DHCP daemon on Raspberry Pi

DHCP stands for “Dynamic Host Configuration Protocol”.    The DHCP daemon is the process which assigns IP addresses to computers when they join a network, and gives them other important information about the network.

Here is how to set up and configure dhcpd on Raspbian Stretch:

1. Install: Install the package:
   sudo apt-get install isc-dhcp-server
   When you install this package it is configured to run automatically at boot time.
2. Configure: There are two files to edit:
   1. 1. Move the existing file /etc/dhcp/dhcpd.conf out of the way so you can replace it with your own:
         sudo mv /etc/dhcp/dhcpd.conf /etc/dhcp/dhcpd.conf.ORIG
         (You should keep it because it contains good documentation and examples).
         Then create and edit a new file /etc/dhcp/dhcpd.conf containing:¹

         #                                                                               
         # Configuration file for DHCP server on Rasberry Pi                             
         #                                                                               
         ddns-update-style none;
         option domain-name "wifipi.local";
         option domain-name-servers 8.8.8.8;
         default-lease-time 3600;
         max-lease-time 86400;
         authoritative;
         log-facility local7;
         
         # Configure service for local network 192.168.47.0 (the wireless AP)                    
         subnet 192.168.47.0  netmask 255.255.255.0 {
             range 192.168.47.50 192.168.47.250;
             option routers 192.168.47.1;
         }
         ##

      2. Also edit the file /etc/default/isc-dhcp-server to add the line:

         INTERFACESv4="wlan0"

         Change the name of the interface if you are using something else.  (My setup actually runs dhcpd on wlan1.)

3. Restart: The service should already be enabled, and is probably already running. Restart it with
   sudo systemctl restart isc-dhcp-server
   The service should already be configured to start automatically. If it does not, use the `systemctl` command to enable the service.

References