Pxe boot (BIOS & UEFI)

2022-02-25 4 min read

This post is not meant to be a complete HOWTO article on setting up a complete network boot environment, but more of a reminder for myself as to the things I had to do to get this working on my network. If this winds up helping someone else then that is just the “icing on the cake” as they say.

I wanted to learn more about PXE booting before getting started with Ubuntu MASS. I did this to have a better understanding of the underlying technologies. My ultimate goal is to autoinstall Ubuntu Server on Bare Metal (HP-T620’s) for my home lab Kubernetes cluster Ansbile deployment. I wanted a way to auto install everything from bare metal to the K8’s pods so I could “refresh” the cluster at anytime after I messed something up while learning clustered K8s.

I thought about using one of my many Raspberry Pi’s as my PXE boot server, but in the end I had already built a small HP EliteDesk running Ubuntu 20.04 to mirror the Ubuntu package repositories so that I could cut down on my internet data usage, so I used that machine instead.

On my network, the PXE boot functions are split between two machines. The first is my router that runs Pfsense and the second is the apt-mirror machine I mentioned earlier.

Hosts and function:

pfsense : DHCP, DNS
apt-mirror: TFTP, HTTP

TFTP config

Prep the system

tftpd-hpa is the tftp service, pxelinux is a bootloader member of the syslinux family, and is built for the PXE environment, the syslinux-efi package contains libraries needed to support EFI clients.

# become root on your TFTP server
sudo su 

apt install syslinux-common syslinux-efi pxelinux tftpd-hpa 

mkdir -p /tftpboot/{bios,efi32,efi64,boot,iso,pxelinux.cfg}
cd /tftpboot

ln -rs pxelinux.cfg bios  && ln -rs pxelinux.cfg efi32  && ln -rs pxelinux.cfg efi64
ln -rs boot bios && ln -rs boot efi32 && ln -rs boot efi64


# BIOS files
cp /usr/lib/syslinux/modules/bios/{ldlinux,vesamenu,libcom32,libutil}.c32 /tftpboot/bios
cp /usr/lib/PXELINUX/pxelinux.0  /tftpboot/bios

# UEFI-32 files
cp /usr/lib/syslinux/modules/efi32/ldlinux.e32  /tftpboot/efi32
cp /usr/lib/syslinux/modules/efi32/{vesamenu,libcom32,libutil}.c32  /tftpboot/efi32
cp /usr/lib/SYSLINUX.EFI/efi32/syslinux.efi  /tftpboot/efi32

# UEFI-64 files
cp /usr/lib/syslinux/modules/efi64/ldlinux.e64  /tftpboot/efi64
cp /usr/lib/syslinux/modules/efi64/{vesamenu,libcom32,libutil}.c32  /tftpboot/efi64
cp /usr/lib/SYSLINUX.EFI/efi64/syslinux.efi  /tftpboot/efi64

# confirm port 69 is ALLOWED on local firewall
ufw status
# if ufw (micro firewall) is active and  69 is not allowed then:
# ufw allow 69

# tree view of tftpboot folder contents:
tftpboot
├── bios
│   ├── codewall.png
│   ├── ldlinux.c32
│   ├── libcom32.c32
│   ├── libutil.c32
│   ├── pxelinux.0
│   ├── pxelinux.cfg -> ../pxelinux.cfg
│   └── vesamenu.c32
├── boot
│   ├── ...
├── efi32
│   ├── codewall.png
│   ├── ldlinux.e32
│   ├── libcom32.c32
│   ├── libutil.c32
│   ├── pxelinux.cfg -> ../pxelinux.cfg
│   ├── syslinux.efi
│   └── vesamenu.c32
├── efi64
│   ├── codewall.png
│   ├── grub.cfg
│   ├── ldlinux.e64
│   ├── libcom32.c32
│   ├── libutil.c32
│   ├── pxelinux.cfg -> ../pxelinux.cfg
│   ├── syslinux.efi
│   └── vesamenu.c32
├── iso
│   ├── ...
└── pxelinux.cfg
    └── default

NOTE: I have set a menu background “codewall.png” that I modified 3 copies of. Each image has been edited to show one of “BIOS, EFI-32, EFI-64” as part of the background, so that I know which boot dir was chosen by DHCP during the PXE boot process. (Just because I wanted to know how each system booted.)

TFTPD config

sudo nano /etc/default/tftpd-hpa

# FILE: /etc/default/tftpd-hpa
TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/tftpboot"
TFTP_ADDRESS="0.0.0.0:69"
TFTP_OPTIONS="--secure"

sudo systemctl restart tftpd-hpa

HTTP config

install Apache HTTP server

sudo apt install apache2

edit the config file

nano /etc/apache2/sites-available/000-default.conf

# add this to the VirtualHost config:

Alias "/tftp" "/tftpboot"
<Directory "/tftpboot">
	Options +Indexes
	Order allow,deny
	Allow from all
	Require all granted
</Directory>

DHCP server config

I use pfsense as the DHCP server for my network.

Pfsense TFTP config example:

From the Pfsense admin dashboard click “Services” then “DHCP Server” to configure TFTP for the network you have.

pfsense screenshot of pxe config

Ubuntu Server files

Download the ISO image

cd /tftpboot/iso

# Download the Server ISO
wget https://releases.ubuntu.com/20.04.3/ubuntu-20.04.3-live-server-amd64.iso

Prepare the boot files

cd /tftpboot
# make a directory for ubuntu boot files (kernel,etc)
mkdir boot/ubuntu2004

# mount the downloaded ISO file to /mnt
mount iso/ubuntu-20.04.3-live-server-amd64.iso /mnt
# alternately: sudo mount -o loop -t iso9660 <source.iso> <mountpoint>

# copy the boot files from ISO image to boot/ubuntu2004 
sudo cp /mnt/casper/initrd  /tftpboot/boot/ubuntu2004
sudo cp /mnt/casper/vmlinuz /tftpboot/boot/ubuntu2004

# Unmount the image:
sudo umount /mnt

Edit pxelinux config file

nano /tftpboot/pxelinux.cfg/default

# FILE: /tftpboot/pxelinux.cfg/default
UI vesamenu.c32
MENU TITLE  My Custom Net Boot Menu
MENU RESOLUTION 640 480
MENU BACKGROUND codewall.png

    LABEL Ubuntu 20.04.3 Server Manual install
        KERNEL boot/ubuntu2004/vmlinuz
        INITRD boot/ubuntu2004/initrd
        APPEND url=http://TFTP_SERVER_IP/tftp/iso/ubuntu-20.04.3-live-server-amd64.iso root=/dev/ram0 ramdisk_size=1500000 ip=dhcp cloud-config-url=/dev/null ---

    LABEL Local
        MENU LABEL Boot from local drive
        LOCALBOOT 0xffff

Done!

Now go enjoy booting Ubuntu server over the network and not needing a USB drive.

Articles that inspired me during this project: