How to Boot systems into different targets manually on CentOS 7 / RHEL 7

RHCSA Exam Objectives: How to Boot systems into different targets manually
In this lesson we are going to learn how to boot systems into different targets manually on the Red Hat Enterprise 7 server (RHEL)

Runlevel	Target Units	Description
0	runlevel0.target, poweroff.target	Shut down and power off the system.
1	runlevel1.target, rescue.target	Set up a rescue shell.
2	runlevel2.target, multi-user.target	Set up a non-graphical multi-user system.
3	runlevel3.target, multi-user.target	Set up a non-graphical multi-user system.
4	runlevel4.target, multi-user.target	Set up a non-graphical multi-user system.
5	runlevel5.target, graphical.target	Set up a graphical multi-user system.
6	runlevel6.target, reboot.target	Shut down and reboot the system.

Viewing the Default Target

To determine which target unit is used by default, run the following command:

# systemctl get-default

Viewing the Current Target

To list all currently loaded target units, type one of the following commands:

# systemctl list-units --type target
# systemctl list-units --type target --all

Changing the Default Target

 
– To configure the system to use a different target unit by default use the following command:

# systemctl set-default name.target

Replace name with the name of the target unit you want to use by default.

Example:

 
[[email protected] ~]# systemctl set-default multi-user.target
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.
[[email protected] ~]#

Changing the Current Target

To change to a different target unit in the current session, type the following command:

# systemctl isolate name.target 

Replace name with the name of the target unit you want
Example 1:To turn off the graphical user interface and change to the multi-user.target

[[email protected] ~]# systemctl isolate multi-user.target

Example 2:Changing to Rescue Mode

[[email protected] ~]# systemctl isolate rescue.target

Notice here, that we can use other commands to do the same task:

[[email protected] ~]# systemctl rescue
[[email protected] ~]#  systemctl --no-wall rescue #this command will not send message to currently logged users

Example 2:Changing to Emergency Mode

[[email protected] ~]# systemctl isolate emergency.target

Notice here, that we can use other commands to do the same task:

[[email protected] ~]# systemctl emergency
[[email protected] ~]#  systemctl --no-wall emergency #this command will not send message to currently logged users