If you encounter that Centos freezes when booting then hit the escape key on order to bring forward the kernel messages. If you see the SELinux failed to load follow these instructions to fix it.
At boot hit the E-key - you'll get into the boot system Grub.
Arrow down to the line that begins with linux16
Press the end key on your keyboard in order to get to the end of the line.
Enter a space and then selinux=0 NOTICE here, you're using a US keyboard which mean on a Danish keyboard the = key is the key with ', ` and | often just to the left of the backspace key.
Now press Ctrl-X - the system will reboot.
When booted open a terminal and type this
]$ sudo yum remove selinux-policy
answer y the the question.
Next is to reinstall the selinux-policy by typing
]$ sudo yum install selinux-policy
Finally type in
]$ reboot now
Your system should boot correctly now.