typically you ssh using Putty or Terminal (Mac) into miner as
ssh root@[yourmineripaddress]
it will ask for root password, type root, then return/enter
root: poweroff -d [number of seconds]
root: exit
instead of [your miner address] type 192.168.1.99 (or whatever)
instead of [number of seconds] type a simple number (2,3, etc), then don't forget to hit enter/return
this works great-very mild treatment of the machine with no X on restart. X could happen if you were overclocking, then switch PSU off and very soon back on.