<glacius:metadata>

    <title>WiFi Reconnection Script</title>

    <description>Little script to automatically reconnect to wifi, e.g. on a Raspberry Pi</description>

    <category>Code snippets</category>

    <category>Programming</category>

    <category>Bash</category>

</glacius:metadata>

<p>

    I recently upgraded my magic mirror from a 1st gen Raspberry Pi B to a Raspberry Pi 4.

    The RPi4 has a builtin WiFi adapter so I don't need the dongle. I thought it would be

    more stable, but so far not so much. It can't connect to my 2.4GHz SSID but kinda

    connects to the 5GHz SSID. However, it periodically refuses to reconnect. And since

    the Pi is locked inside a frame, duct-taped to the back of a monitor, it's not easy

    to rip it off the wall to troubleshoot.

</p>

<p>

    Normally what I would do is just unplug and plug it back in to make it reconnect, but

    that only seemed like a reasonable thing to do on a Pi from 2012, but not one from this

    decade. So I wrote this cron script that kind of works.

</p>

<p>

    Basically it uses the 

    <a href="https://www.networkmanager.dev/docs/api/latest/nmcli.html">NetworkManager CLI utility</a> 

    to see if the WiFi is connected,

    and if not, it cycles the radio off and then on. In the event that this doesn't work

    for 15 minutes (900 seconds), it just reboots the whole machine. I'm tired of trying

    to debug this nonsense so I'm taking a scorched Earth approach now.

</p>

<glacius:code lang="bash"><![CDATA[

#!/bin/bash

tempFile=/tmp/wifi-reconnect

if [[ ! -f "${tempFile}" ]]; then

	date +%s > "${tempFile}"

fi

if ! nmcli connection show --active | grep wifi > /dev/null; then

	lastConnected=$(cat "${tempFile}")

	threshold=900

	if [[ -n "${lastConnected}" && $(( lastConnected + threshold )) -lt $(date +%s) ]]; then

		echo "$(date) not connected, haven't connected for ${threshold}s (last: ${lastConnected}), rebooting..."

		/usr/sbin/shutdown -r now

		exit

	fi

	echo "$(date) not connected, cycling wifi radio..."

	nmcli radio wifi off

	nmcli radio wifi on

else

	echo "$(date) connected"

	date +%s > "${tempFile}"

fi

]]></glacius:code>

<p>

    This runs every minute from a cron job in <code>/etc/cron.d/wifi-reconnect</code>:

</p>

<glacius:code lang="cron"><![CDATA[* * * * * root /path/to/script/wifi-reconnect.sh >> /var/log/wifi-reconnect.log 2>&1

]]></glacius:code>

<p>

    The log file looks like this:

</p>

<glacius:code lang="plaintext"><![CDATA[Sun 14 Apr 09:29:01 PDT 2024 connected

Sun 14 Apr 09:30:01 PDT 2024 connected

Sun 14 Apr 09:31:01 PDT 2024 connected

Sun 14 Apr 09:32:01 PDT 2024 connected

Sun 14 Apr 09:33:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:34:01 PDT 2024 connected

Sun 14 Apr 09:35:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:36:01 PDT 2024 connected

Sun 14 Apr 09:37:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:38:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:39:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:40:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:41:02 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:42:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:43:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:44:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:45:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:46:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:47:02 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:48:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:49:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:50:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:51:01 PDT 2024 not connected, cycling wifi radio...

Sun 14 Apr 09:52:01 PDT 2024 not connected, haven't connected for 900s (last: 1713112561), rebooting...

Sun 14 Apr 09:53:27 PDT 2024 connected

Sun 14 Apr 09:54:01 PDT 2024 connected

Sun 14 Apr 09:55:01 PDT 2024 connected

Sun 14 Apr 09:56:01 PDT 2024 connected

]]></glacius:code>