My Daily Works Archive

I will give an example of a simple script for restarting services if they are not running and sending a notification by email:

#!/bin/bash
SERVICES="ssh apache2 zabbix-server zabbix-agent mysql smbd nmbd asterisk"
DATE=$(date '+%d-%m-%Y %H:%M:%S')
 
for SERVICE in ${SERVICES}
 do
   service $SERVICE status 2>&1>/dev/null
    if [ $? -ne 0 ];
      then
        service $SERVICE stop
        sleep 3
        service $SERVICE start
        echo -e "Starting $SERVICE"
        (echo "Subject:Restarting $SERVICE"; echo "$DATE $SERVICE is not running on $HOSTNAME! Restarting!";) | sendmail test@ixnfo.com
      else
        echo -e "$SERVICE OK"
    fi
done

In the script, specify the email on which you want to receive notifications, and in the “SERVICES” list of services through the space that you want to check.
I first stopped the service in order to surely stop all possible processes, paused for 3 seconds and then started, because with the restart command, some highly loaded services could not start correctly and hang with the status “active (exited)”.

To make the script automatically run for example every 10 minutes, add a line to /etc/crontab:

1	`/10 * * * root /dir/watchdog.sh > /dev/null 2>&1`

Linux

Restarting a Linux Server via Web Browser (PHP)

20:59:00 ITExam_Blog No comments

After opening and reading every result on Google, I figured it's time to make my own thread somewhere.

I'm trying to setup a means of rebooting/doing other system functions through a web interface powered by HTML (for the buttons/text) and PHP (for the execution of the aforementioned functions).

I'm unable to get this to work. I've read that I need to add the web user to the sudoers file, and I've tried. I'm running Nginx on my server, how do I add the user to the sudoers in my case?

Also, I'm aware of the security risks, and would prefer not to be advised of them, thanks.

The following is what I have so far:

HTML:

HTML

<body>

<h3>Restart</h3>
<p>
<form action="restart.php" method="get">
  <input type="submit" value="Press me.">
</form>
</p>

</body>

PHP:

PHP

<?php
echo "This is a test";
echo "<br>";
echo "<br>";
echo shell_exec('ifconfig');
echo "<br>";
echo "<br>";
echo "Restarting server...";
exec ('/usr/bin/sudo /etc/init.d/portmap restart');
shell_exec("/sbin/reboot");
exec("/sbin/reboot");
system("/sbin/reboot");
?>

Mind you that here, I only have so many things attempting to execute, so that I make sure I hit the target when one of them works, if that makes sense. The IFConfig is just a test to make sure that it's actually able to execute.

Sudoers:

Text

# User privilege specification
root    ALL=(ALL:ALL) ALL
www-data reboot = NOPASSWD: /sbin/reboot

Hope help comes. Thanks.

---------------------------------------------

EDIT - I got a response from another location that fixed my problem. In the case that someone is dealing with a similar problem, here's the solution that helped me.

Text

You can do this either by editing your sudoers file :

Sudoers:
www-data ALL=(root) NOPASSWD: /sbin/reboot 

The first ALL is for the hostname if you're hostname is not 'reboot' I advise you to keep ALL as it will work in any hostname. That's why I don't seem to work on your server


restart.php:
exec('sudo /sbin/reboot');

Linux, MySQL

Use a script to restart critical Linux services such as the web or database server. Restart nginx, apache2, MySQL or PHP-fpm automatically.

21:09:00 ITExam_Blog No comments

If you manage your own WordPress web server then you have undoubtedly come across many situations where your web apache, nginx, MySQL or PHP-fpm services have stopped.

Sometimes the reason is unknown and things just crash from time to time.

Using the Linux crontab service we can write a simple bash script to test to see if these services have stopped and restart them.

You can use whatever editor you are comfortable with.

Here’s the command line code to create the file in nano:

sudo nano /opt/launch-crashed-services.sh

Here is the bash script.

#!/bin/bash

service mysql status | grep 'active (running)' > /dev/null 2>&1

if [ $? != 0 ]
then
        sudo service mysql restart > /dev/null
fi

service nginx status | grep 'active (running)' > /dev/null 2>&1

if [ $? != 0 ]
then
        sudo service nginx restart > /dev/null
fi

service php7.2-fpm status | grep 'active (running)' > /dev/null 2>&1

if [ $? != 0 ]
then
        sudo service php7.2-fpm restart > /dev/null
fi

Change the service names to the ones you are running, e.g. “apache2” or whatever PHP version you are running.

The script uses the service <name> status command to output the status of a particular service such as mysql.

We then run this through grep looking for the phrase “active (running)”.

If this is not found, we ask the system to restart the service.

Save the file to /opt/launch-crashed-services.sh

Then ensure that it is runnable from the command line using:

sudo chmod +x /opt/launch-crashed-services.sh

Scheduling Service Restarts Using Crontab

It would be a pain to have to SSH into our server every time a service crashes to run the script.

Instead we can call the script directly from a crontab service and have it running as frequently as we need it to.

Edit your root crontab list using:

sudo crontab -e

It’s important to use the root crontab using the command above and not to edit your own user profile crontab, otherwise, it will not work properly.

Add the following line to the bottom of the root crontab list:

*/1 * * * * /opt/launch-crashed-services.sh > /dev/null 2>

This will run the script every minute but you can change that for whatever works for your server.

Now if a critical service crashes, the server will attempt to restart it.

Happy days.

Centos, Linux, MySQL

How to Install MySQL 5.6 Server on CentOS / Redhat 6/7/8

17:46:00 ITExam_Blog No comments

Hello Friends, In this article I am going to explain how we can install MySQL 5.6 server in CentOS and Redhat 6/7/8 using yum command.

