Auto Reconnect WiFi on Raspberry Pi

October 19, 2017

My Raspberry Pi 3 Wi-Fi isn’t very reliable even after disabling power management my RPI still manages to lose connection to my Wi-Fi router and i don’t have any keyboard or screen connected to it and its not advisable to do hard reset i.e unplug the power as it may corrupt your SD card. I’m going to cover writing a short script that Auto Reconnect WiFi on Raspberry Pi to a Wi-Fi network. The script will run as cron job at around 5 minutes interval to check if the Pi has network connectivity and if it is offline, restart the wireless interface to bring it back online.

There are a few ways to determine if the Raspberry Pi has Wi-Fi network connectivity. I’ll be using ping to determine Wi-Fi connection status.

Auto Reconnecting Wi-Fi Script

First we need to determine if the Raspberry Pi is connected to the Wi-Fi network. To do this, we can ping a our Wi-Fi router if you want to test internet connectivity you can use google DNS IP address 8.8.8.8 instead but we only want to check connection to our Wi-Fi router. If Raspberry Pi receives a ping response from the Wi-Fi router then we have network connectivity. If the we don’t get any response then we’ll turn wlan0 off and back on.

Copy and paste following script and save it (check_wifi.sh) i have all my cron schedules scripts saved under /var/www/cron you can save it to anywhere you like.

#!/bin/bash
#=================================================================
# Script Variables Settings
clear
wlan='wlan0'
gateway='192.168.99.1'
alias ifup='/sbin/ifup'
alias ifdown='/sbin/ifdown'
alias ifconfig='/sbin/ifconfig'
#=================================================================
echo "  _____    _   _    _                            "
echo " |  __ \  (_) | |  | |                           "
echo " | |__) |  _  | |__| |   ___    _ __ ___     ___ "
echo " |  ___/  | | |  __  |  / _ \  | |_  \_ \   / _ \ "
echo " | |      | | | |  | | | (_) | | | | | | | |  __/"
echo " |_|      |_| |_|  |_|  \___/  |_| |_| |_|  \___|"
echo " "
echo "    S M A R T   H E A T I N G   C O N T R O L "
echo "*************************************************************************"
echo "* PiHome is Raspberry Pi based Central Heating Control systems. It runs *"
echo "* from web interface and it comes with ABSOLUTELY NO WARRANTY, to the   *"
echo "* extent permitted by applicable law. I take no responsibility for any  *"
echo "* loss or damage to you or your property.                               *"
echo "* DO NOT MAKE ANY CHANGES TO YOUR HEATING SYSTEM UNTIL UNLESS YOU KNOW  *"
echo "* WHAT YOU ARE DOING                                                    *"
echo "*************************************************************************"
echo
echo "                                                           Have Fun - PiHome" 
date
echo " - Auto Reconnect Wi-Fi Status for $wlan Script Started ";
echo

# Only send two pings, sending output to /dev/null as we don't want to fill logs on our sd card. 
# If you want to force ping from your wlan0 you can connect next line and uncomment second line 
ping -c2 ${gateway} > /dev/null # ping to gateway from Wi-Fi or from Ethernet
# ping -I ${wlan} -c2 ${gateway} > /dev/null # only ping through Wi-Fi 

# If the return code from ping ($?) is not 0 (meaning there was an error)
if [ $? != 0 ]
then
    # Restart the wireless interface
    ifdown --force wlan0
    ifup wlan0
	sleep 5
	ifup wlan0
fi
ping -I ${wlan} -c2 ${gateway} > /dev/null
date
echo 
echo " - Auto Reconnect Wi-Fi Status for $wlan Script Ended ";

#!/bin/bash

#=================================================================

# Script Variables Settings

clear

wlan='wlan0'

gateway='192.168.99.1'

alias ifup='/sbin/ifup'

alias ifdown='/sbin/ifdown'

alias ifconfig='/sbin/ifconfig'

