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rishimaharaj
Asked: 2012-05-26 05:40:35 +0800 CST

How to get updated IP address mailed to me in DNSExit?

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I'm using DNSExit on my Ubuntu server (Natty 11.04) and have installed the ipUpdate rpm file and did an apt-get install for chkconfig to enable the ipUpdate.

I'd like to get an email whenever the IP address changes, so that I can SSH into the box using PuTTY (because I can't unless I know the current IP address).

The current IP address is stored in /tmp/dnsexit-ip.txt, and I'd like to, whenever that file changes, to mail the contents of that file and the contents of /var/log/dnsexit.log (which contains a history of the IP changes) to my email address.

How can I accomplish this task? I'm thinking that a cronjob will be the solution, but I'm not sure how to do this.

cron

2 Answers

  1. Best Answer

    Prerequisites

    Install sendEmail. It's a lightweight, command line SMTP email client. We'll use it to send emails from a script, using a Gmail account.

    sudo apt-get install sendemail libio-socket-ssl-perl libnet-ssleay-perl

    Create the script

    Create a file named "ip-notify.sh" somewhere, for example in a "Scripts" directory in your home folder; make it executable, and open it up for editing.

    mkdir -p ~/Scripts && touch ~/Scripts/ip-notify.sh && chmod a+x ~/Scripts/ip-notify.sh && gedit ~/Scripts/ip-notify.sh

    Insert the following text in the file:

    #!/bin/bash

# Modify the following values!

  SENDERNAME="Computer" # This is the name that will show in the 'From' field. Purely esthetic.
  RECIPIENTNAME="Your Name" # This is the name that will show in the 'To' field. Also purely esthetic.
  GMAILADDRESS="[email protected]" # This is your Gmail address.
  GMAILUSER="someemail" # This is your Gmail username, without the '@gmail.com' part.
  GMAILPASS="password" # This is your Gmail password.

# You can stop modifying here

DIR=/tmp/
CURIP=dnsexit-ip.txt
IPLOG=/var/log/dnsexit.log
SMTPSERVER="smtp.gmail.com:587"

if [[ $(find $DIR -mmin -2 -name $CURIP) ]];
then
        echo "$CURIP has been modified in the last two minutes."
        # Send an email
        sendemail -u "IP Address" -m "IP address has changed!" -f "$SENDERNAME <$GMAILADDRESS>" -t "$RECIPIENTNAME <$GMAILADDRESS>" -s $SMTPSERVER -xu $GMAILUSER -xp $GMAILPASS -a $DIR$CURIP $IPLOG
fi

    Once that's done, save and close the file.

    Run the script periodically

    We'll run this script every two minutes. Open up your crontab.

    crontab -e

    Add the following line to the bottom of the file:

    */2 * * * * bash ~/Scripts/ip-notify.sh

    You're done!

    If all goes well, you should now get email updates when the IP address of your machine changes.

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  2. If you have a mail installed (I use postfix ... i.e. sudo apt-get install postfix) you can run a bash script in cron every 5 minutes.

    The script uses 'stat' to check if the file changed in the last five minutes (300 seconds) if so the $diff variable will equal 1.

    Some thing like this should work:

    #!/bin/bash
filemtime=`stat -c %Y /tmp/dnsexit-ip.txt`
currtime=`date +%s`
diff=$(( (currtime - filemtime) / 300 ))
x=1

if [ $diff -eq  $x ]
  then
    SUBJECT="DCHP CHANGE"
    EMAIL="[email protected]"
    EMAILMESSAGE="/tmp/emailmessage.txt"

    echo "Contents of dnsexit-ip.txt" >$EMAILMESSAGE
    cat /tmp/dnsexit-ip.txt >> $EMAILMESSAGE
    echo "Contents of dnsexit.log" >>$EMAILMESSAGE
    cat /var/log/dnsexit.log >> $EMAILMESSAGE

    sudo /usr/bin/mail -s "$SUBJECT" "$EMAIL" < $EMAILMESSAGE
 fi
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