Network Config Recovery Script in Case of Failure

After encountering several times that the network on a remote host completely dropped during network configuration, making it difficult to restore access, this script was devised. During the debugging period, I set it to run in cron every 5 minutes, and then the script pings Google; if it fails, it applies known working settings.

#!/bin/bash

# Script for restoring network settings in case the server loses internet due to incorrect network configuration
# Requires ifupdown2, install via apt-get install ifupdown2


host=${1:-'8.8.8.8'}                                        # Host to be pinged, defaults to Google or first argument
source='/etc/network/interfaces_work'                       # Known working network config
destination='/etc/network/interfaces'                       # System network config
fail_conf='/etc/network/interfaces_fail'                    # Here failed configs will be stored
DATE=`date +"%H:%M %d/%m/%Y"`                               # Date and time
log=/home/network_restore.log                               # Log file


result=$(ping -c 1 $host | grep % | cut -d ' ' -f6)         # Ping and save result
if [[ "$result" = '0%' ]];then                              # If everything is ok
    echo $DATE ok   >> $log                                 # Log it
else                                                        # If no ping
    echo $DATE fail >> $log                                 # Log it
    echo $DATE >> $fail_conf                                # Log it

    echo >> $fail_conf                                      # Just for convenience
    echo >> $fail_conf
    echo >> $fail_conf
    echo '###################################################' >> $fail_conf

    cat $destination >> $fail_conf                          # Save the failed config
    cat $source > $destination                              # Overwrite

    ifdown -a                                               # Bring down the network
    ifup -a                                                 # Bring up the network with new settings

#   sleep 30
#   result=$(ping -c 1 $host | grep % | cut -d ' ' -f6)     # Ping and save result
#
#   if [[ "$result" = '0%' ]];then                          # If everything is ok
#       echo ok                                             #
#   else                                                    #
#       reboot                                              # If it didn't help, try rebooting the system
#   fi
fi