How to Create a Shell Script to Start MYSQL Server if is Crashing

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I have a couple of sites hosted on digitalocean VPS with Nginx and Virtualmin, but from time to time I find the mysql down and the annoying message that database can’t be reached. I have tried finding why the MYSQL is down but till now no luck no error message in the logs.

For my sites to not be down for hours I have created a shell script that is checking the mysql processes and in case are down it is starting the service again. I have added it in crontab and it is checking the service from 5 to 5 minutes with a log. I needed something simple that would start mysql in the case is down. Nothing fancy works well with CentOS 6 and 7.

Below are the steps to have the shell script running in crontab that is checking the mysql status and brings it up if down.

Step 1: Open terminal and login to the server

You can use putty or a similar ssh problem to access the server via SSH. Without SSH the script can’t be created.

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Step 2: Create the sh script

The script and the log would be placed in /home. Just do the below:

cd /home

nano sqlrestart.sh

 

Step 3: Create the shell instruction

I am checking for the programs to see if the mysql processes are up. In my case 2 processes are up, so the script in case not 2 processes are up would trigger the start:

To check the number:

[root@ns1 home]# pgrep mysql | wc -l
2

CentOS 7

#!/bin/bash
UP=$(pgrep mysql | wc -l);
if [ "$UP" -ne 2 ];
then
        echo "MySQL is down.";
        /sbin/service mysql start

else
        echo "All is well.";
fi

CentOS 6

#!/bin/bash
UP=$(pgrep mysql | wc -l);
if [ "$UP" -ne 2 ];
then
        echo "MySQL is down.";
        /sbin/service mysqld start

else
        echo "All is well.";
fi

Step 4: Save the file

Once you are done with the script press CTRL + x and you will be asked to save the changes. Type Y and hit enter. You will be returned to terminal and msqlrestart.sh file will be created in the root directory.

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Step 5: Give execution permissions

To be able to run the script would need to have the execution permission, to do this do:

chmod +x sqlrestart.sh

Step 6: Add it in crontab

Now you just need to do is to added in the crontab so it can be run from 5 to 5 min to check the status:

-open crontab

export EDITOR=nano
crontab -e

-add the script at the end:

*/5 * * * * /home/sqlrestart.sh >> /home/sqlrestart.log 2>&1

You can save it as in the step 4.

Now you just need to do is to test it. Just stop the

Just stop the mysql with:

CentOS 6: 

/sbin/service mysqld stop

CentOS 7 : 

/sbin/service mysql stop

After wait for couple of minutes and check the /home/sqlrestart.log

more/home/sqlrestart.log

This is what I have done on my server to prevent the downtime caused by mysql not beeing started or in case a crash happens. It works perfect for me. In case you want a different approach where the status is  checked and not the processes you can check:

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http://cssjockey.com/how-to-create-a-cron-job-to-start-mysql-if-it-stops/

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