Monit is a free, open-source process supervision tool for Unix and Linux. With Monit, system status can be viewed directly from the command line, or via the native HTTP web server. Monit is able to do automatic maintenance, repair, and run meaningful causal actions in error situations.
In this guide we will learn how to install and configure monit on a Rocky Linux 8 server. If you are interested in setting up M/Monit, checkout How to install and set up M/Monit in Linux.
These are some of the features of Monit.
Monit can act if an error situation should occur, e.g.; if sendmail is not running, Monit can start sendmail again automatically or if apache is using too much resources (e.g. if a DoS attack is in progress) Monit can stop or restart apache and send you an alert message. Monit can also monitor process characteristics, such as; how much memory or cpu cycles a process is using.
You can use Monit to monitor daemon processes or similar programs running on localhost. Monit is particularly useful for monitoring daemon processes, such as those started at system boot time from /etc/init/ For instance sendmail, sshd, apache and mysql.
Files, Dirs and Filesystems
You can also use Monit to monitor files, directories and filesystems on localhost. Monit can monitor these items for changes, such as timestamps changes, checksum changes or size changes. This is also useful for security reasons – you can monitor the md5 or sha1 checksum of files that should not change and get an alert or perform an action if they should change.
Cloud and Hosts
Monitor network connections to various servers, either on localhost or on remote hosts. TCP, UDP and Unix Domain Sockets are supported. Network tests can be performed on a protocol level; Monit has built-in tests for the main Internet protocols, such as HTTP, SMTP etc. Even if a protocol is not supported you can still test the server as you can configure Monit to send any data and test the response from the server.
Programs and scripts
Monit can be used to test programs or scripts at certain times, much like cron, but in addition, you can test the exit value of a program and perform an action or send an alert if the exit value indicates an error. This means that you can use Monit to perform any type of check you can write a script for.
Finally, Monit can be used to monitor general system resources on localhost such as overall CPU usage, Memory and Load Average.
Step 1: Installing Monit
Monit is available in the default Rocky Linux repositories. Use this command to install?
sudo dnf install -y monit
If you want to install the latest version, use the downloads page here.
Step 2: Starting and enabling service
Once installed, we need to start the monit service. Use this command to start:
sudo systemctl start monit
Check the status to confirm that the service is running using this command:
$ sudo systemctl status monit ● monit.service - Pro-active monitoring utility for unix systems Loaded: loaded (/usr/lib/systemd/system/monit.service; disabled; vendor preset: disabled) Active: active (running) since Thu 2022-03-31 15:37:35 UTC; 6s ago Docs: man:monit(1) https://mmonit.com/wiki/Monit/HowTo Main PID: 251683 (monit) Tasks: 2 (limit: 23465) Memory: 2.1M CGroup: /system.slice/monit.service └─251683 /usr/bin/monit -I Mar 31 15:37:35 monitoring systemd: Started Pro-active monitoring utility for unix systems.
Finally, enable monit on boot:
sudo systemctl enable monit
Step 3: Configuring monit service
Enable monit web interface
Monit comes with user friendly-web interface to view the system status and manage them through the web browser. By default, Monit web interface is disabled. You can enable it by editing /etc/monit/monitrc configuration file:
sudo vim /etc/monitrc
Make the following changes. The allow directive will require user ‘admin’ with password ‘monit’ for the web login.
set httpd port 2812 allow admin:monit
Set up M/Monit host
M/monit provides a central view of all mmonit data. It is helpful when you are managing muliple servers and do not want to login to each of them to check the status. The format of the url is
Use this command in monitrc to configure mmonit host:
set mmonit http://monit:[email protected]:8080/collector
Final monit configuration
set daemon 30 set log syslog set idfile /var/.monit.id set statefile /var/.monit.state set eventqueue basedir /var/lib/monit/events slots 100 set httpd port 2812 and use address 10.2.11.10 #only accept connection from localhost allow 0.0.0.0/0.0.0.0 allow admin:monit set mmonit http://monit:[email protected]:8080/collector include /etc/monit.d/*
Restart mmonit to apply changes
Save the file, then restart Monit service to apply the changes:
sudo systemctl restart monit
Step 4: Allow service through firewall
If you have firewalld installed and enabled, use this command to whielist monit port for external access.
sudo firewall-cmd --permanent --add-port=2812/tcp sudo firewall-cmd --reload
Step 5: Accessing the web interface
Open your web browser and type the URL
http://[your_servr_ip]:2812. You will be redirected to the Monit login page. Provide monit username as admin and password as monit, then click on the Sign In button. You should see the Monit default dashboard.
Step 6: Configure monit for a service with pid
include /etc/monit.d/* in the file
/etc/monitrc includes all defined configurations in monit.d directory. It is recommended to include individual configurations there.
We will use grafana-server as a example. We will need to create the configuration file for grafana-server. You can do this with the following command:
sudo vim /etc/monit.d/grafana-server
Then add this content:
check process grafana-server with pidfile /var/run/grafana/grafana-server.pid start program = "/bin/systemctl start grafana-server" with timeout 15 seconds stop program = "/bin/systemctl stop grafana-server" if failed port 3000 protocol http then restart
Next, verify the Monit status with the following command:
$ sudo monit -t Control file syntax OK
After resolving any possible syntax errors, you can start running all of the monitored programs.
monit start all
Next, restart the Monit service to apply the changes:
sudo systemctl reload monit
You can see the new service on the Monit web interface. Or you can use the status command in the terminal:
$ sudo monit status Monit 5.30.0 uptime: 12h 18m Process 'grafana-server' status OK monitoring status Monitored monitoring mode active on reboot start pid 43609 parent pid 1 uid 989 effective uid 989 gid 986 uptime 22d 11h 11m threads 11 children 0 cpu 0.0% cpu total 0.0% memory 2.7% [102.2 MB] memory total 2.7% [102.2 MB] security attribute system_u:system_r:unconfined_service_t:s0 filedescriptors 13 [0.1% of 10000 limit] total filedescriptors 13 read bytes 216.2 B/s [770.4 MB total] disk read bytes 0 B/s [2.3 MB total] disk read operations 2.1 reads/s [4070127 reads total] write bytes 24.8 B/s [331.1 MB total] disk write bytes 136.5 B/s [167.5 MB total] disk write operations 1.8 writes/s [3258928 writes total] port response time 1.485 ms to localhost:3000 type TCP/IP protocol HTTP data collected Fri, 01 Apr 2022 03:57:26 System 'monitoring' status OK monitoring status Monitored monitoring mode active on reboot start load average [0.04] [0.02] [0.00] cpu 1.1%usr 0.6%sys 0.0%nice 0.0%iowait 0.2%hardirq 0.1%softirq 0.1%steal 0.0%guest 0.0%guestnice memory usage 1.1 GB [31.1%] swap usage 0 B [0.0%] uptime 22d 13h 10m boot time Wed, 09 Mar 2022 14:47:17 filedescriptors 2496 [0.7% of 374156 limit] data collected Fri, 01 Apr 2022 03:57:26
Step 7: Monitor local system
We can also use monit to monitor and alert on local system resource usage. This file monitors for load average, memory, swap and cpu usage and alerts on thresholds defined.
check system $HOST if loadavg (1min) > 10 then alert if loadavg (5min) > 2 then alert if memory usage > 75% then alert if swap usage > 25% then alert if cpu usage (user) > 70% then alert if cpu usage (system) > 30% then alert if cpu usage (wait) > 20% then alert
Congratulations! You have successfully installed Monit monitoring tool on your rocky linux server.
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