nixCraft

This is a Linux sys admin journal by Vivek about sys admin work, Linux tips & tricks, hacks, news and more.

URL: http://www.cyberciti.biz/

Updated: 7 hours 39 min ago

Leap Second To Be Added End Of 2008 And Its Impact On Clustered Computers / Network

Wed, 12/31/2008 - 20:28

Get ready for a minute with 61 seconds. Scientists are delaying the start of 2009 by the first 'leap second' a timing tweak meant to make up for changes in the Earth's rotation.

The aged Earth is slowing down in its daily rotation, at least in the current epoch. So a leap second is added (a one-second adjustment added) to our time. This year will be exactly one second longer.

Precise time measurements are needed for high-speed communications systems among other modern technologies such as clusters, GPS, networks. You need to make sure that you are running updated version of ntpd that support leap second for UNIX and Windows computers.

XEN Virtualization Set The MTU For xenbr0 Interface

Wed, 12/31/2008 - 18:40

I've already written about setting the MTU (Maximum Transmission Unit) under Linux including Jumbo frames (FreeBSD specific MTU information is here).

With this quick tip you can increase MTU size to get a better networking performance.

SELinux Apache Allow To Serve The Contents Of a Loopback Mounted ISO Image

Wed, 12/31/2008 - 18:11

Q. How do I configure CentOS Linux SELinux security to permit httpd 2.2 (Apache web server) to serve the contents of a loopback mounted ISO images located at /var/www/html/lan/iso directory?

Answer to "SELinux Apache Allow To Serve The Contents Of a Loopback Mounted ISO Image"

Top 10 Linux Virtualization Software

Wed, 12/31/2008 - 15:00

Virtualization is the latest buzz word. You may wonder computers are getting cheaper every day, why should I care and why should I use virtualization? Virtualization is a broad term that refers to the abstraction of computer resources such as:

Platform Virtualization
Resource Virtualization
Storage Virtualization
Network Virtualization
Desktop Virtualization

This article describes why you need virtualization and list commonly used FOSS and proprietary Linux virtualization software.

Apache2 mod_fastcgi: Connect to External PHP via UNIX Socket or TCP/IP Port

Tue, 12/30/2008 - 12:49

Now, mod_fastcgi is configured and running. FastCGI supports connection via UNIX sockets or TCP/IP networking. This is useful to spread load among various backends. For example, php will be severed from 192.168.1.10 and python / ruby on rails will be severed from 192.168.1.11. This is only possible with mod_fastcgi.

Red Hat / CentOS Apache 2 FastCGI PHP Configuration

Tue, 12/30/2008 - 10:31

FastCGI is a protocol for interfacing interactive programs with a web server. FastCGI's main aim is to reduce the overhead associated with interfacing the web server and CGI programs, allowing a server to handle more web page requests at once.

Also, PHP is not recommended with multithreaded Apache2 (worker MPM) because of performance and some 3rd party PHP extensions are not not guaranteed thread-safe.

nginx and lighttpd has inbuilt support for FastCGI. For Apache web server you need to use either mod_fastcgi or mod_fcgid.

mod_fastcgi allows server and application processes to be restarted independently -- an important consideration for busy web sites. It also facilitates per-application security policies -- important for ISPs and web hosting companies.

In this quick tutorial, you will learn about Apache 2 + mod_fastcgi + PHP installation and configuration under Red Hat Enterprise Linux / CentOS Linux version 5.x+.