#=================================================================

echo " _____ _ _ _ "

echo " | __ \ (_) | | | | "

echo " | |__) | _ | |__| | ___ _ __ ___ ___ "

echo " | ___/ | | | __ | / _ \ | |_ \_ \ / _ \ "

echo " | | | | | | | | | (_) | | | | | | | | __/"

echo " |_| |_| |_| |_| \___/ |_| |_| |_| \___|"

echo " "

echo " S M A R T H E A T I N G C O N T R O L "

echo "*************************************************************************"

echo "* PiHome is Raspberry Pi based Central Heating Control systems. It runs *"

echo "* from web interface and it comes with ABSOLUTELY NO WARRANTY, to the *"

echo "* extent permitted by applicable law. I take no responsibility for any *"

echo "* loss or damage to you or your property. *"

echo "* DO NOT MAKE ANY CHANGES TO YOUR HEATING SYSTEM UNTIL UNLESS YOU KNOW *"

echo "* WHAT YOU ARE DOING *"

echo "*************************************************************************"

echo

echo " Have Fun - PiHome"

date

echo " - Auto Reconnect Wi-Fi Status for $wlan Script Started ";

echo

# Only send two pings, sending output to /dev/null as we don't want to fill logs on our sd card.

# If you want to force ping from your wlan0 you can connect next line and uncomment second line

ping -c2 ${gateway} > /dev/null # ping to gateway from Wi-Fi or from Ethernet

# ping -I ${wlan} -c2 ${gateway} > /dev/null # only ping through Wi-Fi

# If the return code from ping ($?) is not 0 (meaning there was an error)

if [ $? != 0 ]

then

# Restart the wireless interface

ifdown --force wlan0

ifup wlan0

sleep 5

ifup wlan0

ping -I ${wlan} -c2 ${gateway} > /dev/null

date

echo

echo " - Auto Reconnect Wi-Fi Status for $wlan Script Ended ";

Make your script executable by running following command

chmod +x /var/www/cron/check_wifi.sh

1	chmod +x /var/www/cron/check_wifi.sh

Test Auto Reconnecting Wi-Fi Script

First run following command to test there are not errors in your script.

sh /var/www/cron/check_wifi.sh

1	sh /var/www/cron/check_wifi.sh

After successful execution of Auto Reconnecting Wi-Fi script you should get output as below.

Auto Reconnecting Wi-Fi on a Raspberry Pi

Lets add Auto Reconnecting Wi-Fi script to cron schedule so this script runs every five minutes. run crontab -e command and add following line to your crontab, make sure you add >/dev/null 2>&1 otherwise you will end up burning your SD card with unnecessary logs.

crontab -e

*/5 * * * * sh /var/www/cron/check_wifi.sh >/dev/null 2>&1

crontab -e

*/5 * * * * sh /var/www/cron/check_wifi.sh >/dev/null 2>&1

Lets do more testing taking down wlan0 and let script to restart Wi-Fi.

Note: running following command will immediately disconnect your shell session. and you have to wait for cron job to start your Wi-Fi it shouldn’t take more then 5 minutes.

ifdown --force wlan0

1	ifdown --force wlan0

After waiting for cron job to run auto reconnecting Wi-Fi script you can try to ssh to your raspberry pi. Assuming everything worked as it should your raspberry pi should reconnect to Wi-Fi. You can adjust time of script to what ever you value you like.

21 comments

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Sombody

October 27, 2017 at 3:50 pm

Short and effective, great work thanks 🙂
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alan

October 28, 2017 at 8:29 am

your wifi check (Auto Reconnect WiFi ) script with power management settings worked great
good work, keep it up
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Garey

February 16, 2018 at 12:02 pm

Hi this is great work, i couldn’t solve this puzzle myself, my rpi disconnect wifi connection at random interval to my home wifi but your script helped to keep raspberry pi connected to wifi specially this script to check wifi connection.
Now I m wondering if there is an easy way to detect configured wifi availability and if none of configured wifi available then RPI act as wifi access point so I can connect to it but as soon as wifi become available it connect to wifi but only fall back to wifi access point when no wifi is available. I have read lots of tutorials on how to setup rpi as access point may be you can help setup raspberry pi act as access point when no wifi is available.
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  Admin
  
  February 18, 2018 at 1:28 am
  
  Hi Garey, glade this post helped you, i had similar issue with raspberry pi wifi setup each time i want to change my wifi password i have to go back and change password in pi first then change password of my wifi router. i m working on on script to make pi as access point when no wifi is available but there are some dependencies i.e. not all wifi dongle are support to act as wifi access point but its work in progress and i’ll update here once i have something working….
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Athanasios

February 25, 2018 at 12:37 pm

When i run “ifdown –force wlan0” i get this “ifdown: unknown interface wlan0”
Does anyone know what is wrong?
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  Admin
  
  February 25, 2018 at 11:41 pm
  
  @Athanasios
  do you have wifi configured? your WiFi connected? it might be wlan1 interface try this and me know.
  Admin
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Asker

March 25, 2018 at 3:24 pm

Hello,
I’ve got a problem with your script or especially with cron executing the script. If I test the script manually everything works fine. But crontab can’t do the auto reconnect. I’ve made only two changes: The file has a different name and the location is different to yours (/usr/local/bin/network_status.sh)
Do you’ve got any idea why it isn’t working?
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  Admin
  
  March 25, 2018 at 4:20 pm
  
  @Asker,
  can you try to add following line to your crontab, and mke sure you are logged in as root so all cron jobs run as root. this line will create log and save it to /usr/local/bin/reboot_wifi.log once you have log file you can share here to get some suggestions.
  
