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Beware of unforeseen differences between Unix and Linux

When it comes to migration, the differences between Unix and Linux matter most. Do you know the small and large changes to expect when you migrate?

With Linux rapidly replacing Unix on server platforms, Unix veterans may find the differences between Unix and Linux are hard to get used to.

The philosophy behind any Unix version is that the vendor takes complete care of its customers. Unix makes software available as a proprietary tool to guarantee its integrity. The Linux philosophy is that everything is open source; the source code of drivers and other software components must be accessible for users to integrate them optimally.

The two platforms look a lot alike, but there are many little and defining differences between Unix and Linux that cause problems if you're not aware of them.

Several Unix tools are noticeably absent on Linux servers. Unix admins use EMC's PowerPath to set up a redundant storage area network (SAN) connection to the servers, for example. On Linux, there is no PowerPath implementation available. High-performance file systems and volume managers, which you might have purchased with high license fees for your Unix servers, are missing on common Linux distributions. Does that make Linux an inferior platform? Chances are it's just different from what you expected.

The major difference between Linux and Unix is that everything on Linux is open source, and therefore available for free. Paying thousands of dollars for a tool on your older servers leaves a bitter taste in your mouth. Consider PowerPath for instance: All Linux distributions have a native tool -- the Device Mapper Multipath driver -- that is as good as PowerPath. Even EMC recommends you connect Linux servers to the SAN using the multipath driver.

On Linux servers, volume management eliminates purchasing expensive additional licenses to organize your storage in volumes. Linux comes with the Logical Volume Manager that includes everything to set up storage flexibly. Unix administrators typically don't have a problem working with these tools, but they also don't believe that a free and open source setup is as effective as the expensive proprietary solution.

In some cases, specific proprietary software modules are available for a Linux distribution. They typically come with the hardware you purchase. If that hardware is on your Linux distribution's hardware-support list, you won't have any problems. Your Linux vendor collaborates with the hardware vendor for optimal operation and support. Proprietary modules from hardware vendors often are supported only for enterprise Linux distributions including SUSE, Oracle, Ubuntu and Red Hat. Free distributions may not work well on this hardware.

Unix administrators typically monitor their IP configuration with the ifconfig command. On Linux, ifconfig exists as well, but has been deprecated since the release of the 2.0 kernel in 1996. Since then, the ip command is the only way to monitor everything that's happening on your servers. This versatile command has several options for managing network configuration.

Even if you're an experienced Unix administrator, consider migration training so that your skills transcend these differences between Unix and Linux.

About the author:
Sander van Vugt is an independent trainer and consultant based in the Netherlands. He is an expert in Linux high availability, virtualization and performance. He has authored many books on Linux topics, including
Beginning the Linux Command Line, Beginning Ubuntu LTS Server Administration and Pro Ubuntu Server Administration.

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