes)
 'c' (cylinders), '%' (% of total disk), '&' (% of free space).
Values in non-sector units are truncated to the nearest cylinder boundary.
sd2> p
OpenBSD area: 256-4294852800; size: 4294852544; free: 4294852544
#                size           offset  fstype [fsize bsize   cpg]
  c:      11721045168                0  unused                    
sd2> a
partition: [a] 
offset: [256] 
size: [4294852544] 100%
FS type: [4.2BSD] 
sd2*> p
OpenBSD area: 256-4294852800; size: 4294852544; free: 64
#                size           offset  fstype [fsize bsize   cpg]
  a:       4294852480              256  4.2BSD   8192 65536     1 
  c:      11721045168                0  unused