How to make Raspberry shutdown when internet/lan disconnected

Question

I've already seen this link How to make Raspberry shutdown when I unplug the ethernet cable, but this solution does not work on Raspbian stretch since its network interface file/folder structure is changed.

My Raspberry pi is headless and battery powered (assume that it will give backup around 10min), so whenever electricity is gone for long time I want it to shutdown properly. Also note that when electricity goes down my network also goes down, so can't use ssh.

Any suggestion?

Answer 1

use post-up and post-down hook options in network script /etc/network/interfaces ,

you can create a simple script for shutdown, lets call it sd.sh executing which system will be shut down, so your network interfaces script will look like

# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp
    post-down ~myPath~/sd.sh

Answer 2

EDIT 2: You can use a dhcpcd exit hook script. The script is called on each dhcpcd event and checks the reason for calling dhcpcd and the related interface.

Create the script /etc/dhcpcd.exit-hook (usually it doesn't exists, otherwise edit it):

if [ "$reason" = NOCARRIER ] && [ "$interface" = eth0 ]
then
  echo "$(date) - eth0 DOWN, will shutdown now" >> /log/eth0_shutdown.log
  poweroff
fi

Note that this script file doesn't need to have a first line like #!/bin/bash and it also doesn't need to be set as executable.

Create the folder /log if it doesn't exists

sudo mkdir /log

---

Edit 1: If a cron job is too slow, then a while loop may be used instead. Adjust the sleep time as required.

#!/bin/bash

while [ $(cat /sys/class/net/eth0/operstate) == "up" ]
do
  sleep 10
done
echo "LAN is down, will shutdown now"
poweroff

---

First answer

You can monitor the interface status with a script which is regularly called by a cron job.

if [ $(cat /sys/class/net/eth0/operstate) == "down" ]
then 
   echo "LAN is down, will shutdown now"
   poweroff
fi

Answer 3

Got a better solution... I've used the lan connection for internet and configure the wifi as AP using the following link https://github.com/SurferTim/documentation/blob/6bc583965254fa292a470990c40b145f553f6b34/configuration/wireless/access-point.md

Then connect to the AP using mobile (android) with any ssh client and send the shutdown command to shut it down properly.