Today I got an e-mail in my inbox at work from a swedish company named Minicall that provide a beeper service. They started a new campaign to bring up the benefits of beepers called “Saving lifes is never out of date” (original swedish title “Rädda liv är aldrig omodernt”). Twenty years ago a lot of people used beepers instead of cellphones, today most people barely remember them and much less use them. Yet, these small devices for receiving a phone number or text messages from someone who wants to get in touch with you are lifesavers, literally speaking.

Most people today own a cellphone and use it on a regular basis, some people use only their cellphone and don’t even have a land-line phone at home. In the 90′s most people put their beepers in a box somewhere in the basement or garage, but some people didn’t and these people still use beepers. During a storm, a power outage or other emergency situation cellphones and land-line phones aren’t reliable enough, but the beeper never fails. Every day police force, firemen and hospital personnel use beepers to know when and where they are needed in case of an emergency situation, so literally speaking a beeper can save your life.

Why am I bringing this up on my blog about Linux and open source in enterprise environments? International and internet based companies are dependent on their IT-infrastructure to work 24/7 to provide information to offices all over the world or services for their customers. To meet these requirements you need staff in-house and on-call staff 24/7. In case of a power outage where a whole city turns black land-line phones and cellphone might get knocked out and in this situation you want to call in as much on-call staff you can get, but how? Beep them!

I’m on call at the moment and I carry a beeper everywhere I go, whenever they need me they beep and I can be at home sleeping as usual if everything works fine instead of spending the night at work. I want to remind you all about this great technology that makes beepers the most reliable way to send a message to someone and it’s importance in our every day life, whether we know it or not…

I’ve been using Nagios for system and network monitoring both at home and in an enterprise environment. At home i monitor services and hardware of two Linux servers and an IBM AS/400. Professionally I’ve been monitoring over 400 Linux-, Unix-, Mac- and Windows servers together with network devices such as switches, routers and load balancers.

Nagios is designed for Linux but should run nice on any *NIX system and requires a web server preferably Apache. Nagios monitors network services such as TCP, SMTP, POP, IMAP, HTTP, DNS, SSH, PING… etc. and host resources such as processor load, disk usage and number of users logged in. Nagios is also capable of host hierarchies for hosts and networks resources to detect network outages. The latest stable version of Nagios as I write this is Nagios 2.1.0 and latest development release is Nagios 3.0rc3.

Nagios is a scalable monitoring system that can have many nodes providing monitoring information to a central Nagios server with the web interface to present the collected information. In this case you set up the nodes to collect information through active and passive checks from the different hosts and network resources in your network and then sends then to a central Nagios server as passive checks. Except the web interface Nagios provides notifications of failing checks through e-mail, SMS or jabber with some 3rd party software eg. SMTP-server, SMS-gateway or Jabber-gateway.

The only inconvenience with Nagios is that the configuration is stored in text files. In large environment you end up with giant text files of configuration if you don’t create your own configuration file structure. Use of agents such as NRPE doesn’t really make your configuration file problem any smaller. To Nagios benefit I have to say that it’s fairly easy to write your own plugins, either for better functionality or to monitor your companies internally developed services.

During the time I’ve been using Nagios I have coded a few plugins for Nagios in Perl. Two of those plugins are remote checks of MySQL, first with a SELECT NOW() to check that it responds and the other check is of MySQL replication checking that replication is running and how many seconds behind the master it is. There are also two hard drive checks, one local using regular shell command df and the other check is a remote check using SNMP with the command snmpdf. These plugins can be found at: http://amelia.linuxchick.se/code/nagios-plugins/

For more information on Nagios and to download it visit http://www.nagios.org.

A screenshot of my Nagios running at home http://amelia.linuxchick.se/screenshots/nagios.jpg.