Traditionally, the command
sudo shutdown now will take you to the runlevel 1 (recovery mode); this will happen for both Upstart and SysV init. To get what you want, i.e., to shut down the computer properly, you need to give the
-h switch to
One thing to note here is that
halt will close all the processes, turn off the CPUs and return the control to a ROM monitor of the mainboard needing the user to press the power button to get the power supply turned off, whereas
poweroff after turning off the CPUs will simply turn off the power supply resulting in a proper shutdown.
-h switch of
shutdown will either
poweroff the computer, the decision will be taken by the system although in Ubuntu I have seen that it would normally
poweroff the machine. To be sure of that, you can use the
-P switch with
poweroff the computer.
To summarize, here are the commands available to
halt) a computer:
sudo shutdown -h now
sudo shutdown -P now
sudo halt -p
sudo init 0
halt commands basically invoke
shutdown (except for the
sudo poweroff and
sudo halt -p are exactly like
sudo shutdown -P now. The command
sudo init 0 will take you to the runlevel 0 (shutdown).
Now what if you want to shut down forcefully, i.e., you don’t want to wait for processes to close normally? In that case you can use:
sudo poweroff -f
This will not use
shutdown. Rather, it will invoke the
reboot(2) system call (used for reboot, poweroff & halt) to power off the computer instantly.