How to set up a monit to monitoring server

Post Date: March 6, 2019
Last Updated: October 10, 2026

Introduction

This guide explains how to set up Monit to monitor a server. Monit is an open source tool that watches processes, files, directories, and system resources (CPU load, memory, swap, disk space). It can automatically restart a service that has stopped, or send you an alert when something goes wrong.

Typical uses include:

• Keeping services like Apache and sshd running
• Watching the system logging service
• Tracking system load, RAM, and swap usage
• Detecting when a service or port stops responding

Note: Monit doesn’t read hardware sensors such as motherboard temperature or physical disk health. Use a dedicated tool like smartmontools alongside it for that.

The steps below use CentOS/RHEL-style paths. CentOS 7 is past end-of-life, but the same steps work on AlmaLinux and Rocky Linux (use dnf in place of yum). On Ubuntu or Debian, install with apt install monit; the config lives in /etc/monit/monitrc.

Prerequisites

Before you set up Monit, make sure you have:

• A CentOS or RHEL-compatible server
• Root or sudo access
• Apache installed, if you want to follow the Apache example in Step 6

Architecture

• The Monit daemon runs in the background and runs every check you define at a fixed interval
• If a check passes, nothing happens. If it fails, Monit runs the action you chose, such as restarting the service or sending an alert
• A small web interface (port 2812) shows the status of everything Monit watches

The diagram below shows what happens once you set up Monit:

For every available check type and option, see the official Monit documentation.

Steps to Set Up Monit to Monitor a Server

1. Install Monit

To set up Monit on CentOS, enable the EPEL repository first, then install Monit:

sudo yum install -y epel-release
sudo yum install -y monit

Note: The original guide installed EPEL from a hardcoded rpm URL, but the URL had stray spaces in it (https: //dl.fedoraproject .org/...), so it would fail as written. Installing epel-release through your package manager avoids hardcoding a link that can go stale.

2. Start and Enable Monit

sudo systemctl enable --now monit

The original had a typo here: sytemctl instead of systemctl.

3. Verify Monit Is Running

sudo monit status

If it reports that it can’t connect to the daemon, the local web interface from Step 5 isn’t enabled yet.

4. Set the Check Interval

Open Monit’s main config file:

sudo vi /etc/monit.conf

Set how often Monit runs its checks (here, every 60 seconds):

set daemon 60

Note: The original mixed two different file names (/etc/monitrc and /etc/monit.conf). On CentOS/RHEL the config file is /etc/monit.conf. /etc/monitrc is the Debian/Ubuntu-style name.

Because this file can contain passwords, keep it readable only by root. Monit refuses to start if the file permissions are too open:

sudo chmod 600 /etc/monit.conf

5. Set Up Monit’s Web Interface Securely

When you set up Monit’s web interface, keep it on localhost unless you truly need remote access. Edit the existing set httpd block in /etc/monit.conf:

set httpd port 2812 and
    use address localhost
    allow localhost
    allow admin:YourStrongPasswordHere

To view it from your own machine, use an SSH tunnel and then open http://localhost:2812 in your browser:

ssh -L 2812:localhost:2812 user@your-server

If you genuinely need direct remote access, allow only your own IP address:

set httpd port 2812 and
    allow localhost
    allow 203.0.113.10
    allow admin:YourStrongPasswordHere

Security note: The original guide used allow 0.0.0.0/0.0.0.0 with the default login admin:monit. That exposes the interface to the entire internet with a publicly known password. Because the web interface can start and stop services, that’s a serious risk. Always set a strong password, restrict access by IP, and open port 2812 in your firewall only for those same IPs. The interface is plain HTTP unless you enable SSL, which is another reason to prefer the SSH tunnel.

6. Monitor Apache

Rather than editing the main config, create a separate file in /etc/monit.d/, which Monit loads automatically:

sudo vi /etc/monit.d/apache

check process apache with pidfile /var/run/httpd/httpd.pid
    start program = "/usr/bin/systemctl start httpd" with timeout 60 seconds
    stop program  = "/usr/bin/systemctl stop httpd"
    if failed host 127.0.0.1 port 80 protocol http then restart

Notes:

• The original used /etc/init.d/httpd scripts, which don’t exist on systemd-based CentOS 7+. Use systemctl as shown.
• The original also used curly “smart quotes” around the commands. Monit can’t parse those, so use straight quotes.
• On CentOS 7 the Apache PID file is /var/run/httpd/httpd.pid. The older /var/run/httpd.pid path was used on CentOS 6. Confirm yours with ls /var/run/httpd/. On Ubuntu it’s /var/run/apache2/apache2.pid.

7. Monitor rsyslog

sudo vi /etc/monit.d/rsyslog

check process rsyslogd with pidfile /var/run/syslogd.pid
    start program = "/usr/bin/systemctl start rsyslog"
    stop program  = "/usr/bin/systemctl stop rsyslog"

8. Set Up Email Alerts (Optional)

Once you set up Monit’s checks, alerts are what make it genuinely useful, because it tells you when something fails. If the server has a local mail service such as Postfix, add this to /etc/monit.conf:

set mailserver localhost
set alert admin@yourdomain.com

9. Test the Configuration and Reload

sudo monit -t
sudo monit reload
sudo monit summary

monit -t checks the syntax first, so a typo doesn’t leave you without monitoring. After the reload, monit summary should list apache and rsyslogd as running.

Conclusion

To set up Monit properly, install it from EPEL, keep the web interface locked down, put each check in its own file under /etc/monit.d/, and run monit -t before every reload. The commands that tend to trip people up are the typo’d systemctl, the broken EPEL URL, init.d scripts that don’t exist on newer systems, and a web interface left open with the default password.

Frequently Asked Questions

Can I set up Monit on Ubuntu? Yes. Install it with apt install monit. The main config is /etc/monit/monitrc, extra checks go in /etc/monit/conf.d/, and Apache’s PID file is /var/run/apache2/apache2.pid.

Do I need the web interface to set up Monit? Not for remote access, but keep the localhost interface enabled. Commands like monit status and monit summary use it to talk to the running daemon.

Why does my Apache check show “Does not exist”? Almost always a wrong PID file path. Check where your system actually writes it, as covered in Step 6.

How often should I set up Monit to run its checks? Every 30 to 60 seconds is common. Shorter intervals catch failures faster but add a little more load, so match the interval to how quickly you need to react.

Is it safe to keep the default admin:monit login? No. It’s a publicly known default. Replace it with a strong password before anything else.

Related Articles

Implementing Auditd for System Activity Monitoring in Linux Servers

Using PHP and Cron to Automate Kannel Status Monitoring

Talk to Our Technology Experts

Need reliable monitoring and alerting for your servers? Our team can help with server monitoring, uptime alerting, and ongoing infrastructure support.

Connect with our technology experts.