If the Linux server fails on boot with a message like this,You should add a parameter in grub boot editor which appears on boot.

When your server opens kernel list will appear on your screen.You use the arrow keys a kernel line like “Centos Linux 7 (Core) with Linux….” and type “e” button to edit.

After that,find the line which starts with linux add “selinux=0” like this below and type Ctrl button+x.Your server will open normally.After your server boots,fix the main problem about selinux that you have previously changed