I did not get any feed back on my first nagios episode, so I can only assume that I perfectly explained what nagios is. And my installation instructions were so good, that no one had any questions. So I will move on to some additional nagios topics.

Why use nagios

One thing I meant to talk about but forgot in the intro is why you may want to run nagios as a hobbyist.

Education, learning a new technology for fun

Network Monitoring is a valuable skill and benefit your career if you work in IT

Early warning for failing hardware

Monitoring self hosted applications

Notification for home security devices IP cameras

Most of the benefits of nagios are not specific to nagios. There are plenty of other options for monitoring, and all of them are worth exploring.

Notification Options

Email

I had planned on discussing how to set up postfix to send emails. But, that is such a big topic I will have to skip it. I will instead talk about what I do to send email. And Maybe you can do something similar.

Spammers have ruined the ability to directly send email. Most residential ISPs block port 25 outbound to prevent malware from sending email. Some Virtual hosting providers may not block sending mail, but many mail servers will not accept mail from VPS IP ranges.

There are a few ways to get around this problem. I use the email delivery service Sendgrid. They do all the work of staying off the list of spammers, and most email providers trust mail send via Sendgrid.

I wont go into the instructions for configuring postfix to relay outgoing mail via Sendgrid, but their documentation is easy to follow.

There are plenty of services like sendgrid. And most have a free tier. So unless you are blasting out alerts you probably will not have to pay. If you want to send alerts from nagios via email, I recommend finding a email sending service that works for you.

Push alerts

There are a few options (besides email) for getting alerts on your phone.

aNag

The easiest way to get alerts is probably the aNag Android app. aNag connects to the nagios UI to get status updates. It can be configured to check in periodically and there generate notifications for failed checks.

One downside to aNag is the phone has to be able to connect to the nagios server. So, if nagios is on a private network, you will need a VPN when you are not on the same network.

If you decide to put nagios on a public network, be sure to configure apache to only use HTTPS. certbot makes this really easy.

Pushover

Another option is to us a Push Notification service that can send notifications that are triggered by API calls.

I like to use the pushover.net You pay $5 when you download the pushover app from the app store, and then notifications are sent for free. They offer a 30 day trial if you want to evaluate the service.

To use pushover, we will add a new contact to nagios. The command for the pushover contact is a script that calls the pushover API via curl.

Remember from the previous episode, nagios has a conf.d directory and will load any files in that directory. So we will create a new file /etc/nagios4/conf.d/pushover.cfg and restart nagios. The contents of the pushover file will be in the show notes.

To use pushover for specific checks, and the contact to that check. See the example in the show notes. Or if you want to use pushover for everything Modify the definitions for the host and service templates to use pushover as a contact

The script that calls the Pushover API is at https://github.com/jedda/OSX-Monitoring-Tools/blob/master/notify_by_pushover.sh Save a