Boot, reboot, shutdown using systemd

Question 1

Reboot in 5 minutes with messsage
Reboot at midnight
Reboot immediately

Answer 1

shutdown -r +5 System is going down for a reboot
shutdown -r 00:00
shutdown -r now

Question 2

Shutdown

Answer 2

shutdown -P
systemctl poweroff
systemctl halt
shutdown -h +5 system will be shut down in 5 minutes

Question 3

Cancel planned reboot

Answer 3

shutdown -c

Question 4

Show running units with type=target

Answer 4

systemctl list-units -t target

Question 5

Show the list of unit types

Answer 5

systemctl -t help

Question 6

List dependencies

Answer 6

systemctl list-dependencies

systemctl list-dependencies multi-user.target

Question 7

Main targets on the system

Answer 7

multi-user.target
graphical.target
rescue.target
reboot.target
emergency.target
(A special target unit that starts an emergency shell on the main console. This target does not pull in any services or mounts. It is the most minimal version of starting the system in order to acquire an interactive shell; the only processes running are usually just the system manager (PID 1) and the shell process. )

Question 8

Switch to another target

Answer 8

systemctl isolate multi-user.target

Question 9

Get default target

Set default target

Answer 9

systemctl get-default

systemctl set-default graphical.target

Question 10

Load into specified target while booting

Answer 10

press e to enter into grub menu
go to linux line and in the of the line append:
systemd.unit=multi-user.target
press Ctrl+x to continue the boot process

Question 11

Recover lost root password

Answer 11

when rebooting press ‘e’ to enter grub menu

1. add rd.break into the end of linux line
2. ctrl-x -to continue booting into a single mode
3. ls =>sysroot dir
4. mount -o remount,rw /sysroot
5. chroot /sysroot
6. enter ‘passwd root’ to set up new root password
7. touch /.autorelabel
8. reboot -f