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The ping-detect script is designed to run specified commands when a monitored host stops responding to ping requests.
The first parameter taken by the ping-detect script is the hostname/IP address of the device to ping. Any other parameters are then regarded as a
command to run whenever the ping to the host fails. ping-detect can run any number of commands.
Below is an example using ping-detect to power cycle an RPC (PDU) outlet whenever a specific host fails to respond to a ping request. The ping-
detect runs from /etc/config/rc.local to make sure that the monitoring starts whenever the system boots.
Suppose we have a serially controlled RPC connected to port01 on a console server and have a router powered by outlet 3 on the RPC (and the
router has an internal IP address of 192.168.22.2). The following instructions will show you how to continuously ping the router. When the router
fails to respond to a series of pings, the console server will send a command to RPC outlet 3 to power cycle the router, and write the current
date/time to a file:
Copy the ping-detect script to /etc/config/scripts/ on the console server
Open /etc/config/rc.local using vi
Add the following line to rc.local:
/etc/config/scripts/ping-detect 192.168.22.2 /bin/bash -c "pmpower -l port01 -o 3 cycle && date" > /tmp/output.log &
The above command will cause the ping-detect script to continuously ping the host at 192.168.22.2 which is the router. If the router crashes, it will
no longer respond to ping requests. If this happens, the two commands pmpower and date will run. The output from these commands is sent to
the file /tmp/output.log so that we have a record. The ping-detect is also run in the background using the "&".
Remember the rc.local script only runs by default when the system boots. You can manually run the rc.local script or the ping-detect script if
desired.
The ping-detect script
The above is just one example of using the ping-detect script. The idea of the script is to run any number of commands when a specific host stops
responding to ping requests. Here are details of the ping-detect script itself:
#!/bin/sh
# Usage: ping-detect HOST [COMMANDS...]
# This script takes 2 types of arguments: hostname/IPaddress to ping, and the commands to
# run if the ping fails 5 times in a row. This script can only take one host/IPaddress per
# instance. Multiple independent commands can be sent to the script. The commands will be
# run one after the other.
#
# PINGREP is the entire reply from the ping command
# LOSS is the percentage loss from the ping command
# $1 must be the hostname/IPaddress of device to ping
# $2... must be the commands to run when the pings fail.
COUNTER=0
TARGET="$1"
shift
# loop indefinitely:
while true
do
# ping the device 10 times
PINGREP=`ping -c 10 -i 1 "$TARGET" `
#get the packet loss percentage
LOSS=`echo "$PINGREP" | grep "%" | sed -e 's/.* \([0-9]*\)% .*/\1/'`
if [ "$LOSS" -eq "100" ]
then
COUNTER=`expr $COUNTER + 1`
else
COUNTER=0