Setting Up a Wi-Fi Hotspot on Boot for Your Robot

TL;DR: Three small pieces give your robot a self-hosted Wi-Fi network that survives reboots: a script that brings up an nmcli hotspot, a chmod 600 credentials file it reads, and a systemd oneshot service that runs it at boot. Recipe below, tested on our Fetch robot (Ubuntu 18.04).

Index

• Index
  • Why Create a Wi-Fi Hotspot on Boot?
  • Prerequisites
  • Step 1: Create the Hotspot Script
  • Step 2: Create a Credentials File
  • Step 3: Create a Systemd Service
  • Step 4: Verify Hotspot on Boot
  • Step 5: Optional – Add Status Check to ~/.bashrc
  • Troubleshooting

Why Create a Wi-Fi Hotspot on Boot?

In robotics, self-hosted networks can be critical for:

• Connecting remote controllers or operator devices.
• Transmitting real-time data streams (e.g., images, depth, or control commands).
• Enabling peer-to-peer communication in isolated environments.

Let’s configure a Wi-Fi hotspot to start automatically whenever your robot boots up. 📡🤖✨

Prerequisites

• A Linux-based system (tested on Ubuntu). Our Fetch robot has Ubuntu 18.04 installed.
• NetworkManager installed (pre-installed on Ubuntu desktop editions).
• A compatible Wi-Fi adapter connected to the robot.
• Root access to the system.

📋 Ensure these are set up before proceeding!

Step 1: Create the Hotspot Script

Let’s have a directory related to this setting:

# try setting absolute path
export WIFI_ADAP_ROOT_DIR=/home/fetch/wifi-adapter-settings
mkdir -p $WIFI_ADAP_ROOT_DIR
cd $WIFI_ADAP_ROOT_DIR

We’ll use a Bash script to configure and start the hotspot. Create the file start_hotspot.sh:

#!/bin/bash

# Disable the firewall
ufw disable

echo "Firewall stopped and disabled on system startup"

# Wait for 2 seconds
sleep 2

# Read credentials and create hotspot
# Use the absolute path here: systemd runs this script with a clean
# environment, so $WIFI_ADAP_ROOT_DIR will NOT be set at boot.
CREDS_FILE=/home/fetch/wifi-adapter-settings/hotspot_creds.cfg
source $CREDS_FILE

# Create the hotspot
nmcli device wifi hotspot ifname alpha_wifi_adap ssid "$SSID" password "$PASSWORD" band a channel 149

Explanation of the Script:

• Disable the firewall: Ensures no network traffic is blocked (this is fine on an isolated lab robot — adjust for secure setups).
• Wait for 2 seconds: Adds a buffer to ensure system services are up.
• Source credentials: Reads the hotspot name (SSID) and password from hotspot_creds.cfg. Use the absolute path — when systemd runs this script at boot, shell environment variables like $WIFI_ADAP_ROOT_DIR are not set.
• Set up the hotspot: Uses nmcli to configure and start the hotspot.

Save this script to $WIFI_ADAP_ROOT_DIR/start_hotspot.sh and make it executable:

chmod +x $WIFI_ADAP_ROOT_DIR/start_hotspot.sh

Step 2: Create a Credentials File

Store your hotspot credentials in a secure configuration file:

nano $WIFI_ADAP_ROOT_DIR/hotspot_creds.cfg

Add the following content:

SSID="your_hotspot_name"
PASSWORD="your_secure_password"

Make sure the credentials file is readable only by the owner:

chmod 600 $WIFI_ADAP_ROOT_DIR/hotspot_creds.cfg

🛡️ This keeps your credentials secure!

Step 3: Create a Systemd Service

To ensure the hotspot script runs on every boot, create a systemd service file:

sudo nano /etc/systemd/system/start_hotspot.service

Add the following content:

[Unit]
Description=Start Hotspot Script on Boot
After=network.target

[Service]
Type=oneshot
ExecStart=/bin/bash /home/fetch/wifi-adapter-settings/start_hotspot.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Explanation of the Service File:

• After=network.target: Ensures the service starts after network services are ready.
• ExecStart: Runs the hotspot script. NOTE: Keep the absolute path of the script.
• RemainAfterExit: Keeps the service active after execution.

Enable the service:

sudo systemctl enable start_hotspot.service

Test the service by starting it manually:

sudo systemctl start start_hotspot.service
sudo systemctl status start_hotspot.service

If successful, the hotspot should start without errors. 🚀✨

Step 4: Verify Hotspot on Boot

To confirm the hotspot starts correctly after reboot:

• Reboot your system:

  sudo reboot
  

• Once the system boots up, check the hotspot status:

  sudo systemctl status start_hotspot.service
  

• You can also use the nmcli command to verify:

  nmcli dev wifi
  

✅ This ensures everything is working smoothly! 🌟

Step 5: Optional – Add Status Check to ~/.bashrc

For convenience, add a status check to your ~/.bashrc file. This will display the hotspot’s status whenever you open a terminal:

# Check Hotspot Status, use absolute path
CREDS_FILE=/home/fetch/wifi-adapter-settings/hotspot_creds.cfg
if [ -f $CREDS_FILE ]; then
    source $CREDS_FILE
    if nmcli dev wifi | grep -q "$SSID"; then
        ip_address=$(ip addr show alpha_wifi_adap | grep 'inet ' | awk '{print $2}' | cut -d/ -f1)
        echo "Hotspot '$SSID' is LIVE."
        echo -e "- IP: $ip_address
- Password: $PASSWORD"
    else
        echo "Hotspot '$SSID' is NOT ACTIVE."
    fi
else
    echo "Hotspot credentials file not found."
fi

Troubleshooting

• Error: Not authorized to control network:
  • Ensure the script is executed with root privileges.
• Error: either ‘dev’ is duplicate or ‘iwlist’ is garbage:
  • Verify the hotspot interface name (alpha_wifi_adap).
  • Double-check the hotspot script syntax.
• Hotspot not starting on boot:
  • Check the service logs:

    sudo journalctl -u start_hotspot.service
    

🛠️ Be ready to debug as needed! 🧩

Feel free to reach out in case you have a query. You are always welcome. You can find me on X at @jishnu_jaykumar.