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This article is a step by step guide for building your own PXE boot infrastructure which can be used to boot both legacy BIOS and EFI based hardware from network. There are many articles on the Internet for building PXE boot infrastructure however I found most of them does not work for EFI based hardware. I use iPXE as the boot image and dnsmasq as DHCP & TFTP server and I found it's dead simple to setup those two software.

1. PXE Boot server (Centos 7.5) with two interfaces. Interface 'eth0' is for sysadmin to login and manage the server. Interface 'eth1' is connected to the PXE boot subnet.
2. PXE Boot subnet (10.0.0.0/24). This is an isolated network created just for booting new servers on the network. I strongly suggest to use isolated network for PXE boot to prevent it from interfering with existing DHCP servers on the network.
3. PXE Boot client. A VMware VM set to PXE boot from network.

1. Make network interface connected to PXE boot network is correctly configured

   [sysadmin@pxeboot-server ~]$ sudo ifconfig eth1 10.0.0.1 netmask 255.255.255.0 up

   if ifconfig command is not available on your machine, you can add IP address this way:

   [sysadmin@pxeboot-server ~]$ sudo ip addr add 10.0.0.1/24 dev eth1
   [sysadmin@pxeboot-server ~]$ sudo ip link set eth1 up

2. Update PXE boot server to latest version

   [sysadmin@pxeboot-server ~]$ sudo yum update -y

3. Install required packages

   [sysadmin@pxeboot-server ~]$ yum install -y ipxe-bootimgs dnsmasq 

4. Create TFTP root directory

   [sysadmin@pxeboot-server ~]$ mkdir /tftpboot

   (optional) Set the directory security label if SELinux is enforced

   [sysadmin@pxeboot-server ~]$ sudo chcon -t tftpdir_t /tftpboot

5. Copy iPXE boot images to TFTP directory

   [sysadmin@pxeboot-server ~]$ sudo cp /usr/share/ipxe/{undionly.kpxe,ipxe.efi} /tftpboot/

   undionly.kpxe is for legacy BIOS based hardware ipxe.efi is for EFI based hardware

6. Create iPXE menu directory and boot menu

   $ sudo mkdir /tftpboot/menu
   

   create a simple boot menu which drops to the iPXE shell

   sudo vi /tftpboot/menu/boot.ipxe
   

   with content :

   #!ipxe
   
   menu PXE Boot Options
   
   item shell iPXE shell
   item exit  Exit to BIOS
   
   choose --default exit --timeout 10000 option && goto ${option}
   
   :shell
   shell
   
   :exit
   exit
   

   Full iPXE command help can be found here

7. Create dnsmasq config file at /etc/dnsmasq.conf. Delete all old content before editing.

   # enable logs if required
   #log-queries
   #log-dhcp
   
   # disable DNS server
   port=0
   
   # listen on PXEBOOT vlan (vlan110) only
   listen-address=10.0.0.1
   interface=eth1
   
   # enable built-in tftp server
   enable-tftp
   tftp-root=/tftpboot
   
   
   # DHCP range 10.0.0.200 ~ 10.0.0.250
   dhcp-range=10.0.0.200,10.0.0.250,255.255.255.0,24h
   
   # Default gateway
   dhcp-option=3,10.0.0.1
   
   # Domain name - homelab.net
   dhcp-option=15,homelab.net
   
   # Broadcast address
   dhcp-option=28,10.0.0.255
   
   # Set interface MTU to 9000 bytes (jumbo frame)
   # Enable only when your network supports it
   # dhcp-option=26,9000
   
   # Tag dhcp request from iPXE
   dhcp-match=set:ipxe,175
   
   # inspect the vendor class string and tag BIOS client
   dhcp-vendorclass=BIOS,PXEClient:Arch:00000
   
   # 1st boot file - Legacy BIOS client
   dhcp-boot=tag:!ipxe,tag:BIOS,undionly.kpxe,10.1.0.1
   
   # 1st boot file - EFI client
   # at the moment all non-BIOS clients are considered
   # EFI client
   dhcp-boot=tag:!ipxe,tag:!BIOS,ipxe.efi,10.1.0.1
   
