Well our cobbler is modified to do additional API it didn't originally support. I do not expect third-parties to be able to use os_type for dynamically re-imaging machines. The plana01 is a special machine that is not in the teuthology lock database that runs several important service (like cobbler). I could have this specified in the teuthology yaml but it seems like just one more thing to litter up that file/configure when its not going to ever be changing.