What is your favorite Linux monitoring application?

My favorite is nagios based opsview.

with zabbix you can monitor everything

I use zabbix and Orabbix to monitor Oracle

more info here: http://www.smartmarmot.com

I think that ZAbbix is now the most compresive tool

Big Brother -> Hobbit -> Xymon was our monitoring system of choice for almost 15 years, but it wasn't developing/updating as fast as we wanted.

Evaluated hyperic, nagios, etc -- lots of great benefits but just couldn't get them to be as easily extendable, manageable, reliable, and usable as we needed.

Transitioned to Zabbix a year ago and are confident that it will serve us well as our base of monitoring infrastructure for the next 10-15 years. Thank you Zabbix devs.

Open source is a very good alternative in this downturn period

Zabbix

Zabbix

https://mon.wiki.kernel.org/index.php/Main_Page
easy customizable with perl, small footprint

I'm surprised that Xymon/Hobbit isn't in the list of choices, it's definitely my first choice.

i used to use cacti + groundwork/nagios,the best combination :D

The recently released Zabbix version 1.8.2 is simply awesome.

For most part we use Zabbix and Munin
and we still have MRTG.

We started using Nagios several years ago and I have learned how to write custom
scripts to detect SAMBA login failures and shell login failures. It is great. The security
model is simple and near impossible to hack.

See my notes

rich

I chose to use this to monitor live servers and office systems back in 2005, I really liked the simple install, easy to write addon agents and remote collectors, the usefull graphics helped immensely to diagnose performance of jav virtual machines, memory, cpu and request rates.

We even had it send alerts via sms to operations when certain limits, events were triggered.

Can't understand why it never gets featured.

http://pandorafms.org/

Used for different things on networks e.g. Cacti for raw Bandwidth usage, Smokeping for WAN connectivity and alerting, Munin for host info and Monit for alerting host info, nTOP for local LAN data and OSSIM for IDS in a DMZ network.

I was looking for something simple. After some research I've chosen Munin which in fact is a graphing tool but already does some nice monitoring, too.
Monit I use where protocols and finer grading of alerts is needed.
netstat.php I wrote myself to have a simple "interface" (with red and green lights:) for my users + clients (something which I found even many of bigger solutions are lacking).

Mon has monitored my network for 13 years now, I think.

More a 'framework for scheduling monitoring activities and alerts'. A few lines of a script (usually perl) to return a 'this is working/failed' status, a script to generate alerts (via whatever mechanism you have... email, sms gateway, for a long while I had it dialing a numeric pager via modem), etc.

Simple and reliable, it's one of those packages that Just Works.

Zabbix FTW! 1.8.x branch is showing big improvements in stability, features, and php frontend

Simple and extendable.

Switched from Openview long, long ago. Switched from BB long ago. Switched from Nagios+Cacti a couple of years ago. Am quite satisfied with Zabbix now, though it's alerting subsystem is not up to Nagios it is otherwise much simpler and more powerfull. We write python + zabbix_get scripts to do alerting. Main drawback, other than alerts, is that it's written in PHP.

Second place has to go to OpenNMS which has most of the features of the others but none of the upgrade / security / integration hassles (thanks primarily to Java).

Xymon | Hobbit since... forever!