script. The old script is just a wrapper that asks the page for the
  real script, which is run on the node. We return a url and md5 in
  the response, which the node then gets with wget. Right now the md5
  and the url are hardwired in the page, and the script goes in
  /z/testbed/distributions on boss. Needs to be DB loaded instead. The
  node will wait forever until it can get the script. ^C on the
  console will drop the node into a shell if the user knows the root
  password.

  Security is flimsy still; we depend on the ssl connection to ensure
  that the script is really coming from emulab. Should probably sign
  the script.