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… Read More »Top 5 Linux Monitoring Tools. Web Based.
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… Read More »Fix socket timeouts in Nagios
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.
Some time ago I found it pretty useful to configure Nagios monitoring system to send me a phone call in case of some critical problem. If some mission critical application goes down at night most probably you’ll miss an e-mail or sms notifying about that… Read More »Phone call as Nagios notification
Using nfsen it is possible to view IP traffic statistics on Linux interfaces including the graphs showing data sent and received (see the screenshot to the right) as well as historical information about all data transfers. So after you’ve configured nfsen and nfdump to monitor… Read More »Install nfdump and nfsen netflow tools in Linux
Today I’d like to describe setup of sendmail that allows to establish receiving of e-mails for certain domain and sort incoming messages between virtual users. Those users must be able to fetch received e-mails via POP3 or IMAP protocols with or without TLS encryption. The… Read More »Sendmail for virtual users with procmail, spamassassin and dovecot
It was long time ago when I wrote here last time but today I’d like to share the link to an application that would be appreciated by everyone starting from Linux starter wishing to speed up his/her Internet connection and ending with system administrators who… Read More »Namebench: cross-platform DNS benchmarking tool
By default Cisco IOS doesn’t provide any traffic monitoring tools like iftop or iptraff available in Linux. While there are lots of proprietary solutions for this purpose including Cisco Netflow Collection, you are free to choose nfdump and nfsen open source software to monitor traffic… Read More »How to monitor traffic at Cisco router using Linux (Netflow)
Recently I’ve bought WD TV media player for streaming full HD movies (primarily in 1080p resolution) to my home TV from external storage like usb HDD or ipod classic. You might already know that size of average HD movie rip is more than 4GB (e.g.… Read More »Split huge files in Ubuntu or any other Linux distro
Just came across smart ubuntu online radio client — radiotray. As it comes from its name radiotray sits in Ubuntu’s system tray and just plays online radio (see the screenshot taken on my Ubuntu Lucid Lynx). You can of course stop playing or select different… Read More »radiotray: online radio player for Ubuntu