Install Monit in CentOS Linux for Monitoring

Monit is an open source utility for managing and monitoring, processes, files, directories and filesystems on a UNIX system. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations. However, you are the master and monit would only do what you define in the config file for it to do. We will discuss here how to install and configure a basic monit installation in Centos or Redhat Linux.


Monit can start a process if it does not run, restart a process if it does not respond and stop a process if it uses too much resources. You can use Monit to monitor files, directories and filesystems for changes, such as timestamp changes, checksum changes or size changes. You can also monitor remote hosts; Monit can ping a remote host and can check TCP/IP port connections and server protocols. Monit is controlled via an easy to use control file based on a free-format, token-oriented syntax. Monit logs to syslog or to its own log file and notifies you about error conditions and recovery status via customizable alert. For more infop on monit you can visit their official site http://mmonit.com/monit/

Install Monit

The first, you need to enable EPEL (Extra Packages for Enterprise Linux) to install monit package. Login as root and type the following command:

[root@superman ~]# vi /etc/yum.repos.d/epel.repo

Add or uncomment the following content at end of the file

[epel] 

name=Extra Packages for Enterprise Linux 5 - $basearch 

mirrorlist=http://mirrors.fedoraproject.org/mirrorlist?

repo=epel-5&arch=$basearch

failovermethod=priority 

enabled=1 

gpgcheck=0

Save and close the file. And type the following command

[root@superman ~]# yum clean all

To install monit, type the following command

[root@superman ~]# yum install monit

Turn on monit when system start up

[root@superman ~]# chkconfig --levels 235 monit on

Configure Monit

The configuration file of monit in Centos or RedHat is /etc/monit.conf. Type the following command to edit

[root@superman ~]# vi /etc/monit.conf

Sampe configuration file

set daemon 60 

set logfile /var/log/monit.log 

set mailserver localhost 

set mail-format { from: alert@domain.com 

subject: $SERVICE $EVENT at $DATE 

message: Monit $ACTION $SERVICE at $DATE on $HOST: $DESCRIPTION.  } 

set alert admin@domain.com  include /etc/monit.d/*

Now to monitor Apache, create a file /etc/monit.d/httpd, enter

[root@superman ~]# vi /etc/monit.d/httpd

Add following content

check process httpd with pidfile /var/run/httpd.pid 

group apache  start program = "/etc/init.d/httpd start" 

stop program = "/etc/init.d/httpd stop"  if failed host 127.0.0.1 port 80 

protocol http then restart  if 5 restarts within 5 cycles then timeout

MySQL server restart configuration directives

check process mysqld with pidfile /var/run/mysqld/mysqld.pid 

group mysql  start program = "/etc/init.d/mysqld start" 

stop program = "/etc/init.d/mysqld stop"  if failed host 127.0.0.1 port 3306 

then restart  if 5 restarts within 5 cycles then timeout

SSH server configuration directives

check process sshd with pidfile /var/run/sshd.pid  start program "/etc/init.d/sshd start"  stop program "/etc/init.d/sshd stop"  if failed host 127.0.0.1 port 22 protocol ssh then restart  if 5 restarts within 5 cycles then timeout

Setup Monit Mail Alerts via SMTP: 

 set mailserver mail.yoursmtp.com, mail.foo.bar port 25 

 username "superman" password "binpip" using tlsv1, localhost 

 with timeout 15 seconds

Type the following command to start monit

[root@superman ~]# /etc/init.d/monit start

You can verify that monit is started from /var/log/monit.log log file:

[root@superman ~]# tail -f /var/log/monit.log  

Sample ouputs:

[IST June 17 14:51:18] info     : 'system_server2.domain.com' Monit started

To understand Monit config file better follow this link : http://mmonit.com/monit/documentation/monit.html
  
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