If the machine is new or offline, DCOps will need to physically boot, attach a keyboard, and netboot.
Re-imaging a machine
If the machine is already online and accessible, Lion machines can be re-imaged automatically via netboot. Instructions are in mana. If the machine is idle, you can reboot it immediately.
Assuming the machine is enabled in slavealloc, it will enter production automatically.
ssh keys (build slaves only)
If the machine is a 10.7 builder (i.e. bld-lion-r5), it will need either the production, try, or staging ssh keys, depending on which pool it is assigned to in slavealloc.
The easiest way to get the proper keys is to |scp -r| the .ssh/ dir from an existing, known-good host from the same slave pool.