Setting up DHCP

When a system boots from the network, the first point for getting configuration information is the DHCP server. This means that we have to add a few lines to the DHCP server configuration to make it point to the Vinegar server.

In this example, we are going to assume that we use the ISC DHCP server. We have to add the following lines to the server’s configuration file:

# Options used for PXE boot
option architecture-type code 93 = unsigned integer 16;

# PXE boot
class "pxeclients" {
  match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
  next-server 192.2.0.99;
  if option architecture-type = 00:00 {
    filename "/grub/i386-pc/core.0";
  } else if option architecture-type = 00:06 {
    filename "/grub/i386-efi/core.efi";
  } else if option architecture-type = 00:07 {
    filename "/grub/x86_64-efi/shimx64.efi";
  }
}

The first part (defining the architecture-type option) goes into the global part of the configuration. The architecture-type simply is an alias that we define so that we can easily refer to DHCP option 93.

The second part can appear in the global part of the configuration, but it can also appear inside a group or subnet definition. This part matches any client that identifies itself as a PXE client (through the vendor-class-identifier option) and makes the IP address of the boot server (the server running Vinegar, 192.2.0.99 in this example) known to the client. It also tells the client the path of the boot loader on the boot (TFTP) server. The path depends on the client architecture because we need different versions of the boot loader for PC BIOS, UEFI 32 bit, and UEFI 64 bit systems.

If you are using a different kind of DHCP server, you have to refer to its documentation in order to find out how to set the IP address of the boot server and the architecture-dependent path to the boot loader.

If you cannot modify the configuration of an existing DHCP server, you might want to consider using [dnsmasq](https://thekelleys.org.uk/dnsmasq/doc.html). dnsmasq can operator in proxyDHCP mode, meaning that it will be able to give information about the boot server to PXE clients without interfering with the operation of the regular DHCP server. Please refer to the dnsmasq documentation in order to learn how to configure proxyDHCP mode.

We are going to set up the boot loader (GRUB 2) in the next section.