vinum setup

[synrat]

4.8

I'm trying to setup partitions for vinum.
I am in single user mode, but every time I try
to modify swap size to accomodate for vinum confuration
I get

disklabel: ioctl DIOCWDINFO: open partition would move or shrink
re-edit the label? [y]

#        size   offset    fstype   [fsize bsize bps/cpg]
  a: 21094400  2109440    4.2BSD     2048 16384    89   # (Cyl.  131*-
1444*)
  b:  2109000      430      swap                        # (Cyl.    0 -
131*)
  c: 156248127        0    unused        0     0        # (Cyl.    0 -
9725*)
  e: 133044287 23203840    4.2BSD     2048 16384    89  # (Cyl. 1444*-
9725*)
  h: 156248111       16     vinum                       # (Cyl.    0*-
9725*)