Today we are going to learn that how to Install Monit on Centos 8. Before proceeding further let’s have a short introduction about Monit.
What is Monit?
Monit is an Open Source process tracking tool for Linux OS that helps you to monitor the processes by system. When the process is going down, it robotically does the preservation and restore that specific process and guarantees it is introduced again on-line.
Monit also can be used for handling and monitoring of packages, files, directories, filesystems, TCP/IP network exams, protocol assessments, and can make use of SSL for such tests. So, follow the below steps for an easy and smooth installation of Monit on your system.
Step 1: Update System
Update your system by running
sudo yum update -y
And install the required tools by typing
sudo dnf install -y git gcc glibc make glibc-devel kernel-headers autoconf automake libtool bison flex libzip-devel pam-devel openssl openssl-devel
Step 2: Clone Monit
Fire the below command to clone the source code of Monit for compiling
git clone https://bitbucket.org/tildeslash/monit.git
After this run the given commands step by step to Compile the Monit.
cd monit
./bootstrap
./configure
make
make install
Step 3: Configuring Monit Functionality
First of all copy the monitrc file we’ve downloaded above to the /etc directory
sudo cp monitrc /etc/
Then edit that file using any editor you prefer.
sudo nano /etc/monitrc
And apply the few changes as below
Provide the time interval that required for the process checking by Monit. Modify it by changing the line
set daemon 30
Provide the email server to get notified about the alerts in your inbox.
set mailserver mx.osradar.local port 25
Note: You can also customize the alert templates. For doing so modify the configuration file.
Now, change the log setting by running
set log /var/log/monit.log
And don’t forget to change uncomment the given line
include /etc/monit.d/*
Step 4: Configuring Monit Web Interface
Monit also provides the Web Interface to monitor and manage the configured services with the Monit. By default, it listens to the port 2812. To configure the web interface edit the /etc/monitrc file with your favorite editor.
sudo nano /etc/monitrc
Then moderate the below entries
From
To:
By doing these setting, Monit will be able to listen to all the interfaces on port 2812. Only the administrator will be able to access the Web based dashboard.
Step 5: Configuring Systemd For Monit
As to start Monit automatically on boot, create a new configuration file for systemd
sudo nano /lib/systemd/system/monit.service
Then paste the below data into the file
This file is systemd template for monit service. To
# register monit with systemd, place the monit.service file
# to the /lib/systemd/system/ directory and then start it
# using systemctl (see below).
#
# Enable monit to start on boot:
# systemctl enable monit.service
#
# Start monit immediately:
# systemctl start monit.service
#
# Stop monit:
# systemctl stop monit.service
#
# Status:
# systemctl status monit.service
[Unit]
Description=Pro-active monitoring utility for unix systems
After=network.target
Documentation=man:monit(1) https://mmonit.com/wiki/Monit/HowTo
[Service]
Type=simple
KillMode=process
ExecStart=/usr/local/bin/monit -I
ExecStop=/usr/local/bin/monit quit
ExecReload=/usr/local/bin/monit reload
Restart = on-abnormal
StandardOutput=null
[Install]
WantedBy=multi-user.target
Then reload the systemd daemon
sudo systemctl daemon-reload
And start & enable the systemd services.
sudo systemctl start monit
sudo systemctl enable monit
Step 6: Allow Firewall Access
Give permissions Monit web interface through firewall by typing
firewall-cmd --permanent --add-port=2812/tcp
firewall-cmd --reload
Step 7: Accessing Monit Web Dashboard
Go to your browser & type 127.0.0.1:2812/
Provide the credential details as admin admin (or use whatever you’ve given in step 4).
Then click on the OK button and you will be redirected to the Homepage of Monit.
Here you can see the configured services.
Step 8: Configuring Services with Monit for Monitoring & Managing
First of all create a new directory
sudo mkdir /etc/monit.d/
Then configure the services for syslog
sudo nano /etc/monit.d/syslogmonitor
And paste the below info.
check process SysLog with pidfile /var/run/rsyslogd.pid
start program = "/usr/bin/systemctl start rsyslog.service"
stop program = "/usr/bin/systemctl stop rsyslog.service"
Edit the file /etc/monit.d/httpdmonitor for configuring the HTTP services.
sudo nano /etc/monit.d/httpdmonitor
And modify the changes like this
check process HTTPD with pidfile /var/run/httpd/httpd.pid
start program "/usr/bin/systemctl start httpd.service"
stop program "/usr/bin/systemctl stop httpd.service"
if failed port 80 protocol http then restart
After doing all these settings, verify the Monit syntax by
monit -t
Now, reload the Monit to take the effect of changes.
sudo systemctl reload monit
Now, again go to the Web Dashboard to see if the services, we’ve configured are showing.
When you click on the any listed service, it will give you the information in details.
Here you can perform various functions like start, stop, restart or disable these services.
Step 9: Testing the Monitoring
First of all stop the http service for testing purposes.
sudo systemctl stop httpd
After 30s type this command to check the logs
cat /var/log/monit.log
Ouput:]
EDT Mar 19 13:01:49] error : 'HTTPD' process is not running
[EDT Mar 19 13:01:49] info : 'HTTPD' trying to restart
[EDT Mar 19 13:01:49] info : 'HTTPD' start: '/usr/bin/systemctl start httpd.service'
Type the command to edit the configuration
sudo nano /etc/monitrc
Set the alert template like this according to your requirements.
set mail-format {
from: Monit
subject: monit alert -- $EVENT $SERVICE
message: $EVENT Service $SERVICE
Date: $DATE
Action: $ACTION
Host: $HOST
Description: $DESCRIPTION
Your faithful employee , monit
}
Now, set the recipient address to get notified of all actions.
set alert root@localhost
And set the recipient address for not alerting on user initiated service restarts.
set alert root@localhost not on { instance, action }
Then finally, set up the email server in order to receive emails.
set mailserver localhost
As I’ve installed the local relay in order to read email from terminal you can also do so or set up your own email server.
dnf install -y sendmail && systemctl start sendmail
Reload the services
sudo systemctl reload monit
Now, you can see the email alerts by running
cat /var/spool/mail/root
You can also install the mutt, an email client to view alerts by running
dnf install -y mutt
So, this is how you can Install Monit on Your CentOS system and easily Monitor and Manage the process.
