Simple bash script to monitor your webserver remotely on different ports

Posted Thu, 02/12/2009 - 18:10 by ma

Simple bash script to monitor a webserver on different ports (here smtp, dns, http & https but it can be customized) I'm sure there is over 100 available programs doing this but I wanted something with small memory usage. Also, I only wanted to be notified once, notifications are receive by SMS on my cell. With the software I was using before, I was getting notified every minute until I could reach a computer and fix the problem or stop monitoring which was quite annoying.

A BETTER VERSION OF THE SCRIPT USING NMAP INSTEAD OF TELNET IS AVAILABLE HERE

Software installation

You need mail, dig and telnet installed.

The script

NOTE : The script will not continue until you do :

./whatever_you_called_this_script fix

This is done on purpose to receive only ONE notification...

#!/bin/bash
# Script to check important ports on remote webserver
# Copyright (c) 2009 blogama.org
# This script is licensed under GNU GPL version 2.0 or above
# ---------------------------------------------------------------------
 
### This script does a verification on port 25, 53, 80 and 443 ###
### After 2 failed check it will send a mail notification ###
 
######To be modified######
 
WORKDIR="/root"
 
###HTTP###
HTTPSERVERIP="192.168.1.106"
HTTPSERVERPORT="80"
##########
 
###HTTPS###
HTTPSSERVERIP="192.168.1.106"
HTTPSSERVERPORT="443"
##########
 
###MAIL###
SMTPSERVERIP="192.168.1.106"
SMTPSERVERPORT="25"
##########
 
###DNS###
DNSSERVERIP="192.168.1.106"
DOMAINTOCHECKDNS="example.com"
ANSWERIP="192.168.1.106"
#########
 
###NOTIFICATIONS###
EMAIL="admin@example.com"
##########
 
######End to be modified######
 
 
######Do not make modifications below######
### Binaries ###
MAIL=$(which mail)
TELNET=$(which telnet)
DIG=$(which dig)
 
###Change dir###
cd $WORKDIR
 
###Restore when problem fix###
if [ $1 ]; then
  if [ $1=="fix" ]; then
    rm server_problem*.txt
	exit 1;
  fi
fi
 
###Check if already notified###
if [ -f server_problem.txt ]; then
  exit 1;
fi
 
###Test SMTP###
(
echo "quit"
) | $TELNET $SMTPSERVERIP $SMTPSERVERPORT | grep Connected > /dev/null 2>&1
 
if [ "$?" -ne "1" ]; then #Ok
  echo "PORT CONNECTED"
  if [ -f server_problem_first_time_smtp.txt ]; then #remove file if problem fixed
    rm -rf server_problem_first_time_smtp.txt
  fi
else #Connection failure
  if [ -f server_problem_first_time_smtp.txt ]; then #Second time, send notification below
    echo "SMTP PORT NOT CONNECTING" >> server_problem.txt
	rm -rf server_problem_first_time_smtp.txt
  else #First notification
    > server_problem_first_time_smtp.txt
  fi
fi
 
###Test HTTP###
(
echo "quit"
) | $TELNET $HTTPSERVERIP $HTTPSERVERPORT | grep Connected > /dev/null 2>&1
 
if [ "$?" -ne "1" ]; then #Ok
  echo "PORT CONNECTED"
  if [ -f server_problem_first_time_http.txt ]; then #remove file if problem fixed
    rm -rf server_problem_first_time_http.txt
  fi
else #Connection failure
  if [ -f server_problem_first_time_http.txt ]; then #Second time, send notification below
    echo "HTTP PORT NOT CONNECTING" >> server_problem.txt
	rm -rf server_problem_first_time_http.txt
  else #First notification
    > server_problem_first_time_http.txt
  fi
fi
 
###Test HTTPS###
(
echo "quit"
) | $TELNET $HTTPSSERVERIP $HTTPSSERVERPORT | grep Connected > /dev/null 2>&1
 
if [ "$?" -ne "1" ]; then #Ok
  echo "PORT CONNECTED"
  if [ -f server_problem_first_time_https.txt ]; then #remove file if problem fixed
    rm -rf server_problem_first_time_https.txt
  fi
else #Connection failure
  if [ -f server_problem_first_time_https.txt ]; then #Second time, send notification below
    echo "HTTPS PORT NOT CONNECTING" >> server_problem.txt
	rm -rf server_problem_first_time_https.txt
  else #First notification
    > server_problem_first_time_https.txt
  fi
fi
 
 
 
###Test DNS###
$DIG $DOMAINTOCHECKDNS @$DNSSERVERIP | grep $ANSWERIP
 
if [ "$?" -ne "1" ]; then #Ok
  echo "PORT CONNECTED"
  if [ -f server_problem_first_time_dns.txt ]; then #remove file if problem fixed
    rm -rf server_problem_first_time_dns.txt
  fi
else #Connection failure
  if [ -f server_problem_first_time_dns.txt ]; then #Second time, send notification below
    echo "DNS PORT NOT CONNECTING" >> server_problem.txt
	rm -rf server_problem_first_time_dns.txt
  else #First notification
    > server_problem_first_time_dns.txt
  fi
fi
 
###Send mail notification after 2 failed check###
if [ -f server_problem.txt ]; then
  $MAIL -s "Server problem" $EMAIL < /root/server_problem.txt
fi

make it executable : 

chmod +x whatever_you_called_this_script

Add the script to your crontab : 

* * * * * /root/check >/dev/null 2>&1

Comments

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hint: subroutine to bypass firewall

by bubez - 03/03/2009 - 05:18

Nice script, but if you have a firewall between you and the web server to check, the telnet command may hang; imagine a minimal situation where even nmap or wget commands are unavailable, but telnet is available. pls. pay attention of the format.
This is my suggestion:

#!/bin/bash
#copyleft michele dot mase at gmail dot com
HOST=www.google.it
PORT=80
OK=KO
TIMEOUT=1
#which is the pid of telnet
telnetpid () {
ps -ef|grep [t]elnet\ $HOST|awk '{print $2}'
}
#check if there is a hanged telnet session
sleep $TIMEOUT && [ -n "$(telnetpid)" ] && kill
$(telnetpid) && exit 1 &
#check telnet result
if telnet $HOST $PORT < /dev/null 2>&1 | grep -q Connected
then
OK=OK
else
OK=$OK
fi
echo Connection $HOST:$PORT=$OK
exit 0

Script results

by ebarber - 02/19/2009 - 12:51

Hi, This is the output when I run the script. Is this the output I want to see? Do I use the actual static IP of the server or use an internal localhost IP?

root@mojave:~# ./srvwatch.sh
Connection closed by foreign host.
PORT CONNECTED
Connection closed by foreign host.
PORT CONNECTED
Connection closed by foreign host.
PORT CONNECTED
; <<>> DiG 9.4.2-P2 <<>> mydomain.tld @11.111.111.111
PORT CONNECTED

output

by ma - 02/19/2009 - 14:21

Hi, you can remove all echo "PORT CONNECTED" if you dont want any output.

Do I use the actual static IP of the server or use an internal localhost IP?

I did this to monitor from a remote location. For example :

###DNS###
DNSSERVERIP="64.15.75.221"
DOMAINTOCHECKDNS="alivetesting.com"
ANSWERIP="64.15.75.200"
#########

would do 

dig alivetesting.com @64.15.75.221

good

by thazer - 02/13/2009 - 04:46

it's indeed usefull and yes very "lightwight" i'm running it from two boxes so i can monitor the services from a inet persepctive :) thanks!

pgn.ro