Raspberry Pi 3B+ Auto reconnect to wifi when lost connect

RPi3-Auto-WiFi.md

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

I found that I had to replace this part of the shell script, otherwise, it appears to work well...
TL;DR

Thans for your feedback!

The issue you encountered might be due to the net-tools package, which includes the ifconfig command, not being installed on your system. Your suggestion to replace it with /sbin/ip not only makes the script more aligned with current best practices (as ifconfig has been deprecated in favor of the ip command in most Linux distributions) but also ensures better compatibility with the latest versions of Pi OS Lite.

Considering that the ip command provides a more modern and universal interface for network management and is a standard part of many Linux systems, I will update the script to use /sbin/ip. Regarding the net-tools, I will add a note to the script's documentation to help others who might face the same problem.

Thanks again for your thorough feedback and suggestion. It's precisely contributions like yours that help improve the project for everyone :)

Reeealy cool script bro... Thanks a lot

Reeealy cool script bro... Thanks a lot

Thanks :)

My Pi is pretty much at the edge of the wifi range. It works for a while but the loses the connection after a day or two.
The script tries to reconnect but fails to do so.
Is there any way to find out why, because after a reboot it comes right up.

@krummrey I had similar issues. TLDR: I changed the script to reboot the Pi, and that works as you say.

I ended up rewriting the script, in Python, so it is also run as a cron job. The script then pings a user defined DNS server, if it can't reach the server it reboots the Pi and then once the Pi is rebooted when the script next runs it emails me to say it's rebooted because of "loss of internet connection".
As I run Flightaware the script also checks the status of Dump1090 and if that reports a failure the Pi is rebooted as well, this time in the email I get the log with Dump1090's status attached.

Solved my problem, Pi is right on the edge of wifi range and this worked perfectly. Cheers

Solved my problem, Pi is right on the edge of wifi range and this worked perfectly. Cheers

I'm glad this script helped you, cheers~

You can also check if your Pi is using full power with iwconfig

_Tx-Power Gives you the maximum transmission power
and Power Managementf is telling you whether it's trying to save power by lowering the transmission power

If your output has different values, try to set them like this
sudo nano /etc/rc.local and insert iw dev wlan0 set power_save off to turn power saving off

sudo nano /etc/network/interfaces and insert

source /etc/network/interfaces.d/*
post-up iwconfig wlan0 txpower 20
wireless-power off

20 db is the maaximum value a pi can legally transmit at within the EU. The maximum the pi can send at is 31.

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)