What's the difference between halt and shutdown now?

Question

halt can turn off the machine,

but shutdown now doesn't turn off ,it just logs the root off.

Anyone knows the reason?

Answer 1

On a modern Linux systems halt calls shutdown with a suitable argument -h (halt) or -r (reboot) these are the equivalent of runlevels 0 and 6. Running shutdown now puts the system into runlevel 1 (single user mode). If you want to halt the system with shutdown use shutdown -h now.

On Solaris 10/11 halt is quite brutal, it just flushes the disk caches and powers off the system - no attempt is made to run any scripts or shutdown smf facilities.

Other systems may do things differently too.

Answer 2

I assume Linux? (Good practice to tell or at least tag the OS).

'shutdown now' puts the system in init 1, while 'shutdown -h now' halts it 'now'.

From the manual of shutdown

shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to halt the system, runlevel 6 is used to reboot the system, and runlevel 1 is used to put to system into a state where administrative tasks can be performed; this is the default if neither the -h or -r flag is given to shutdown. To see which actions are taken on halt or reboot see the appropriate entries for these runlevels in the file /etc/inittab.

Answer 3

thats a "long time ago" commands. shutdown or poweroff -- turnoff computer halt -- prepares computer to be shutted down after user push the power button.