Auto-registering Linux agents with TLS PSK encryption

Zabbix supports Linux agent auto-registration and it’s a well documented process in the Zabbix manual. However, it’s not really straightforward to mass provision Zabbix agents on hundreds of servers if you want to have Zabbix agent <-> Zabbix server communication encrypted. At least not without some form of additional scripted step in your installation process. For large deployments I usually use Ansible, although this article just briefly covers that part and I’ll mostly focus on how to make sure your agents get registered for encrypted communication.

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Create your own items – extend the agent with userparameters

Zabbix supports many different ways of monitoring, including agentless, SNMP and IPMI. Zabbix also provides a monitoring agent, which has a great set of built-in items for monitoring diskspace, processes, memory usage and many other things.

While the list of built-in items is growing with each release, there will always be something else we will want to monitor. Luckily, Zabbix agent is very easy to extend with new items by using a feature called userparameters. Zabbix userparameters are commands that the agent runs and expects an item value to be returned.

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These are not the applications you are looking for

Applications – software applications – mean a specific thing in IT. Usually, that’s a user-oriented piece of software. A web browser, word processor, game. Lately, mobile applications have somewhat lowered the bar, even down to I Am Rich applications.

Screenshot of the "I Am Rich" application, showing the price of USD 999.99
“I Am Rich” sale screen (https://en.wikipedia.org/wiki/File:I_Am_Rich_sale_screen.png)

And then there’s Zabbix with it’s own definition for applications. So what are applications in Zabbix?

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Still wondering about missing notifications in 2017?

If Zabbix keeps on surprising you with its notifications, you might want to try the Action Simulator! The Action Simulator is a community patch that helps you to figure out whether your actions really do as you intend. It first came out for Zabbix 2.0 in 2013 and was downloaded by hundreds of users from all around the world.

The following article gives a brief introduction to the Action Simulator and explains the challenges of developing it for Zabbix 3.2.

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Zabbix – Why You No Audit?

Testing of new Zabbix items, triggers, actions, etc is always easier on a separate test instance, which is the reason why we have a few test Zabbix servers. These test servers are usually behind our firewall, but a few weeks ago we found that one test instance wasn’t. To make things even worse, it had the default admin credentials.  This wasn’t a big issue, because it was isolated from the rest of our hosts, but it was interesting what happened on that server.

The way we found out that the server was compromised was that it was using 100% CPU. The process which was using all the CPU was a process which we never seen before, nor did any of us ever configure it, and of course it was run by the zabbix user. We killed it instantly, and after some digging around we found out that the executable file was used as an agent for some data mining service on which you can rent computing power to do some tasks.

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Zabbix bug TOP20, March 2017

Let’s talk bugs. The important Zabbix bugs. What are those? The ones that have the most votes in the Zabbix issue tracker.

TOP3 Zabbix bugreports from the table below in the article

There are currently 1308 open bugreports. When we looked at this number back in November last year, it was a hundred less. That’s a pretty huge number, is everything bad? Not really, as some might be duplicates and some might be incorrect reports. Not many, though, as there’s constant grooming going on. Most of the remaining are valid bugreports, but not too critical – some are even as minor as an offset of a few pixels in some page. Still a bug, but something we can live with, mostly. We already looked at the top-voted bugreport, now is the time to glance at others same as we did with feature requests.

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The most important bug in Zabbix

How do you determine which bugs are important ?

The bug must be still unfixed to be important. If a new version of Zabbix comes out and the server crashes for all the users, that is the most important bug. Until it is fixed, hopefully, soon.

But there are some long-standing bugs that linger around just below the “fix-it” surface – they’re  not terrible enough to be fixed right away, and somewhat complicated usually. Such bugs can be around for many years, sometimes not even being fixed, but going away because a feature gets dropped completely. We’d need a way to measure which of all those known bugs is the most important. And there is a way to find out – same as with features, users can vote on bugreports. The bugreport with the most votes is titled deadlock between server and frontend.

Jira screenshot, showing "deadlock between server and frontend" issue title

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Created a trigger and it disappeared? Read on for a revelation!

So you had a cluster monitored. As is common with clusters, you wanted to have some cluster-wide parameter adding. Average CPU load, number of nodes online – something not tied to a single cluster node, thus you created a special host to denote the whole cluster. Then you went to that host, clicked “Create trigger”, specified all the items on individual cluster hosts, clicked “Add”… and the trigger was not there. Mysteriously missing.

An empty Zabbix trigger list with a red "NO TRIGGERS" text added

Oh, wait. That trigger actually appeared on all the cluster hosts. Is this a bug?

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Visiting the Open Source Monitoring Conference 2016, Part 4

Returning to the events of the Open Source Monitoring Conference 2016, Avishai Ish-Shalom discussed an engineer’s approach to monitoring. David Hustace from OpenNMS told positive stories about this true-opensource monitoring tool.

OpenNMS mascot with a t-shirt saying "The kiwi bird is a direct descendant of the tyrannosaurus rex. rawr."

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Zabbix stopped sending out alerts, HALP!

Zabbix was this reliable friend, always sending you an email, SMS or both when something went down. It sometimes sent you a lot of emails, but you never got angry at Zabbix about that – it was just eager to help you, make sure you did not miss the weekly disaster. But then… last week… Zabbix did not send you an SMS. It did not send you an email. It did not telepathically inform you. But things were DOWN. Server was not RESPONDING.

A fat cat at a table with paws up

Zabbix knew about this. As you review the data, sitting in a dark room, the graphs clearly show the downtime. But there was-no-alert. How is that possible? Wait, what, this is impossible. You can see on the glowing screen that the main action, a crucial piece in getting those alerts, is disabled. That just cannot be, as nobody, NOBODY would ever disable that. How, oh how. Why, oh why.

Zabbix frontend row, showing a disabled action

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