IRC, freenode, #hurd, 2011-08-25:

< frhodes> how can I replace an existing running server with a new one
  without rebooting?
< antrik> frhodes: depends. if other critical things depend on it, you
  can't. there is no mechanism to serialize and pass on the open sessions
< antrik> in some situations, you can orphan the old translator while
  starting a new one, so the previous clients will stay with the old one
  while new one will get the new one
< antrik> obviously that only works for things that aren't exclusive by
  nature
< antrik> in some cases, you might even be able simply to remove the old
  translator... but obviously only for non-critical stuff :-)