I somehow ran into a "The maximum number of user sessions has been reached" error when working on a new Cisco BE6000 / UCS C220 chassis install. I had previously updated all the chassis software using the Host Upgrade Utility so I imagine it may have somehow been just me.
To fix things you can SSH to the CIMC address and run:
To change to a particular session from the resulting list, note the session index numbers from the user-session list and run:
scope user-session sessionindex
To end the session you just switched to, run:
To exit the scope of that session, run: