CentOS Stream 9 : Initial Settings : Add User Accounts

To add user accounts on CentOS Stream Server, Configure like follows.
[1] For example, Add [centos] user.

[root@localhost ~]# useradd centos
[root@localhost ~]# passwd centos
Changing password for user centos.
New UNIX password:              # input any password you'd like to set
Retype new UNIX password:       # confirm
passwd: all authentication tokens updated successfully.

[2] If you'd like to switch to root account from a user added above, use [su] command to do so.

localhost login: centos         # login username
password:                       # input user password
[centos@localhost ~]$ su -      # switch to root
Password:                       # input root password
[root@localhost ~]#             # just switched to root

[3] If you'd like to limit users to run [su] command, configure like follows.
On the example below, only users in [wheel] group can run [su] command.

[root@localhost ~]# usermod -aG wheel centos
[root@localhost ~]# vi /etc/pam.d/su
#%PAM-1.0
auth            sufficient      pam_rootok.so
# Uncomment the following line to implicitly trust users in the "wheel" group.
#auth           sufficient      pam_wheel.so trust use_uid
# Uncomment the following line to require a user to be in the "wheel" group.
# uncomment the following line
auth            required        pam_wheel.so use_uid
auth            substack        system-auth
auth            include         postlogin
account         sufficient      pam_succeed_if.so uid = 0 use_uid quiet
account         include         system-auth
password        include         system-auth
session         include         system-auth
session         include         postlogin
session         optional        pam_xauth.so

# verify settings with a user who is not in allowed group
[redhat@localhost ~]$ su -
Password:
su: Permission denied     # denied normally

[4] If you'd like to remove a user accounts, Set like follows.

# remove a user [centos] (only removed user account)
[root@localhost ~]# userdel centos
# remove a user [centos] (removed user account and his home directory both)
[root@localhost ~]# userdel -r centos