Linux server administration

Webmin is a free and open source web-based control panel for managing a dedicated or virtual private server. Webmin works well for server administrators with intermediate as well as advanced level knowledge.

In this post I look at how to install Webmin on Centos Linux.

vnStat is a very simple utility that can track the amount of bandwidth used by your web server. It works by monitoring the received and transmitted bytes counters of your network interface and logging the data in a database. In this post I look at how to install vnStat and a web-based front end on a CentOS 5 Linux web server.

PHP is by far the most popular scripting language for dynamic web pages but it is not the most efficient language. Each time a PHP page is accessed it has to be:

• Parsed by the interpreter
• Converted into intermediary format called opcode
• Converted into machine code for your server's CPU to execute it
  

If the same script is accessed 100 times these steps are repeated a 100 times. To avoid this repetition and waste of server resources you can use the Alternative PHP Cache or APC.

APC is a PECL extension that caches frequently accessed PHP files code in opcode format for faster execution thereby reducing CPU load on your web server. In this guide I write about how to install and configure APC.

I have a centos 4.5 powered VPS that was running out of memory at peak times and so I decided to take a look at using squid to reverse proxy apache. When squid is used as a reverse proxy all http requests are proxied through squid to apache. The advantage of this setup is:

A cron job is a command that will run at a scheduled time. My website host allows me to set up cron jobs through the CPanel interface. Now I know I can use the serendipity backup plugin to do this but it only backups up the database to a directory on the server. IMO this does not serve much purpose since a backup should always be placed on a different system to the one being backed up. I think a simple approach is to email myself the backup. So I use a cron job to backup my database. Its a series of piped commands: