Ubuntu (Focal) PXE Boot with autoinstall

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After N VMs deep in my homelab and delays upon delays (read: procrastination), I’ve finally gotten around to setting up my compute provisioning workflow to do PXE boot and autoinstall. Goodbye install UI, you will not be missed.

Note: I’m running on Proxmox and (virtual) pfSense but that shouldn’t affect much of the setup.

Setup

! Most, if not all, of the commands to be run must be root

TFTP and HTTP Server

  • Install the TFTP and HTTP server via:
apt-get -y install tftpd-hpa apache2
mkdir /tftp
chown tftp:tftp /tftp
  • Edit /etc/default/tftpd-hpa with the following:
# /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/tftp"
TFTP_ADDRESS=":69"
TFTP_OPTIONS="--secure"

then

systemctl restart tftpd-hpa
  • Create /etc/apache2/conf-available/tftp.conf with:
<Directory /tftp>
    Options +FollowSymLinks +Indexes
    Require all granted
</Directory>
Alias /tftp /tftp

then

a2enconf tftp
systemctl restart apache2

BIOS Boot

  • Download the latest .iso and extract the kernel and initrd by:
wget https://releases.ubuntu.com/20.04.3/ubuntu-20.04.3-live-server-amd64.iso -O /tftp/ubuntu-20.04.3-live-server-amd64.iso
mount /tftp/ubuntu-20.04.3-live-server-amd64.iso /mnt/
cp /mnt/casper/{vmlinuz,initrd} /tftp/
umount  /mnt
  • Copy over the bootloader to the tftp directory by:
wget http://archive.ubuntu.com/ubuntu/dists/focal/main/installer-amd64/current/legacy-images/netboot/ubuntu-installer/amd64/pxelinux.0 -O /tftp/pxelinux.0
  • Install syslinux via:
apt-get -y install syslinux-common

then

cp /usr/lib/syslinux/modules/bios/{ldlinux.c32,libcom32.c32,libutil.c32,vesamenu.c32} /tftp
  • Create /tftp/pxelinux.cfg/default file with:
DEFAULT vesamenu.c32
TIMEOUT 200
ONTIMEOUT ubuntu-focal-autoinstall
PROMPT 0
NOESCAPE 1

LABEL ubuntu-focal-autoinstall
        MENU label Install Ubuntu Focal - autoinstall
        KERNEL vmlinuz
        INITRD initrd
        APPEND root=/dev/ram0 ramdisk_size=1500000 ip=dhcp url=http://<SERVER-IP>/tftp/ubuntu-20.04.3-live-server-amd64.iso autoinstall ds=nocloud-net;s=http://<SERVER-IP>/tftp/cloud-init-bios/ cloud-config-url=http://<SERVER-IP>/tftp/cloud-init-bios/meta-data

LABEL ubuntu-focal-install
        MENU label Install Ubuntu Focal
        KERNEL vmlinuz
        INITRD initrd
        APPEND root=/dev/ram0 ramdisk_size=1500000 ip=dhcp url=http://<SERVER-IP>/tftp/ubuntu-20.04.3-live-server-amd64.iso

Where:

<SERVER-IP> - IP of the TFTP server

“autoinstall” Config

  • Create /tftp/cloud-init-bios/user-data with (password is ubuntu):
#cloud-config
autoinstall:
  version: 1
  identity:
    hostname: ubuntu-server
    password: "$6$exDY1mhS4KUYCE/2$zmn9ToZwTKLhCw.b4/b.ZRTIZM30JZ4QrOQ2aOXJ8yk96xpcCof0kxKwuX1kqLG/ygbJ1f8wxED22bTL4F46P0"
    username: ubuntu

More options can be found in the reference guide.

  • Run touch /tftp/cloud-init-bios/meta-data

DHCP Update

In my case, I’m running pfSense so I had to update the DHCP server with:

Testing in Proxmox

To test if everything checks out, simply create a VM with no OS media. Network boot is already included in the boot order (last).

Gotchas

Minimum VM memory should be atleast 2GB in order for the installation to succeed.

References