If you need to reboot a 6248 Fabric Interconnect manually here is one method of doing so. Let's say your have a clustered pair and you need to reboot the subordinate. One Method would be to SSH the UCS CLI and type the following command to connect to the subordinate:
UCS-Fabric-A#connect local-mgmt b
this will bring you to the following
From here you can type the command "reboot"
Hope this helps.