When configuring the Linux server, when you need to modify the configuration file of the system, you should do a good job.
If you configure DHCP Server, you generally need to modify the /etc/dhcpd.conf file, then you should make a backup proper configuration file.
Simple backup method: cp /etc/dhcpd.conf /etc/dhcpd.conf.old
If it is configured for important servers, it is recommended to do a written note, record detailed time characters and modified configurations and their description.