System requirements :

Server : CentOS release 6.7 (Final)
Architecture : i686 i386 GNU/Linux

Follow the below steps to install MySQL 5.6 server using yum command.

Install MySQL 5.6 server on CentOS and Redhat

# ssh root@serve_ip_and _hostname
# mkdir /root/dowload/
# cd /root/download/

Install wget

first of all install wget command on your machine if it is not installed by default. follow this below command to install wget.

# yum install wget

You will get back some output like below if you have already installed wget package.

Loaded plugins: fastestmirror
Setting up Install Process
\Loading mirror speeds from cached hostfile
* base: mirror.nbrc.ac.in
* epel: ftp.riken.jp
* extras: mirror.nbrc.ac.in
* updates: mirror.nbrc.ac.in
Package wget-1.12-8.el6.i686 already installed and latest version
Nothing to do

Download and Install mysql-community repo

Now download and install mysql-community repo

# wget http://repo.mysql.com/mysql-community-release-el6-5.noarch.rpm

--2016-11-25 06:30:03-- http://repo.mysql.com/mysql-community-release-el6-5.noarch.rpm
Resolving repo.mysql.com... 104.108.196.141
Connecting to repo.mysql.com|104.108.196.141|:80... connected.

Install mysql 5.6 server using yum command

Let’s install MysQL 5.6 server following below command:

#yum install mysql-server

Loaded plugins: fastestmirror
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: mirror.nbrc.ac.in
* epel: epel.mirror.net.in
* extras: mirror.nbrc.ac.in
* remi: mirrors.thzhost.com
* remi-php56: mirrors.thzhost.com
* remi-safe: mirrors.thzhost.com
* updates: mirror.nbrc.ac.in
ajenti | 2.5 kB 00:00
vz-base | 951 B 00:00
vz-updates | 951 B 00:00
Package mysql-server is obsoleted by mysql-community-server, trying to install mysql-community-server-5.6.34-2.el6.i686 instead
Resolving Dependencies
--> Running transaction check
---> Package mysql-community-server.i686 0:5.6.34-2.el6 will be installed
................................
....................
Install 5 Package(s)
Total size: 73 M
Installed size: 299 M
Is this ok [y/N]: y
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
Installing : mysql-community-common-5.6.34-2.el6.i686 1/5
Installing : mysql-community-libs-5.6.34-2.el6.i686 2/5
Installing : mysql-community-client-5.6.34-2.el6.i686 3/5
Installing : numactl-2.0.9-2.el6.i686 4/5
Installing : mysql-community-server-5.6.34-2.el6.i686 5/5
Verifying : mysql-community-common-5.6.34-2.el6.i686 1/5
Verifying : mysql-community-client-5.6.34-2.el6.i686 2/5
Verifying : numactl-2.0.9-2.el6.i686 3/5
Verifying : mysql-community-libs-5.6.34-2.el6.i686 4/5
Verifying : mysql-community-server-5.6.34-2.el6.i686 5/5
Installed:
mysql-community-server.i686 0:5.6.34-2.el6
Dependency Installed:
mysql-community-client.i686 0:5.6.34-2.el6 mysql-community-common.i686 0:5.6.34-2.el6 mysql-community-libs.i686 0:5.6.34-2.el6
numactl.i686 0:2.0.9-2.el6
Complete!

After installation completed restart mysql service using below command.

#service mysqld start

#/etc/init.d/ mysqld start

Note : We have installed MySQL server with blank root password. We will need to reset root password using “mysql_secure_installation” follow below instructions to reset password.

mysql_secure_installation

Follow this below command to install mysql secure installation.

# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
SERVERS IN PRODUCTION USE! PLEASE READ EACH STEP CAREFULLY!
In order to log into MySQL to secure it, we'll need the current
password for the root user. If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.
Enter current password for root (enter for none): <ENTER>
OK, successfully used password, moving on...
Setting the root password ensures that nobody can log into the MySQL
root user without the proper authorisation.
Set root password? [Y/n] <Type here “Y”>
New password:*****
Re-enter new password:*****
Password updated successfully!
Reloading privilege tables..
... Success!
By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them. This is intended only for testing, and to make the installation
go a bit smoother. You should remove them before moving into a
production environment.
Remove anonymous users? [Y/n] <Type here “Y”>
... Success!
Normally, root should only be allowed to connect from 'localhost'. This
ensures that someone cannot guess at the root password from the network.
Disallow root login remotely? [Y/n] < Type “ Y “ if you want to disable root remote loging for security purpose>
... Success!
By default, MySQL comes with a database named 'test' that anyone can
access. This is also intended only for testing, and should be removed
before moving into a production environment.
Remove test database and access to it? [Y/n] < Type “Y” >
... Success!
Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.
Reload privilege tables now? [Y/n]
... skipping.
All done! If you've completed all of the above steps, your MySQL
installation should now be secure.
Thanks for using MySQL!
Cleaning up...

Now login with you root password

#mysql -uroot -p

Enter password:*****

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 14

Server version: 5.6.34 MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

I hope this article will be helpful you to install MySQL 5.6 server on Centos and Redhat. If you have any queries and problem please comment in comment section.

My Daily Works Archive

Simple Watchdog script

Restarting a Linux Server via Web Browser (PHP)

Use a script to restart critical Linux services such as the web or database server. Restart nginx, apache2, MySQL or PHP-fpm automatically.

Scheduling Service Restarts Using Crontab

How to Install MySQL 5.6 Server on CentOS / Redhat 6/7/8

Install MySQL 5.6 server on CentOS and Redhat

Install wget

Download and Install mysql-community repo

Install mysql 5.6 server using yum command

mysql_secure_installation

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