#centos 6 server

Monit is a very popular and lightweight Linux server monitoring tool used by the system administrators all over. Besides monitoring, it can be used to restart programs that are misbehaving, as well as check files and directories for changes, and monitor network connections to remote servers. Monit also allows user scripts, so you can monitor whatever you ask it to (nicely)! Today we'll demonstrate a simple, but practical, script to have Monit check a MySQL process running and restart it automatically if it’s stopped or not responding! Monit can usually be found in CentOS' official repository, so the easiest way to install Monit on your CentOS 6 server is to use yum package manager:

ServerSuit ~# yum install monit -y

Once Monit is installed, you’ll need to configure it. The configuration file is called monitrc and you can find it in /etc/monitrc directory, and we'll use it to create a monitoring config for our MySQL server, which checks if MySQL service is running every 2 minutes, and restart it if it's down. There are three types of commands Monit accepts:

1. Set statements – these are for basic Monit settings like used ports, checks interval and log files location.

set daemon 120                    # Check services ar 2-minute intervals set logfile /var/log/monit.log    # set log file path set mailserver mail.ServerSuit.com # set mailserver for alert delivery set httpd port 2812               # Run web server on port 2812  allow localhost                 # Allow localhost to connect  allow user:pass                 # require Username(user)and password(pass)

2. Include statements – it’s a good idea to keep the main files more compact and use separate config file for every service monitored, but for this exercise we have only one service, so let’s ignore these for now.

3. Service entry statements - here you can specify the programs you want to be managed by Monit.

check process mysqld with pidfile /var/run/mysqld/mysqld.pid start program = "/etc/init.d/mysql start" stop program = "/etc/init.d/mysql stop" if failed host 127.0.0.1 port 3306 then restart if 5 restarts within 5 cycles then timeout

Our Monit configuration is ready, but, of course, we gotta check the configuration file for possible syntax errors:

ServerSuit ~# monit -t

If there aren't any errors, you're good to go!

ServerSuit ~# monit start all

Done! Now if you shutdown MySQL server by using ‘service mysql stop’ command you'll see that in about 2 minutes, Monit will restart the service itself! You can check service status using the console with command ‘monit status’, or you can configure Monit web interface access in a config file. Currently, Monit is set up to allow access only from the server itself for security reasons, so you’ll need to change the config file, or use Nginx as reverse proxy server as described in our previous article.

This setup isn't really that complicated, but you can still save yourself a lot of time by using ServerSuit to set up Monit! You'll get our convenient software list when you sign up:

Then all you have to do is click that Monit button, and ServerSuit will push a preconfigured version of Monit to your server.

ServerSuit is free for 30-days when you first sign up, so there's literally never a bad time to try it out!

Nginx (pronounced as "engine x") is a very popular web server used by some of the most highly visited sites out there. Nginx is notable due to its stability and low resource footprint. So let's set one up!

There are 2 ways to install nginx. 1. Directly from source 2. Pre-build package.

Using the same CentOS 6 server, easiest way to install nginx is using package from repository. You always can download latest version of nginx from https://www.nginx.com/ and compile it from the source. Installing from repository pretty simple really, just put the following into command line.

# yum install nginx

Configuration Nginx configuration file is called nginx.conf and you can find it in /etc/nginx. The most basic configuration will look like the block below

events { } http { server { } }

This configuration will tell nginx to function as a http server, but before anything happens you need to start nginx:

# service nginx start

Since we're here, why don't we just keep Apache as our web server and work with clients directly as before. The problem with Apache is that it will consume a large amount of server resources (RAM especially) when it has to deal with increasing numbers of clients. Not only that, but a lot of this memory load is dependent on the clients' internet connections. That's because Apache will keep data in its available memory pool until all the data is sent to the client. So what does Nginx bring to the table? To help you understand, here's example where nginx is using as proxy server for LAMP stack.

user nobody nogroup; worker_processes 1; events {    worker_connections 512; } server {    listen *:80;    root /var/www/iLoveLinuxSuit;    index index.php index.htm index.html;    server_name LoveLinuxSuit.com;    location / {        try_files $uri $uri/ /index.php;    }    location ~ \.php$ {        proxy_pass http://127.0.0.1:8080;    } }

In this configuration, the proxy server will receive every incoming request to port 80 and forward them to Apache server 127.0.0.1 port 8080 (we actually need to manually change its listen port to 8080 at /etc/httpd/httpd.conf and restart Apache).

Then every client request will be processed by Apache and passed to nginx; server resources immediately became free for another client, while nginx can send back request results to the client.

Let’s reload nginx and we are ready:

# service nginx restart

Overall, it's not too difficult. So how can ServerSuit help? Oh hey, check out our software library.