11-01-2020

https://youtu.be/UxK_uzWrc10

Runlevels

Runlevel is a operating state of a system

[root@zmpt01 ~]# who -r

run-level 3 2020-11-01 15:22

[root@zmpt01 ~]# runlevel

N 3

[root@zmpt01 ~]# systemctl get-default

multi-user.target

Linux has 7 runlevels

Runlevel 0	Shutdown mode	Init 0
Runlevel 1	Rescue, Emergency Mode – No Network	Init 1
Runlevel 2	Multi-UserMode – No NFS	Init 2
Runlevel 3	Mult-UserMode with NFS – default	Init 3
Runlevel 4	Not Used
Runlevel 5	Graphical User Mode – GUI	Init 5
Runlevel 6	Reboot	Init 6

Unless you the default runlevel, the system will boot into whatever default runlevel is

Set the default run level

systemctl set-default

- This command is used for changing default run level

- Whenever you use this command

- The symbolic link for the file /etc/systemd/system/default.target

- Is changed to the the file associated with the desired runlevel file

- Runlevel files are sitting in this location

- Most of the time you are only setting default either Multi-User or Graphical

- Runlevel 3 or Runlevel 5

During the system boot process

/etc/systemd/system/default.target

This file is actually a symlink of the targeted runlevel file

Most common is either 3 or 5

Main file read during system boot	/etc/systemd/system/default.target
Systemctl set-default	This command will chaged the symlink to either one fo the file
Multi-user.target	/usr/lib/systemd/system/multi-user.target
Graphical.target	/usr/lib/systemd/system/graphical.target.

Set the default to graphical

[root@zmpt01 ~]# systemctl set-default graphical.target

Removed symlink /etc/systemd/system/default.target.

Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/graphical.target.

[root@zmpt01 ~]# systemctl get-default

graphical.target

[root@zmpt01 ~]# stat /etc/systemd/system/default.target

File: ‘/etc/systemd/system/default.target’ -> ‘/usr/lib/systemd/system/graphical.target’

Size: 40 Blocks: 0 IO Block: 4096 symbolic link

Device: fd00h/64768d Inode: 2965052 Links: 1

Access: (0777/lrwxrwxrwx) Uid: ( 0/ root) Gid: ( 0/ root)

Context: system_u:object_r:systemd_unit_file_t:s0

Access: 2020-11-01 16:05:23.881107580 -0600

Modify: 2020-11-01 16:05:23.702105238 -0600

Change: 2020-11-01 16:05:23.702105238 -0600

Birth: -

Set the default to multi-user

[root@zmpt01 ~]# 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.

[root@zmpt01 ~]# systemctl get-default

multi-user.target

[root@zmpt01 ~]# stat /etc/systemd/system/default.target

File: ‘/etc/systemd/system/default.target’ -> ‘/usr/lib/systemd/system/multi-user.target’

Size: 41 Blocks: 0 IO Block: 4096 symbolic link

Device: fd00h/64768d Inode: 2965067 Links: 1

Access: (0777/lrwxrwxrwx) Uid: ( 0/ root) Gid: ( 0/ root)

Context: system_u:object_r:systemd_unit_file_t:s0

Access: 2020-11-01 16:10:03.827399630 -0600

Modify: 2020-11-01 16:10:03.645397251 -0600

Change: 2020-11-01 16:10:03.645397251 -0600

Birth: -