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RPI-NetBoot

Repository used for managing, configuring and booting Raspberry PI's via the network

First we use the inventory.json file as the inventory for all PI's.

The serial number from each PI is used as the key when a PI check if it's managed by the repository or not. If the check turns out to be true, then it will look under the config section. The hostname will then be given and a possible purpose for that specific PI.

"e51b1483": {
    "model": "Raspberry Pi 3 Model B Plus Rev 1.3",
    "serial": "e51b1483",
    "wired_mac": "b8:27:eb:1b:14:83",
    "wireless_mac": "be:f0:4a:14:af:0a",
    "config": {
        "hostname": "e51b1483",
        "purpose": "ml_screen",
        "ml_screen": {
            "id": 1
        }
    }
}

NOTE: The "value" of the "purpose" key, will ALWAYS be a new key!

Raspberry PI server setup

But before the PI will be able to check if it is managed, it needs to be booted. Therefore we need three diffierent services on the network:

  • DHCP server which will hand out the following options:
    • next-server of the TFTP server e.g. 172.20.60.50
    • option tftp-server-name (66) of the TFTP server e.g. "172.20.60.50"
  • TFTP server which will store the bootfiles for the PI's (including bootcode.bin)
  • NFS server to serve the PI which it own root filesystem / and optional a /boot mount as well

Those services can be hosted on the same server, at least the TFTP and NFS properly should be hosted on the same machine, so the /boot target will be easy to expose for the PI.

I have installed all services on the same server based on the newest Debian net-install :

$ sudo apt install isc-dhcp-server tftpd-hpa nfs-kernel-server

isc-dhcp-server configuration

We need to define the interface where the dhcp server should listen, otherwise it will not start. That specific configuration is defined in /etc/default/isc-dhcp-server and change the INTERFACESv4 to the correct interface

INTERFACESv4="ens33"
#INTERFACESv6=""

After thats done we need to change actual dhcp configuration in /etc/dhcp/dhcpd.conf

NOTE: If the DHCP server is located on a different subnet, than where the PI's is located we need to define the layer2 subnet for the server as well. Otherwise the DHCP will refuse to start ...

The definition for the local layer2 subnet are shown here, it will not hand any addresses out to clients.

subnet 172.20.60.0 netmask 255.255.255.0 {
}

This is the configuration for the subnet where the PI's are located and will receive DHCP addresses and try to PXE boot from

subnet 172.20.20.0 netmask 255.255.255.0 {
  range 172.20.20.101 172.20.20.254;
  option domain-name-servers 1.1.1.1;
  option domain-name "hs-network.dk";
  option routers 172.20.20.1;
  option broadcast-address 172.20.20.255;
  default-lease-time 600;
  max-lease-time 7200;
  next-server 172.20.60.50;
  option tftp-server-name "172.20.60.50";
}

We can also define a static lease for the PI, so it always will recieve the same DHCP address. Thats quite nice for management.

NB: This should be built into the inventory, so a bash script scheduled with crontab can create these fixed addresses

host pi-ec6be72b {
  hardware ethernet b8:27:eb:6b:e7:2b;
  fixed-address 172.20.20.101;
  option host-name "ec6be72b";
}

tftp-hpa configuration

The configuration for the TFTP server is much more simple than the DHCP In order to configure the service, we need to take a look at /etc/default/tftpd-hpa. TFTP_DIRECTORY need to be configured to the decired directory and --verbose should be added to ``

# /etc/default/tftpd-hpa

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

nfs-kernel-server configuration

Last but not least we need to configure the NFS server, which will be the one handling all the storage for all PI's All configuration are done under /etc/exports which defines the targets, we are using NFSv3. For each PI there needs to at least two shares, one for the root filesystem and one for the /boot filesystem. The root filesytems are located under the nfs folder and the /boot filesystems are located under the tftp folder

NB: This should also be integrated with the inventory, so there will be a bash script that will create and update all the NFS targets. It should be scheduled via crontab.

/srv/rpi/nfs/ec6be72b/ml_screen *(rw,sync,insecure,no_subtree_check,no_root_squash)
/srv/rpi/tftp/ec6be72b *(rw,sync,insecure,no_subtree_check,no_root_squash)

Raspberry PI configuration

Every PI needs some aditional configuration in order to be able to boot of the Network

This is table shows the different models, each model have different requirements in order to be able to boot

Raspberry Pi model Able to network boot
Raspberry Pi 1 Requires a FAT32 SD-card with bootcode.bin
Raspberry Pi 2 Requires a FAT32 SD-card with bootcode.bin
Raspberry Pi 3B Requires a FAT32 SD-card with bootcode.bin
Raspberry Pi 3B+ Working out of box
Raspberry Pi 4 Needs a new EEPROM bootloader

Raspberry Pi Model 1, 2 and 3B

For those models there are some steps in order to boot off the network They all need to boot from the USB which includes the PXE boot

Append program_usb_boot_mode=1 to `/boot/config.txt``

echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt

Reboot the PI and check if it worked as it should with vcgencmd otp_dump | grep 17:

pi@raspberrypi:~ $ vcgencmd otp_dump | grep 17:
17:3020000a

The output should say 3020000a then it has worked

All three models need a FAT32 formated SD-card inserted with bootcode.bin

Raspberry Pi Model 3B+

This model should work out of the box, but otherwise do the same as Model 1, 2 and 3B. But it doesn't need a SD-card.

Raspberry Pi Model 4

For the Raspberry Pi 4 it needs a need EEPROM bootloader. It can be installed via the Raspberry Pi Imager which can be downloaded from the Official Raspberry Pi website

Individual images for different purposes

We have some different images for the different purposes in the inventory file

Configuration of ML_SCREEN

Installed packages:

  • xserver-xorg
  • x11-xserver-utils
  • xinit (I think this can be removed)
  • feh
  • openbox
  • lightdm-login-greeter (maybe)
pi@e51b1483:~ $ cat .xserverrc
#!/bin/sh

exec /usr/bin/X -listen tcp "$@"

pi@e51b1483:~ $ cat .xinitrc
#!/bin/sh

xsetroot -solid white &
sh ~/.fehbg &
openbox --config-file /home/pi/.config/openbox/bare.xml

Nice things which we need to use in scripts

Grep the Model from a RPI

pi@rpi-master:~ $ cat /proc/cpuinfo | grep Model | cut -d ':' -f 2 | sed -e 's/^[ \t]*//'
Raspberry Pi 3 Model B Plus Rev 1.3

Grep the S/N from a RPI

pi@rpi-master:~ $ cat /proc/cpuinfo | grep Serial | cut -d ':' -f 2 | sed -e 's/^[ \t]*//' | sed -E 's/.*(.{8})$/\1/'
e51b1483

License

MIT