1. SELinux shutdown of Linux

By default, SELinux contains the policy for DHCP, so close SELinux and restart the DHCP service to start it

method:

1) Temporary shutdown (no machine restart): setenforce 0       ## Set SELinux to permission mode       　　　　　　　　　　　　　　                                                                             ## Setenforce 1 sets SELinux to enforcing mode

2) To modify the configuration file, you need to restart the machine: modify the/etc/SELinux/config file, change SELinux = enforcing to SELinux = disabled, and restart the machine

2. By modifying dhcpd to root, the policy management of SELinux is bypassed

Reproduced in: https://blog.51cto.com/qiansi/1966572