  */5 * * * * sh /usr/local/bin/network_status.sh >> /usr/local/bin/reboot_wifi.log 2>&1
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Asker

March 25, 2018 at 5:51 pm

It’s a long log file but here are the first trials 🙂

‘unknown’: I need something more specific.
Sun 25 Mar 18:40:02 CEST 2018
– Auto Reconnect Wi-Fi Status for wlan0 Script Started

connect: Network is unreachable
ifdown: waiting for lock on /run/network/ifstate.wlan0
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ping: Warning: source address might be selected on device other than wlan0.
Sun 25 Mar 18:40:46 CEST 2018

– Auto Reconnect Wi-Fi Status for wlan0 Script Ended
‘unknown’: I need something more specific.
Sun 25 Mar 18:45:02 CEST 2018
– Auto Reconnect Wi-Fi Status for wlan0 Script Started

connect: Network is unreachable
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ping: Warning: source address might be selected on device other than wlan0.
Sun 25 Mar 18:45:51 CEST 2018

– Auto Reconnect Wi-Fi Status for wlan0 Script Ended
‘unknown’: I need something more specific.
Sun 25 Mar 18:50:02 CEST 2018
– Auto Reconnect Wi-Fi Status for wlan0 Script Started

connect: Network is unreachable
ifdown: waiting for lock on /run/network/ifstate.wlan0
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ifup: interface wlan0 already configured
ping: Warning: source address might be selected on device other than wlan0.
Sun 25 Mar 18:50:46 CEST 2018
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  Admin
  
  March 25, 2018 at 6:48 pm
  
  did you change gateway=’192.168.99.1′ variable to your router ip address?
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Asker

March 25, 2018 at 6:52 pm

Yes like I said bevor. If I run the test “sudo ifdown –force wlan0” everything is working fine..
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  Admin
  
  March 25, 2018 at 6:55 pm
  
  can you try to run your script while you are logged in
  
  sh /usr/local/bin/network_status.sh
  
  and what you see there ?
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Asker

March 25, 2018 at 6:58 pm

Also Yes!

Sun 25 Mar 20:57:29 CEST 2018
– Auto Reconnect Wi-Fi Status for wlan0 Script Started

Sun 25 Mar 20:57:31 CEST 2018

– Auto Reconnect Wi-Fi Status for wlan0 Script Ended
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  Admin
  
  March 25, 2018 at 7:27 pm
  
  can you try this code, this should ping your gateway,
  
  #!/bin/bash #================================================================= # Script Variables Settings clear wlan='wlan0' gateway='192.168.99.1' alias ifup='/sbin/ifup' alias ifdown='/sbin/ifdown' alias ifconfig='/sbin/ifconfig' #================================================================= date echo "Auto Reconnect Wi-Fi Status for $wlan Script Started "; echo ping -c2 ${gateway} if [ $? != 0 ] then ifdown --force wlan0 ifup wlan0 sleep 5 ifup wlan0 fi ping -I ${wlan} -c2 ${gateway} date echo echo "Auto Reconnect Wi-Fi Status for $wlan Script Ended ";
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Asker

March 25, 2018 at 8:04 pm

Sun 25 Mar 22:03:53 CEST 2018
Auto Reconnect Wi-Fi Status for wlan0 Script Started

PING 10.0.0.138 (10.0.0.138) 56(84) bytes of data.
64 bytes from 10.0.0.138: icmp_seq=1 ttl=64 time=8.08 ms
64 bytes from 10.0.0.138: icmp_seq=2 ttl=64 time=7.59 ms

— 10.0.0.138 ping statistics —
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 7.591/7.837/8.083/0.246 ms
PING 10.0.0.138 (10.0.0.138) from 10.0.0.12 wlan0: 56(84) bytes of data.
64 bytes from 10.0.0.138: icmp_seq=1 ttl=64 time=3.72 ms
64 bytes from 10.0.0.138: icmp_seq=2 ttl=64 time=6.04 ms

— 10.0.0.138 ping statistics —
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 3.720/4.882/6.044/1.162 ms
Sun 25 Mar 22:03:55 CEST 2018

