How to Disable DHCP Server on OpenWRT?

As you see in the title, you can exactly disable DHCP Server on OpenWRT with editing the /etc/config/dhcp:

config 'dhcp' 'lan'
        option 'interface'  'lan'
        option 'start'      '100'
        option 'limit'      '150'
        option 'leasetime'  '12h'
        option 'ignore'     '1' 

Just add new option to your configuration:

option 'ignore' '1'

Do it for every interface that you have on your OpenWRT router.