Streamlining Raspberry Pi Deployment: A Guide to Automated Netbooting

In this blog, we’ll delve into automating the netbooting process using a bash script (pxeService.sh) and an address list (addresslist.txt) to enhance the deployment and management of Raspberry Pi devices. If you haven’t already, you can catch up on the initial steps and concepts discussed here, where we laid the groundwork for this automation project.

Bash Script Overview

The pxeService.sh script is designed to automate the setup for each PXE client (Raspberry Pi device). You can look at the complete pxeService.sh script here. Here’s a breakdown of the script:

Constants and Log Paths

In this code snippet, we define constants for the script, such as the UDP port to listen on (PORT=69) and the path for logging (pxe_service_log_path="/var/log/pxeService.log"). Before running the script, it’s essential to ensure that the pxeService.log file is created in the /var/log directory. This log file will store the script’s output and any logged messages during execution.

#!/bin/bash
PORT=69
pxe_service_log_path="/var/log/pxeService.log"

Handling Error and Listening to Requests

One of the script’s critical components is the use of tcpdump. This tool plays a crucial role in real-time network monitoring. It allows the script to capture and analyse network traffic, specifically UDP requests, on a specified port ($PORT). This capability is fundamental as it enables the script to promptly detect and respond to incoming requests from PXE clients.

# Function to handle errors
handle_error() {
    local line_number="$1"
    echo "An error occurred at line $line_number" >> "$pxe_service_log_path"
    exit 1
}

# Function to process UDP packets
process_udp_packets() {
    tcpdump -l -i any -e udp port "$PORT" | while read -r line; do
        MAC=$(echo "$line" | awk '{print $6}' | tr ':' '-')
        TIME=$(date +"%Y-%m-%d %H:%M:%S")

        if grep -q "$MAC" /opt/addresslist.txt; then
            echo "$MAC already exists" >> "$pxe_service_log_path"
        else
            echo "************Executing macscript.sh for $MAC***************" >> "$pxe_service_log_path"
            echo "$MAC" >> /opt/addresslist.txt

            FILE=$(echo "$line" | grep -o -P '(?<=RRQ ")[^"]+')
            FILE=$(awk -F'/' '{print $NF}' <<< "$FILE")

            if [ "$FILE" = "start4.elf" ]; then
                echo "Time: $TIME, MAC address: $MAC, Requested file: $FILE" >> "$pxe_service_log_path"
                configure_pxe_services "$MAC" &
                echo "**********macscript execution finished for MAC $MAC**********" >> "$pxe_service_log_path"
            else
                echo "Not found" >> "$pxe_service_log_path"
            fi
        fi
    done
}

# Trap for handling errors
trap 'handle_error $LINENO' ERR

# Start processing UDP packets
process_udp_packets

Configure dnsmasq.conf

Another vital aspect is configuring dnsmasq specifically for the TFTP (Trivial File Transfer Protocol) server functionality. In this context, dnsmasq serves as the TFTP server, which is essential for transferring boot files to PXE clients during netbooting. The enable-tftp option in the configuration enables TFTP support within dnsmasq, ensuring seamless file transfer operations. Additionally, the tftp-root parameter specifies the root directory for TFTP, providing a structured environment for storing and accessing boot files required by PXE clients.

# Function to configure dnsmasq service
configure_dnsmasq_service() {
    local service_name="$1"
    local dnsmasq_conf="/etc/dnsmasq.conf"

    if [ "$service_name" == "dnsmasq" ] && systemctl is-active --quiet "dnsmasq"; then
        echo "Configuring $dnsmasq_conf..."

        read -p "Enter the interface name (e.g., bond0): " interface_name

        # Create or append to dnsmasq configuration
        cat <<EOF | sudo tee -a "$dnsmasq_conf" > /dev/null
interface=$interface_name
no-hosts
enable-tftp
tftp-root=/srv/tftp
tftp-unique-root=mac
log-facility=/var/log/dnsmasq
port=5353
EOF

        echo "Configuration has been added to $dnsmasq_conf" >> "$pxe_service_log_path"
    fi
}

Install Necessary Services

The ensure_service_installed function checks whether a specific service is installed and active. If the service is inactive, it attempts to install it using apt and then starts. If the installation and start are successful, it logs the outcome; otherwise, it logs a failure message.

# Function to ensure service is installed
ensure_service_installed() {
    local service_name="$1"

    if systemctl is-active --quiet "$service_name"; then
        echo "$service_name is already installed and active." >> "$pxe_service_log_path"
    else
        echo "Installing and starting $service_name..." >> "$pxe_service_log_path"

        sudo apt update
        sudo apt install -y "$service_name"

        if systemctl is-active --quiet "$service_name"; then
            echo "$service_name installed and started successfully." >> "$pxe_service_log_path"
            configure_dnsmasq_service "$service_name"
        else
            echo "Failed to install or start $service_name. Please check and install it manually." >> "$pxe_service_log_path"
        fi
    fi
}

Copying Boot, Root Files and Exporting the Entries to Exports

The configure_pxe_services function is responsible for setting up the necessary directories, copying boot and root files, configuring cmdline.txt and fstab files, and adding entries to the Raspberry Pi server’s exports. It performs these actions to ensure the PXE services are properly configured for a specific MAC address, effectively facilitating the netbooting process.