Auto Reconnect Wi-Fi Status for wlan0 Script Ended
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  Admin
  
  March 25, 2018 at 8:46 pm
  
  @Asker
  now clear log file and let it run in cron and compare the output, i just trying to get picture why its not working.
  Admin
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Asker

March 26, 2018 at 1:46 pm

‘unknown’: I need something more specific.
Mon 26 Mar 15:00:01 CEST 2018
Auto Reconnect Wi-Fi Status for wlan0 Script Started

connect: Network is unreachable
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ping: Warning: source address might be selected on device other than wlan0.
PING 10.0.0.138 (10.0.0.138) from 0.0.0.0 wlan0: 56(84) bytes of data.

— 10.0.0.138 ping statistics —
2 packets transmitted, 0 received, 100% packet loss, time 1038ms

Mon 26 Mar 15:00:46 CEST 2018

Auto Reconnect Wi-Fi Status for wlan0 Script Ended
‘unknown’: I need something more specific.
Mon 26 Mar 15:05:01 CEST 2018
Auto Reconnect Wi-Fi Status for wlan0 Script Started

connect: Network is unreachable
ifdown: waiting for lock on /run/network/ifstate.wlan0
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ifup: waiting for lock on /run/network/ifstate.wlan0
ifup: interface wlan0 already configured
ping: Warning: source address might be selected on device other than wlan0.
PING 10.0.0.138 (10.0.0.138) from 0.0.0.0 wlan0: 56(84) bytes of data.

— 10.0.0.138 ping statistics —
2 packets transmitted, 0 received, 100% packet loss, time 1039ms

Mon 26 Mar 15:05:51 CEST 2018

Auto Reconnect Wi-Fi Status for wlan0 Script Ended
…
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Asker

March 29, 2018 at 8:59 pm

So you have also no idea where the problem lies?
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  Admin
  
  March 30, 2018 at 12:07 pm
  
  i tried to replicate your issue but so far can i m unsuccessful, can you try following script i have this running for very long time and never had issue, and can you create cron tab while logged in as root, ame make sure you have change the settings to allow root login as per OS (Raspbian Jessie) Installation and WiFi Configuration
  
  echo "*************************************************************************" date ################################################################## # Settings # Where and what you want to call the Lockfile lockfile='/var/www/cron/reboot_wifi.pid' # Which Interface do you want to check/fix wlan='wlan0' gateway='192.168.99.1' alias ifup='/sbin/ifup' alias ifdown='/sbin/ifdown' alias ifconfig='/sbin/ifconfig' ################################################################## echo echo "Starting WiFi check for $wlan" echo # Check to see if there is a lock file if [ -e $lockfile ]; then # A lockfile exists... Lets check to see if it is still valid pid=cat $lockfile
  # if kill -0 &>1 > /dev/null $pid; then
  if kill -0 &>1 $pid; then
  # Still Valid... lets let it be...
  echo "Process still running, Lockfile valid"
  exit 1
  else
  # Old Lockfile, Remove it
  echo "Old lockfile, Removing Lockfile"
  rm $lockfile
  fi
  fi
  # If we get here, set a lock file using our current PID#
  echo "Setting Lockfile"
  echo $$ > $lockfile
  
  # We can perform check
  echo "Performing Network check for $wlan"
  # Only send two pings, sending output to /dev/null
  
  #ping -c2 ${gateway} #> /dev/null
  ping -c2 ${gateway}
  # If the return code from ping ($?) is not 0 (meaning there was an error)
  if [ $? != 0 ]
  then
  # Restart the wireless interface
  ifdown --force wlan0
  sleep 5
  ifup wlan0
  fi
  #ping -I ${wlan} -c2 ${gateway} > /dev/null
  ping -I ${wlan} -c2 ${gateway}
  
  # Check is complete, Remove Lock file and exit
  #echo "process is complete, removing lockfile"
  rm $lockfile
  echo "Reboot WiFi Script Ended"
  date
  exit 0
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Matheus

October 18, 2018 at 2:57 pm

Thank you for sharing.
I did this to get the gateway address:
gateway=$(ip route get 8.8.8.8 | grep via | cut -d ‘ ‘ -f 3)
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  Admin
  
  October 18, 2018 at 3:17 pm
  
  @Matheus,
  doesnt work for me but running command in shell gives gateway ip
  ip route get 8.8.8.8 | grep via | cut -d ' ' -f 3

Auto Reconnecting Wi-Fi Script

Test Auto Reconnecting Wi-Fi Script

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