Auto reconnect to wifi when lost connection

Before you start, make sure ip command is available on your system. In modern Linux distributions, ip replaces older ifconfig command. If net-tools package (that includes ifconfig) is not installed and you prefer using it, you can install it via sudo apt-get install net-tools.

Create script file

Use touch /home/pi/wifi-reconnect.sh to create a shell script file, with the following content:

#!/bin/bash

SSID=$(/sbin/iwgetid --raw)

if [ -z "$SSID" ]; then
    echo "`date -Is` WiFi interface is down, trying to reconnect" >> /home/pi/wifi-log.txt
    if command -v /sbin/ip &> /dev/null; then
        /sbin/ip link set wlan0 down
        sleep 10
        /sbin/ip link set wlan0 up
    elif command -v sudo ifconfig &> /dev/null; then
        sudo ifconfig wlan0 down
        sleep 10
        sudo ifconfig wlan0 up
    else
        echo "`date -Is` Failed to reconnect: neither /sbin/ip nor ifconfig commands are available" >> /home/pi/wifi-log.txt
    fi
fi

echo 'WiFi check finished'

Or you can also use the following command to download the script.

sudo wget https://raw.github.com/carry0987/Raspberry-Pi-Repo/master/Auto-WiFi-Reconnect/wifi-reconnect.sh

Note:

This script uses /sbin/ip command for disabling and enabling the wlan interface. This is a more modern approach compared to using ifconfig and is the preferred way in newer Linux distributions.

Make new file executable

sudo chmod +x /home/pi/wifi-reconnect.sh

Install cron

sudo apt-get install cron

Edit crontab

Use sudo vim /etc/crontab to edit crontab

By putting the following content at the end of the file:

* * * * * root /home/pi/wifi-reconnect.sh

Test it by disconnecting from WiFi:

/sbin/ip link set wlan0 down

The script should reestablish the connection within 1 minute.

Check log file

After the RPi reestablishes the connection, reconnect to the RPi and check the log file:
cat /home/pi/wifi-log.txt

For anyone struggling with this on raspios (lite, bookworm, 2024), using the provided wifi utilities (NetworkManager via raspi-config or the official rpi image writer), I found that the default connection.autoconnect-retries property is set to "-1", which apparently means it will only try 4 times. Setting it to "0" should make it try to reconnect forever. I have configured this but have yet to have enough time pass to say whether this is the fix, but we'll see. It's pretty absurd to have to rely on a script for such an assumed default behavior. The nmcli connection modify command does survive reboots.

nmcli connection modify preconfigured connection.autoconnect-retries 0
nmcli con show preconfigured
connection.autoconnect-retries: 0 (forever)

carry0987/RPi3-Auto-WiFi.md