After selecting Shutdown a number of messages appear
on the console, the last of which are:
Unmounting file systems
The system will be halted immediately.
The system then appears to hang, rather than powering
off, which is what I would have expected.
In fact, the power switch on the PC no longer
functions normally and the only way I can power the
system off is to hold down the power switch for 4
If I boot with the Safe Linux option, the PC does indeed power off after shutdown.