   # 2nd boot file
   dhcp-boot=tag:ipxe,menu/boot.ipxe
   

8. Open firewall rules to allow inbound DHCP and TFTP requests

   $ sudo firewall-cmd --add-service=dhcp --permanent
   $ sudo firewall-cmd --add-service=tftp --permanent
   $ sudo firewall-cmd --add-service=dns --permanent
   $ sudo firewall-cmd --reload

9. Start dnsmasq and make sure it's running

   $ sudo systemctl start dnsmasq
   $ sudo systemctl status dnsmasq
   ● dnsmasq.service - DNS caching server.
      Loaded: loaded (/usr/lib/systemd/system/dnsmasq.service; disabled; vendor preset: disabled)
      Active: active (running) since Sat 2018-06-09 12:01:23 AWST; 6min ago
    Main PID: 24141 (dnsmasq)
      CGroup: /system.slice/dnsmasq.service
              └─24141 /usr/sbin/dnsmasq -k
   

10. Now you can power on the client machine and, if the network has been configured correctly, you should see the boot process looks like this one:

click the above image to replay

In the part 1 we setup a bare bone PXE boot server using iPXE and a simple boot menu. In this section, I am going to explain how to enable network based installation for CentOS 7.

1. Install Apache web server or any web server of your choice. We are going to serve the installation media using web service.

   $ yum install -y httpd
   

2. Create media sub-directory under Apache's default document root directory and mount the CentOS 7 ISO image.

   $ sudo mkdir -p /var/www/html/media/centos7
   

   I have the CentOS 7 ISO image at /tmp/CentOS-7-x86_64-Minimal-1804.iso and I need to mount it at the mount point above

   $ sudo mount -t iso9660 -o ro,loop \
   /tmp/CentOS-7-x86_64-Minimal-1804.iso /var/www/html/media/centos7
   

3. Update host firewall and start web service

   $ sudo firewall-cmd --add-service=http --permanent
   $ sudo firewall-cmd --reload
   
   $ sudo systemctl start httpd
   

   You need to make sure Apache is running at the end of this step

   $ sudo systemctl status httpd
   ● httpd.service - The Apache HTTP Server
      Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
      Active: active (running) since Sat 2018-06-09 14:31:20 AWST; 3h 47min ago
        Docs: man:httpd(8)
              man:apachectl(8)
    Main PID: 1434 (httpd)
      Status: "Total requests: 660; Current requests/sec: 0; Current traffic:   0 B/sec"
      CGroup: /system.slice/httpd.service
              ├─1434 /usr/sbin/httpd -DFOREGROUND
              ├─1435 /usr/sbin/httpd -DFOREGROUND
              ├─1436 /usr/sbin/httpd -DFOREGROUND
              ├─1437 /usr/sbin/httpd -DFOREGROUND
              ├─1438 /usr/sbin/httpd -DFOREGROUND
              ├─1439 /usr/sbin/httpd -DFOREGROUND
              ├─1489 /usr/sbin/httpd -DFOREGROUND
              ├─1731 /usr/sbin/httpd -DFOREGROUND
              ├─1732 /usr/sbin/httpd -DFOREGROUND
              └─1878 /usr/sbin/httpd -DFOREGROUND
   

4. Add CentOS installation option to /tftpboot/menu/boot.ipxe file so it looks like this:

   #!ipxe
   
   :start
   menu PXE Boot Options
   item shell iPXE shell
   item centos7-net CentOS 7 installation
   item exit  Exit to BIOS
   
   choose --default centos7-net --timeout 10000 option && goto ${option}
   
   :shell
   shell
   
   :centos7-net
   set server_root http://10.0.0.1/media/centos7
   initrd ${server_root}/images/pxeboot/initrd.img
   kernel ${server_root}/images/pxeboot/vmlinuz inst.repo=${server_root}/ ip=dhcp ipv6.disable initrd=initrd.img inst.geoloc=0 devfs=nomount
   boot
   
   :exit
   exit
   

5. Now, reboot your client machine you should be able to see the new option install CentOS