Homo-Adminus Blog

One of the main tasks of any administrator is to create stable environment for different sorts of businesses. Big part of this task is troubleshooting. There are many different tools in UNIX for system monitoring, but, at my mind, one of the most useful tools is lsof- one of the least-talked-about tools in a UNIX sysadmin’s toolkit. Lsof lists information about files opened by processes. But that’s really an understatement.

Most people forget that, in UNIX, (almost) everything is a file. The OS makes hardware available to applications by way of files in /dev. Kernel, system, memory, device etc. information in made available inside files in /proc. TCP/UDP sockets are sometimes represented internally as files. Even directories are really just files containing other filenames.

Lsof works by examining kernel data-structures and provides a variety of information related to files, pipes, sockets and more.

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Sometimes, especially if you have switched from some another GNU/Linux distribution to Debian GNU/Linux, your will have one major problem: you are missing some software available in your previous distribution. That is were Debian unofficial repositories can help you.

In this post I want to describe the most popular unofficial repositories with set of useful packages for my favorite Linux distribution - Debian .

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Today I dugg interesting site with not so many, but useful books about programming. There are 18 different sections all if which contains free books about some programming language.

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Red Hat company has recently opened its Knownedge Base - great collection of answers to frequently asked questions about linux systems. You no longer need to login to access it.

Red Hat Knowledgebase is a library of tips, troubleshooting advice, and current information updated daily by Red Hat technicians.

As for me, it is great news, because RHKB is one of the best libraries with information about linux systems.

Sometimes, when I speaking with Unix admins, I wondering, that they did not know anything about very useful UNIX tool - Screen window manager. That is why i decided to describe how I am using it in my job.

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Sometimes, I need to connect remote Unix servers with tunnels to provide some specific services or to get access to some internal networks. I was very surprised, when my friend, young system administrator, asked me about how to bring up IP-IP tunnel between different Unix operating systems (FreeBSD and Linux in his case) and said, that he can’t find information about this configuration. As the result of my discovering, this HOWTO has been created.

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Some times we need to debug some web-application or some web-server software, but we can not see complete HTTP-session. I very like Live Headers Plugin for Firefox, but it has some disadvantages… It can not say me when some interesting event happens.

Let me introduce very useful tool for web-server admins and web-developers: Fiddler - HTTP Debugging Proxy which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP Traffic, set breakpoints, and “fiddle” with incoming or outgoing data. Fiddler is designed to be much simpler than using NetMon or Achilles, and includes a simple but powerful JScript.NET event-based scripting subsystem.

If you need to debug HTTPS headers, you can use RPASpy plugin that enables viewing HTTPS request and response headers inside Fiddler.

Lewis Cunningham wrote very detailed article about Oracle Database 10g Express Edition (XE), about limitations of this version of Oracle and about specific areas where Oracle XE will be ideal solution.

Let me describe basic Oracle XE limitations:

• Memory - Oracle Database XE can address only 1GB of RAM.
• CPU - Oracle XE will only use one CPU.
• Instances count - Only one instance of Oracle XE can run on any given computer.
• Disk Space - You can only use up to 4Gb of disk space for your data.

At my mind, Oracle XE can be good replacement for poor MySQL database and slow PostgreSQL database servers in some areas. I’m using it in billing system of middle-sized ISP and I really glad to have possibility to use such powerful database for free.

Funny thing for admins from admins: Hot-Babe!

A small graphical utility which displays the system activity in a very special way. When the CPU is idle, it displays a dressed girl, and when the activity goes up, as the temperature increases, the girl begins to undress, to finish totally naked when the system activity reaches 100%.

There is even Windows port for Windows admins.

New day and new interesting link from one of the most valuable startups of year 2005 Digg.com! Today I dugg there link to very interesting List of Online Tools, Generators, Checkers for web-masters, web-developers, designers and other web-related professionals.

Let me provide to you set of most interesting things (as for me) from that list:

• Link Popularity Checker - The Link Popularity Checker tells you how many websites are linking to yours. Website popularity is an important factor in your search engine ranking. The more popular your site is, the better it will be ranked on the search engines.
• Favicon Generator - Use this online tool to easily create a favicon (favorites icon) for your site. A favicon is a small, 16×16 image that is shown inside the browser’s location bar and bookmark menu when your site is called up.
• 80×15 Brilliant Button Maker - This is a web interface to create “80×15 brilliant buttons”, you can also use two images (one on the left and the other on the right side) to decorate the button.
• HTTP Header Viewer - Use the form below to view the HTTP headers provided in response to the URL you provide. Useful debugging tool.
• mod_rewrite RewriteRule Generator - Our mod_rewrite RewriteRule generator will take a dynamic url given to it, and generate the correct syntax to place in a .htaccess file to allow the url to be rewritten in a spiderable format.
• E-Mail Icon Generator - For GMail, Hotmail, MSN, Yahoo!, AOL and many more!