Category: Scripting

Restart service automatically and get notified.

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So you are running you own webserver which at the times is short of resources and the services like MySQL and HTTPD stops – results your website is down until you get a chance to fix it.

Quick solution would be to implement a script which restarts services at such situations and emails you that the service was restarted – so you can later go and check what was the problem

So below is the script, which will make sure that HTTP , MySQL and Postfix is running all the time – It will check status of the service and if it’s stopped or Dead it will restart it.

How to Implement this Script ?

Setup a cron to run the script every minute – like below.

* * * * * root /home/bob/scripts/servicecheck.sh

Create a file called servicecheck.sh and put the code below.
Just change the email address in the script to yours and you are done.

#!/bin/bash

#####################
#MySQL CHECK
#####################

/sbin/service mariadb status > /var/log/mysqlservicestatus 2>&1
STATUS=$(cat /var/log/mysqlservicestatus | egrep 'dead|failed')

        if [[ $STATUS = "" ]]
        then
/bin/logger -t MYSQL IS RUNNING
else
/sbin/service mariadb restart
/bin/logger -t restarted mysql
echo "Restarted MYSQL" | /bin/mail -s "Restarted MYSQL" you@email.com
fi
echo > /var/log/mysqlservicestatus

#####################
#HTTPD CHECK
#####################

/sbin/service httpd status > /var/log/httpdservicestatus 2>&1
STATUS=$(cat /var/log/httpdservicestatus | egrep 'dead|failed')

        if [[ $STATUS = "" ]]
        then
/bin/logger -t httpd IS RUNNING
else
/sbin/service httpd restart
/bin/logger -t restarted httpd
echo "Restarted HTTPD" | /bin/mail -s "Restarted HTTPD" you@email.com
fi

echo > /var/log/httpdservicestatus


#####################
#POSTFIX CHECK
#####################

/sbin/service postfix status > /var/log/postfixservicestatus 2>&1
STATUS=$(cat /var/log/postfixservicestatus | egrep 'dead|failed')

        if [[ $STATUS = "" ]]
        then
/bin/logger -t postfix IS RUNNING
else
/sbin/service postfix restart
/bin/logger -t restarted postfix
echo "Restarted postfix" | /bin/mail -s "Restarted postfix" you@email.com
fi

You want to monitor other services, just go ahead and add it.

How to use Array in Bash Scripting

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First we will see what is Array in Linux

If you have been doing shell scripting, you must have definitely came across the term called variable. So when you use a variable, you can add a single name to the variable – In other words one variable can hold only one value.

Example of an Variable

#!/bin/bash
cityname="Berlin"
echo "$cityname"

So if you want to hold names of multiple cities, then you will have to create new variable for each city.

For an Example

cityname01="Berlin"
cityname02="Tokyo"
cityname03="Moscow"
cityname04="Rio"
cityname05="Denver"

However, to ease life we could use a single Array which could hold up all values in a single variable.

To define Array :-

cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"

So here we have stored all city Names in a Array called “cityname”. So now question is how do you access an Array.

You just need to echo it’s number 🙂 Like shown below.

#!/bin/bash
cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"
echo "${cityname[3]}"

So above script will print “Rio” If you want to print all city names then you would use

echo "${cityname[@]}"

OR

echo "${cityname[*]}"

You can copy paste the script below and run it which will help you understand better.

#!/bin/bash
cityname[0]="Berlin"
cityname[1]="Tokyo"
cityname[2]="Moscow"
cityname[3]="Rio"
cityname[4]="Denver"

echo Cities I love are : "${cityname[@]}"

Output would be.

Cities I love are : Berlin Tokyo Moscow Rio Denver