Booting, Targets, Services

Question 1

Where are targets located?

Answer 1

/etc/systemd/system *called first

/usr/lib/systemd/system

Question 2

What are ways to shutdown?

Answer 2

shutdown -h
shutdown -r
shutdown -P
shutdown +3 *3 minutes
*calls systemctl shutdown

Question 3

How do you find available targets on a system?

Answer 3

systemctl list-units –type=target

Question 4

How do you find the different types of unit configuration files on a system?

Answer 4

systemctl -t help

*type

Question 5

How do you find dependencies of a target?

Answer 5

systemctl list-dependencies

i.e systemctl list-dependencies multi-user.target

Question 6

How do you get the default target?

Answer 6

systemctl get-default

Question 7

What is the multi-user.target?

Answer 7

Multiple users can be logged into the system (generally command line)

Question 8

What is the graphical.target?

Answer 8

GUI interface

Question 9

What is the emergency.target?

Answer 9

Boots into root user, mounts file system as read only

Question 10

What is the rescue.target?

Answer 10

Boots into single user environment for troubleshooting system

Question 11

What is a target?

Answer 11

A type of unit configuration file, grouping of dependencies for services, components
*another example is service

Question 12

How do you change the target you are in?

Answer 12

systemctl isolate

i. e systemctl isolate multi-user.target
* target has to be configured to move in and out of it

Question 13

Hoe do you set the default target at boot?

Answer 13

systemctl set-default

Question 14

How do you change the target within GRUB?

Answer 14

e *edit the kernel configuration
on linux16-vmlinuz- line append: systemd.unit=
i.e systemd.unit=multi-user.target

Question 15

How would you gain access to a system if the root password is forgotten?

Answer 15

Within GRUB e *edit the kernel configuration

on linux16-vmlinuz- line append: rd.break

Question 16

Once entered into initramfs how would you change a password?

Answer 16

mount -oremount,rw /sysroot *remount as read/write as it is currently write
chroot /sysroot *mount /sysroot as new root directory
passwd
touch /.autorelabel *SELinux relabels all files at next boot because the context of SELinux was changed
*contents of sysroot are to be mounted as root during final boot process

Question 17

How would you restart the network service?

Answer 17

systemctl restart network.service

Question 18

How do you check if a service is enabled?

Answer 18

systemctl is-enabled

i. e systemctl is-enabled sshd
* if .service is not specified it is assumed by default

Question 19

How do you view all disabled/enabled settings of all units?

Answer 19

systemctl list-unit-files –all

Question 20

How do you enable/disable a service?

Answer 20

systemctl enable {service}

systemctl disable {service}

Question 21

How do you start/stop a service?

Answer 21

systemctl start {service}

systemctl stop {service}