  $ osdmaptool
  osdmaptool: must specify osdmap filename
   usage: [--print] [--createsimple <numosd> [--clobber] [--pg_bits <bitsperosd>]] <mapfilename>
     --export-crush <file>   write osdmap's crush map to <file>
     --import-crush <file>   replace osdmap's crush map with <file>
     --test-map-pg <pgid>    map a pgid to osds
  [1]
