In Superuser mode, type
halt and then press Enter. Then, at the halt confirmation prompt, answer
y followed by Enter.
ACMEPACKET# halt
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WARNING: you are about to halt the SD!
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Halt this SD [y/n] ? : y
Preparing for system shutdown
Syncing and unmounting filesystems
Flushing sd devices
Powering off.......
Sent SIGKILL to all processes
Requesting system power off
Disabling non-boot CPU’s........
Power down.