Home » 2012 » March

Top 5 Linux Monitoring Tools. Web Based.

Monitoring (featured logo)

Linux system monitoring is one of the most important tasks for every sysadmin: it is crucial to know everything about system including CPU load, network traffic statistics, memory consumption, logged in users, availability of disk free space or service. And it’s inevitable that something breaks or goes down from time to time so usually it’s just better to know it happened from Linux monitoring system’s alert rather than from angry user. Believe me, it is true. In this article I’ve listed top 5 web based … Read more

Home » 2012 » March

Wget Cookies: Download Protected Content

command line

Most of Linux users are using wget from time to time, sometimes even when they don’t know about it – many GUI download managers for Linux are based on wget. Anyways wget is command line tool for downloading files over HTTP, HTTPs and FTP protocols within single session. It works like a charm with default settings for downloading simple static files, at the same time if content is protected by cookies and/or referrer then wget may seem useless but it’s actually not. For example, imagine … Read more

Home » 2012 » March

Fix socket timeouts in Nagios

Nagios (featured logo)

As any other monitoring system Nagios can produce false alarms. Usually it happens when Nagios fails to get the reply from the host being monitored during some pre-defined timeout. In order to mark service as down Nagios does three checks and if all of them are failed then the service is marked down and administrator will got an alert about its critical status. At the same time even if one of those checks fails Nagios will report administrator about it depending on configuration (e-mail, twitter, … Read more

Home » 2012 » March

Nfsen: Traffic Classification

Monitoring (featured logo)

Nfsen is open source sensor: it accepts netflow data from multiple netflow probes (servers, routers, vpn concentrators etc) and then visualizes it into human readable form. So using Nfsen you can see traffic statistics of every network device in your network in one place (actually Nfsen provides much more features).

By default Nfsen makes it possible to see only inbound and outbound traffic statistics but no protocol breakdown or any traffic classification. In the meantime it’s always useful to know what network applications are eating the bandwidth to understand if that fits baseline or not and take necessary actions. For example, if you’re monitoring Linux server which primary task is to host some website but in Nfsen you see that it generates 90% of SSH traffic and only 10% of web traffic then it would be reasonable idea to check if somebody is trying to brute force SSH password and stop that activity. In other words it’s better to have traffic statistics classified. In this article I’ll tell you how to enable traffic classification in Nfsen.

rrdgraph

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