On a machine running systemd, which TWO of these commands will power the machine off?
LPIC-1 Exam 101-500, objective 101. System architecture medium
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The options
Choose 2.
Correct systemctl poweroff
Correct. It isolates poweroff.target, which stops the remaining units, unmounts filesystems and cuts the power.
Not correct systemctl isolate rescue.target
Wrong. This switches the running system to the single-user rescue environment, stopping most services but leaving the machine on.
Correct shutdown -h now
Correct. -h requests a halt, and on a systemd system that is carried out as a power off. It is the traditional spelling of the same operation.
Not correct telinit 6
Wrong action. Runlevel 6 is reboot, and systemd maps telinit 6 onto reboot.target, so the machine comes back up rather than staying off.
Not correct shutdown -c
Wrong. -c cancels a shutdown that was already scheduled; on its own it does nothing but report that there is nothing to cancel.
Why
systemd provides several routes to the same targets: systemctl poweroff, poweroff, shutdown -h now and shutdown -P now all end at poweroff.target, while systemctl reboot, reboot, shutdown -r now and telinit 6 end at reboot.target. Note the historical difference behind -h and -P: a halt once meant stopping the CPU and leaving the machine powered, while power off cuts the power. On systemd -h behaves as power off unless -H is given explicitly.
Where this comes from
- Cited
- LPI exam objective 101.3
- What it says
- Shutting down, powering off and rebooting a system running systemd.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 101 and space the ones you get wrong.