# Function to configure PXE services
configure_pxe_services() {
    local mac_address="$1"
    local nfs_root="/srv/nfs/$mac_address"
    local tftp_root="/srv/tftp/$mac_address"
    local nfs_exports="/etc/exports"

    # Log start of script execution
    echo "**********Configuring PXE services for $mac_address**********" >> "$pxe_service_log_path"

    # Ensure required services are installed
    ensure_service_installed "nfs-kernel-server"
    ensure_service_installed "dnsmasq"

    # Create directories for TFTP and NFS
    echo "Creating directories for $mac_address in TFTP and NFS" >> "$pxe_service_log_path"
    sudo mkdir -p "$tftp_root" "$nfs_root"

    # Copy necessary files to NFS and TFTP directories
    echo "Copying root files to NFS directory" >> "$pxe_service_log_path"
    sudo cp -a "/home/pi/userfiles/"* "$nfs_root"
    echo "Finished copying root files" >> "$pxe_service_log_path"

    echo "Copying boot files to TFTP directory" >> "$pxe_service_log_path"
    sudo cp -r "/home/pi/bootfiles/"* "$tftp_root"
    echo "Finished copying boot files" >> "$pxe_service_log_path"

    # Configure cmdline.txt for boot parameters
    echo "Configuring boot parameters in cmdline.txt" >> "$pxe_service_log_path"
    echo -e "console=serial0,115200 console=tty1 root=/dev/nfs nfsroot=192.168.XX.XX:$nfs_root rw rootwait" | sudo tee "$tftp_root/cmdline.txt" > /dev/null

    # Update fstab with NFS mount entry
    local new_fstab_content="proc            /proc           proc    defaults        0       0\n\
    PARTUUID=4e639091-02  /               ext4    defaults,noatime  0       1\n\
    192.168.XX.XX:$tftp_root /boot nfs defaults 0 0"

    echo "Updating fstab with NFS mount entry" >> "$pxe_service_log_path"
    echo -e "$new_fstab_content" | sudo tee "$nfs_root/etc/fstab" > /dev/null

    # Add NFS and TFTP entries to export file
    echo "Adding NFS export in $nfs_exports" >> "$pxe_service_log_path"
    echo "$nfs_root *(rw,sync,no_subtree_check,no_root_squash)" | sudo tee -a "$nfs_exports" > /dev/null

    echo "Adding TFTP export in $nfs_exports" >> "$pxe_service_log_path"
    echo "$tftp_root *(rw,sync,no_subtree_check,no_root_squash)" | sudo tee -a "$nfs_exports" > /dev/null

    # Reload NFS exports
    echo "Reloading NFS exports" >> "$pxe_service_log_path"
    sudo exportfs -r

    # Log completion of script execution
    echo "**********Successfully configured PXE services for $mac_address**********" >> "$pxe_service_log_path"
}

Address List Management

The addresslist.txt file serves as a record of processed MAC addresses. Before executing the setup for a new MAC address, the script checks this list to ensure it hasn’t already been configured. This prevents unnecessary duplication of efforts. Create addresslist.txt in the /opt directory. Here’s an example of how the addresslist.txt file might look:

00-11-22-33-44-55
aa-bb-cc-dd-ee-ff

Running the Script as a Daemon

To ensure continuous monitoring and execution of the pxeService.sh script, we can set it up as a daemon process using a systemd service unit file (pxeService.service). Here’s how you can create and configure the service:

Copy the pxeService.sh file to the /usr/bin directory.
Create a new file named pxeService.service in the /etc/systemd/system/ directory.
Add the following content to pxeService.service:

[Unit]
Description=PXE Service Daemon
After=network.target

[Service]
Type=simple
ExecStart=/bin/bash /usr/bin/pxeService.sh
Restart=always

[Install]
WantedBy=multi-user.target

Save the file and exit the editor, then reload systemd to read the new service unit:

sudo systemctl daemon-reload

Enable and start the pxeService.service

sudo systemctl enable pxeService.service
sudo systemctl start pxeService.service

Now, the pxeService.sh script will run as a daemon, continuously monitoring and automating the netbooting process for the new Raspberry Pi devices.

Conclusion

In this guide, we’ve automated the booting process using bash scripting. By leveraging automation and creating a daemon service, you can significantly streamline the provisioning and maintenance of Raspberry Pi devices in your network.