Verifique o arquivo /etc/default/halt
Este arquivo contém uma configuração de variável que informa ao halt
como ele deve se comportar.
OPTIONS
The following variables can be set.
HALT If set to poweroff the system will be powered down after it has
been brought down. This is the default.
If set to halt the system will only be halted after it has been
brought down. What exactly this means depends on your hardware.
NETDOWN
Setting this to no prevents shutdown from shutting down the
network intefaces. This is necessary to use Wake-On-Lan.
Setting it to yes causes shutdown to also bring down the network
interfaces (and thus prevent the machine from being woken up
remotely).
HALT
provavelmente está definido como halt
em vez de poweroff
.
Do meu sistema: more /etc/default/halt
# Default behaviour of shutdown -h / halt. Set to "halt" or "poweroff".
HALT=poweroff