hotspot.md

Raspberry Pi Hotspot Setup

by default, the Raspberry Pi's network management system (wpa_supplicant or NetworkManager, depending on your setup) will automatically attempt to connect to known Wi-Fi networks during boot. If you’ve configured known networks in the wpa_supplicant.conf file or using NetworkManager or raspi-config, the Pi will try to connect to these networks without requiring additional scanning logic in a script.

The key idea here is to detect whether the Pi successfully connected to any network and, if not, start the hotspot. This simplifies the script, as you don't need to handle Wi-Fi scanning yourself—just check the connection status.

Simplified Script

This script assumes the Raspberry Pi will attempt to connect to known networks on its own. It checks if the Pi is connected to a network, and if not, starts the hotspot.

#!/bin/bash

# Wi-Fi hotspot configuration
HOTSPOT_SSID="printit"
STATIC_IP="192.168.4.1"
DHCP_CONFIG="/etc/dhcpcd.conf"
HOTSPOT_CONFIG="/etc/dhcpcd_hotspot.conf"
DEFAULT_CONFIG="/etc/dhcpcd_default.conf"

function backup_default_config() {
    # Back up the original DHCP configuration if not already backed up
    if [ ! -f "$DEFAULT_CONFIG" ]; then
        echo "Backing up default DHCP configuration..."
        sudo cp "$DHCP_CONFIG" "$DEFAULT_CONFIG"
    fi
}

function configure_static_ip() {
    echo "Configuring static IP for hotspot..."
    sudo bash -c "cat > $HOTSPOT_CONFIG" <<EOL
interface wlan0
static ip_address=$STATIC_IP/24
nohook wpa_supplicant
EOL
    sudo cp "$HOTSPOT_CONFIG" "$DHCP_CONFIG"
    sudo systemctl restart dhcpcd
}

function configure_dhcp() {
    echo "Reverting to DHCP configuration..."
    if [ -f "$DEFAULT_CONFIG" ]; then
        sudo cp "$DEFAULT_CONFIG" "$DHCP_CONFIG"
        sudo systemctl restart dhcpcd
    else
        echo "Default DHCP configuration not found. Skipping..."
    fi
}

function is_connected() {
    echo "Checking Wi-Fi connection status..."
    if ip addr show wlan0 | grep -q "inet "; then
        echo "Wi-Fi is connected."
        return 0
    else
        echo "Wi-Fi is not connected."
        return 1
    fi
}

function start_hotspot() {
    echo "Starting Wi-Fi hotspot..."
    configure_static_ip

    # Stop conflicting services
    sudo systemctl stop hostapd dnsmasq

    # Configure dnsmasq
    sudo bash -c "cat > /etc/dnsmasq.conf" <<EOL
interface=wlan0
dhcp-range=192.168.4.2,192.168.4.20,255.255.255.0,24h
EOL

    # Configure hostapd for an open network
    sudo bash -c "cat > /etc/hostapd/hostapd.conf" <<EOL
interface=wlan0
driver=nl80211
ssid=$HOTSPOT_SSID
hw_mode=g
channel=7
wmm_enabled=0
auth_algs=1
ignore_broadcast_ssid=0
EOL

    sudo sed -i 's|#DAEMON_CONF=""|DAEMON_CONF="/etc/hostapd/hostapd.conf"|' /etc/default/hostapd

    # Enable NAT
    sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
    sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"
    sudo bash -c "echo 'iptables-restore < /etc/iptables.ipv4.nat' >> /etc/rc.local"

    # Restart services
    sudo systemctl restart dnsmasq
    sudo systemctl unmask hostapd
    sudo systemctl restart hostapd
    echo "Open hotspot started: SSID=$HOTSPOT_SSID"
}

function main() {
    backup_default_config

    is_connected
    if [ $? -eq 0 ]; then
        echo "Wi-Fi is connected. Reverting to DHCP configuration."
        configure_dhcp
        exit 0
    fi

    echo "Wi-Fi is not connected. Starting open hotspot..."
    start_hotspot
}

main

Steps to Set Up

1. Install Required Packages: Ensure hostapd and dnsmasq are installed:

   sudo apt update && sudo apt install -y hostapd dnsmasq

2. Save and Make the Script Executable: Save the script as /usr/local/bin/wifi_hotspot_manager.sh:

   sudo nano /usr/local/bin/wifi_hotspot_manager.sh
   chmod +x /usr/local/bin/wifi_hotspot_manager.sh

3. Run Script on Startup: Add the script to the system's startup sequence:

   sudo crontab -e

   Add the following line:

   @reboot /usr/local/bin/wifi_hotspot_manager.sh
   

4. Reboot to Test: Restart your Raspberry Pi:

   sudo reboot

How It Works

1. Default Wi-Fi Handling: The Raspberry Pi attempts to connect to known networks as per its default behavior.
2. Connection Check: The script checks if the wlan0 interface has a valid IP address.
3. Hotspot Activation: If no IP address is assigned (no connection), the script starts the hotspot.

This approach leverages the Pi's default Wi-Fi scanning behavior, simplifying the logic.