WRT Router Series Monit

This subject could apply to installations on other platforms besides OpenWRT.

Monit allow for monitoring (via command line or web GUI (http://WhatEverIPAddressOrHostName:2812 (default port))) of services, plus restarting of services if they're not running or not responding.

Installation

opkg update

opkg install monit

Configuration File(s) & Directories for Monit Service

/etc/monitrc (file)

/etc/monit.d (directory)

If configuring in a fashion similar to operating systems such as CentOS, then;

• Create this Directory: /etc/monit.d
• Add this line or un-comment this line from /etc/monitrc: include /etc/monit.d/*
• Add additional configuration files to the /etc/monit.d Directory

Configuration

The default configuration for Monit from OpenWRT is configured in a very secure, with limited capability to view information (IE, it's only available from the command line, see the below configuration section from /etc/monitrc);

set httpd port 2812 and
    use address localhost  # only accept connection from localhost (drop if you use M/Monit)
    allow localhost        # allow localhost to connect to the server and
    allow admin:monit      # require user 'admin' with password 'monit'

The above configuration does not allow for remote viewing via a web browser. But the below configuration allows for a reasonably secure configuration for viewing via a web browser (not including HTTPS, since it is a Local Area Network)

set httpd port 2812 and
    use address W.X.Y.Z     # IP Address that the Monit Web Services "listens" on
    allow W.X.Y.0/24        # IP Address Range that the Monit Web Service allows connections from
    allow WhatEverUserName:WhatEverPassword

Configuration of Individual Service(s) Monitoring

If configured in the manner described in the Configuration File(s) for Monit Service section, each of the following example can be placed in a separate text file in the /etc/monit.d directory.

Apache Example (The below Apache example is very simple. It can also be configured to connect to a website and check for the existence of a specific file);

check process httpd with pidfile /tmp/run/apache2/httpd.pid
start program "/etc/init.d/apache2 start"
stop program "/etc/init.d/apache2 stop"
restart program "/etc/init.d/apache2 restart"
if 5 restarts within 5 cycles then timeout

BIND / NAMED Example;

<syntaxhighlight lang="text">
check process named with pidfile /tmp/run/named/named.pid
start program "/etc/init.d/named start"
stop program "/etc/init.d/named stop"
restart program "/etc/init.d/named restart"
if failed host 192.168.2.1 port 53 type tcp protocol dns then restart
if failed host 192.168.2.1 port 53 type udp protocol dns then restart
if 5 restarts within 5 cycles then timeout

DHCPC Example; check process dhcpd with pidfile /tmp/run/dhcpd.pid start program "/etc/init.d/dhcpd start" stop program "/etc/init.d/dhcpd stop" restart program "/etc/init.d/dhcpd restart" if failed host 192.168.2.1 port 67 type udp then restart if 5 restarts within 5 cycles then timeout </syntaxhighlight> MySQL Example;

check process mysqld with pidfile /tmp/run/mysqld/mysqld.pid
start program "/etc/init.d/mysqld start"
stop program "/etc/init.d/mysqld stop"
restart program "/etc/init.d/mysqld restart"
if failed unixsocket /tmp/run/mysqld/mysqld.sock then restart
if 5 restarts within 5 cycles then timeout

Notifications & Alerts

The Monit service can also send email notifications and alerts. This can get annoying over time, but it is useful if troubleshooting or monitoring a process. The annoyance can also be "reigned in" to a certain degree.

Some Interesting HDD / SSD Monitoring Tips

From: https://www.smarthomebeginner.com/monit-monitor-hard-drive-smart-health-and-temperature/

And to monitor via UUID instead of "SDx" (which is a bit unreliable): https://wiki.archlinux.org/index.php/S.M.A.R.T.

Additional Tips

For monitoring OpenVPN: https://serverfault.com/questions/647506/make-monit-check-openvpn-client-connection-status

Finally / Lastly

...and of course after configuring a new MONIT file, restart the service: service monit restart

Credits & Thanks

A lot of information from here (not sure if this is the original source, but crediting just the same): https://www.smarthomebeginner.com/monit-monitor-file-server-status-samba-nfs/