Monitor and Manage your services with Monit on CentOS 6 / RHEL 6

Monit

Monit is an opensource process tool for Linux operating system which helps you to monitor system process using web browser and also when ever requires it automatically do the maintenance or repair of particular process in such a way that it can be brought back online. It can also used for managing and monitoring of programs, files, directories, and devices for timestamps changes, checksum changes, or size changes; not limited to perform various TCP/IP network checks, protocol checks, and can utilize SSL for such checks.

It logs to its own log file and notifies the user via customizable messages, this guide will help you to setup monit on CentOS / RHEL.

Configure EPEL repo to download the latest Monit package.

[root@server ~]# rpm -Uvh http://epel.mirror.net.in/epel/6/i386/epel-release-6-8.noarch.rpm

Install the Monit.

[root@server ~]# yum -y install monit

Start monit by using the following command.

[root@server ~]# monit

Check the monit status.

[root@server ~]# monit status
The Monit daemon 5.1.1 uptime: 0m
 
System 'server.itzgeek.com'
status                            running
monitoring status                 monitored
load average                      [0.12] [0.11] [0.09]
cpu                               91.6%us 8.3%sy 0.0%wa
memory usage                      727512 kB [71.8%]
data collected                    Mon Jul  7 07:51:09 2014

Configure Monit:

Monit conig file is /etc/monit.conf, by default monit is set to check the services at interval of 2 min, this setting can be altered by changing.

[root@server ~]# vi /etc/monit.conf
set daemon  120

Alert cans be configured by.

set mailserver

Alert templates can be found in the configuration file itself.
Logs setting can be changed by using the following file.

[root@server ~]# vi /etc/monit.d/logging
 
set logfile

Web Interface:

Monit also provides a web interface to monitor and manage the configured services, by default monit listens on 2812 port but it needs to be setup. Open monit configuration file /etc/monit.conf.

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

Look for httpd port 2812, uncomment the line.

set httpd port 2812
allow 0.0.0.0/0.0.0.0
allow admin:admin

From the above settings, monit will listen on 2812; admin user will able to access the web interface from any network.

Reload monit.

[root@server ~]# /etc/init.d/monit restart

Access the web interface by using http://your-ip-address:2812, use the username and password mentioned in the previous step. Monit home page will look like this.

Monit Home Page
Monit Home Page

Configuring services for monitoring:

Once the web interface is up, we can start to setup other services that you want to monitor; you can place the configuration files under /etc/monit.d/ directory.

Configure for sshd.

[root@server ~]# vi /etc/monit.d/sshdmonitor
 
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 port 22 protocol ssh then restart

Configure for syslog.

[root@server ~]# vi /etc/monit.d/syslogmonitor
 
check process syslogd with pidfile /var/run/syslogd.pid
start program = "/etc/init.d/rsyslog start"
stop program = "/etc/init.d/rsyslog stop"

Once configured, test the monit syntax

[root@server ~]# monit -t
 
Control file syntax OK

Reload configuration fie to take effect of changes.

[root@server ~]# monit reload

Access the web interface, you would find the new services that we configured earlier.

Monit With Configured Services
Monit With Configured Services

Test the Monitoring:

Now stop the syslog daemon.

[root@server ~]# /etc/init.d/rsyslog stop

Wait for 30 second, monit will start the syslog automatically. You can find it in monit log.

[root@server ~]# cat /var/log/monit
[IST Jul  7 08:50:27] error    : 'syslogd' process is not running
[IST Jul  7 08:50:27] info     : 'syslogd' trying to restart
[IST Jul  7 08:50:27] info     : 'syslogd' start: /etc/init.d/rsyslog
[IST Jul  7 08:51:28] info     : 'syslogd' process is running with pid

That’s All, We have successfully configured Monit on CentOS 6 / RHEL 6. We welcome your feedback, please post your valuable comments below.

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