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Sunday, March 23, 2008

How to get email and sms notifications from your server

Ever wondered if you could make you server send you an email or a sms to your cell phone if it ever went down, or if you logs folder were too big, or any other event that you can think? Well, here's a really simple way of doing so.

In my case, I'll be using two events, one if the server goes down, and another if my logs folder gets too big (I have a very simple Linux box that does not have file rotation).

1- Mayday, server is down

There are two ways we can do this, and it will depend on how often do you need to check if the server is down. If you need it to be done every minute or so, I'd advise using a service instead of crontab. I could not personally say what's the system hog difference, but I'm open for feedbacks. In my case I'll be checking every hour, so I'll use crontab.

Other thing required is a cli email client, and there are many you can use. I choose msmtp, which is extremely easy to configure. Here's what I have set to use my gmail account:

tls on
tls_certcheck off
logfile ~/.msmtp.log
account gmail
port 587
auth on
password ######
account default : gmail

To send an email is as easy as:

$ echo -e "Subject: Test \n\n This is the message body" | msmtp -v email@address1 email@address2

So now that we have means to send the message, let's create the script. Remember that the script will need to be run from another PC and not from the server. A server that is down cannot send emails!!


## pings the server IP. Here I'm using only one ping as some distros ping 4x times (Fedora), and others will ping consecutively by default (Ubuntu)
ping -c 1 server

## checks if the ping was successful or not, if not it sends an email and a sms with the last time it tried to ping
if [ “$?” != “0” ] ; then
echo -e "Subject: Server is down \n\n Victor, \n Server is down. Last time tested was $(date)." | msmtp -v

Now we add the script to your crontab and send any error msg to a txt. Make sure that your account has pinging privileges

$ crontab -e
# Check if server is up every hour
0 * * * * /home/user/bin/ 2>> /home/user/var/log/server-up-log.txt

2- Checking /var/logs size

The process here will be almost the same, however both script and crontab need to be run on the server. Our script should look something like:


## Some txt editing. We will check /var/log size by using “df” and then striping it down to numbers only
e=`df -h | grep 'var\/log' | awk '{ print $5 ;}' | sed 's/%//'`

## If the size of /var/log gets higher than 75% we will get an email and a sms
if [ "$e" -gt "75" ] ; then
echo -e "Subject: Log folder \n\n Victor, \n Log folder has reached 75%" | msmtp -v

Add the script to your crontab on the server and you are done.

Have fun!!!


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