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How to network boot a Pi 4.md

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How to network boot a Pi 4

Prepare the client board

sudo apt update

To find the Ethernet MAC address:

ethtool -P eth0

e.g. dc:a6:32:03:22:20

To find the serial number:

grep Serial /proc/cpuinfo | cut -d ' ' -f 2 | cut -c 8-16

e.g. 037b65dae

You can also find the serial number on the boot screen. Boot the Pi without a micro SD card to see the boot screen and the information.

sudo raspi-config

Set the boot order

Within raspi-config, choose Advanced Options, then Boot Order, then Network Boot. You must then reboot the device for the change to the boot order to be programmed into the bootloader EEPROM.

YOU NEED TO REBOOT BACK INTO RASPBERRY PI OS! DON'T JUST SHUTDOWN

Once the Pi has rebooted, check that the boot order is now 0xf21:

vcgencmd bootloader_config

i.e. try SD first, followed by NETWORK then repeat

Optionally check the PXE boot messages.

On a different Pi, on the same network:

sudo tcpdump -i eth0 port bootpc | grep dc:a6

Prepare the server board

Install the packages needed

sudo apt update
sudo apt install -y nfs-kernel-server dnsmasq unzip nmap kpartx rsync

Your server needs to have a fixed IP address.

Note: The offical way to do this is using systemd and to create two files 10-eth0.netdev and a 11-eth0.network. Using this method didn't work as expecgted for me and the PXE boot messages where not getting to Dnsmasq. Some more debugging is needed. So instead I use the old method of /etc/network/interfaces

cat << EOF | sudo tee /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 192.168.1.45
        netmask 255.255.255.0
        gateway 192.168.1.1

source /etc/network/interfaces.d/*
EOF

Change 192.168.1.45 etc to fit your network setup.

Create the root file system that will be served over NFS

The client Raspberry Pi will need a root file system to boot from: we will use a copy of the server’s root filesystem and place it in /nfs/ where is the board's serial number without the leading zeros, e.g. 37b65dae

SERIALNUM="37b65dae"
sudo mkdir -p /nfs/$SERIALNUM
sudo rsync -xa --progress --exclude /nfs / /nfs/$SERIALNUM

Delete SSH keys and enable the ssh server

SERIALNUM="37b65dae"
cd /nfs/$SERIALNUM
sudo mount --bind /dev dev
sudo mount --bind /sys sys
sudo mount --bind /proc proc
sudo chroot . rm -f /etc/ssh/ssh_host_*
sudo chroot . dpkg-reconfigure openssh-server
sudo chroot . systemctl enable ssh
sleep 1
sudo umount dev sys proc
sudo touch boot/ssh

Configure /etc/fstab for the client

SERIALNUM="37b65dae"
echo | sudo tee /nfs/$SERIALNUM/etc/fstab
echo "proc /proc proc defaults 0 0" | sudo tee -a /nfs/$SERIALNUM/etc/fstab
echo "192.168.1.45:/tftpboot /boot nfs defaults,vers=4.1,proto=tcp 0 0" | sudo tee -a /nfs/$SERIALNUM/etc/fstab

You MUST change the serial number to that of your board, and use the correct IP address of the server (e.g. 192.168.1.45)

Export the root file system created earlier, and the TFTP boot folder.

SERIALNUM="37b65dae"      
echo "/nfs/$SERIALNUM *(rw,sync,no_subtree_check,no_root_squash)" | sudo tee -a /etc/exports
echo "/tftpboot *(rw,sync,no_subtree_check,no_root_squash)" | sudo tee -a /etc/exports

You MUST change the serial number to that of your board

TFTP

SERIALNUM="37b65dae"
sudo mkdir -p /tftpboot/$SERIALNUM
sudo chmod 777 /tftpboot
sudo cp -r /boot/* /tftpboot/$SERIALNUM
sudo cp /boot/bootcode.bin /tftpboot/

Write dnsmasq.conf

cat << EOF | sudo tee /etc/dnsmasq.conf
port=0
dhcp-range=$BRD,proxy
bind-interfaces
log-dhcp
enable-tftp
log-facility=/var/log/dnsmasq
tftp-root=/tftpboot
pxe-service=0,"Raspberry Pi Boot"
EOF

Configure cmdline.txt

SERIALNUM="37b65dae"
echo "console=serial0,115200 console=tty1 root=/dev/nfs nfsroot=192.168.1.45:/nfs/$SERIALNUM,vers=4.1,proto=tcp rw ip=dhcp rootwait" | sudo tee /tftpboot/$SERIALNUM/cmdline.txt
sudo chmod 777 /tftpboot/base/cmdline.txt

You MUST change the serial number to that of your board, and use the correct IP address of the server (e.g. 192.168.1.45)

Restart all the services

sudo systemctl enable dnsmasq
sudo systemctl restart dnsmasq
sudo systemctl enable rpcbind
sudo systemctl restart rpcbind
sudo systemctl enable nfs-kernel-server
sudo systemctl restart nfs-kernel-server

Other resources

My shell scripts to automate some of this process:

Other articles that could be useful