Consider using POSIX-compliant distributions, like Red Hat and SUSE, to ease migration from POSIX-compliant Unix versions such as AIX, HP-UX and Solaris, says Michael Palmer. Palmer, the co-author of Guide to UNIX Using Linux, Third Edition (Course Technology), states that Red Hat and SUSE can be simpler to use because of their strong support.
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Get comprehensive, step-by-step advice for your Unix-to-Linux migration testing environment and hardware optimization tips in this interview.
Which distribution has the easiest Unix-to-Linux migration path, and why? How much does distribution choice count when making a migration?
Michael Palmer: In general, it is easiest to move from POSIX-compliant versions of Unix to Linux, which is POSIX-compliant. For example, IBM AIX, HP-UX and Solaris are POSIX-compliant, commercial versions of Unix. Red Hat Enterprise Linux (RHEL) and SUSE Linux use a standard Linux kernel that is POSIX-compliant.
Migrating to RHEL or SUSE Linux also can be easier, because these distributions have a large client base with strong support from Red Hat, Novell and IBM. For instance, Novell and IBM offer the Migration Kit for Solaris OS to Linux.
It is important to recognize that problems will arise in any migration. By selecting Red Hat Enterprise Linux or SUSE Linux, there are likely to be people who have already solved the particular problems an organization encounters.
Does hardware optimization differ much for Unix vs. Linux? Would shops need to upgrade hardware in conjunction with a migration?
Palmer: Hardware optimization depends on several factors. One factor is the use of X Window and a desktop. Another is the use of GUI open source software.
Consider a legacy Unix system that is configured to run entirely from the command line. The legacy system might run very comfortably on a slower processor, such as a Pentium II computer. In a migration to Linux, the user may decide to implement X Window, GNOME and open source programs such as the OpenOffice.org office suite.
In this context, a hardware upgrade is needed. The new configuration requires a fast processor and more memory. It might be possible to run on the old machine, but the response would be painfully slow.
Linux distributions evolve into new releases as often as two or more times a year. Each new release incorporates more features to take advantage of new hardware and software options.
In some situations, each new release comes with more software, more utilities and the latest version of a desktop, such as GNOME or KDE. Distribution CDs have grown from one CD to multiple CDs. For these reasons, an older computer may not have a fast enough processor, enough RAM or disk storage -- or a combination of these.
What are some guidelines for migrating to Linux from Unix?
Palmer: A migration involves tasks that are similar to performing a major operating system upgrade. Migration guidelines include:
- Begin by assembling a migration team of systems programmers, application programmers, users from affected areas, appropriate managers and a project manager.
- Use the team to establish project management tasks and to assign the tasks to specific individuals.
- Obtain migration tools for the operating system, software, databases and utilities.
- Create a migration test environment -- that is not live -- on one or more systems, like servers and workstations.
- Install the new operating system and test it. Install updates and patches and test them.
- Test network connectivity and response.
- Port key application software packages one-by-one, and test each one.
- Install all software patches and updates and test them.
- Port databases one by one, install patches and updates and test them using known test data.
- Involve a sampling of users to test the software and systems they use.
- Set up user training, if needed, for any changes or new software.
- Create and test backups of the Unix system(s) before migrating. Have both on-site and off-site backups for a fail-safe backup strategy.
- Migrate and test one system at a time, such as an accounting server, a database server, an inventory server and so on. Never migrate all systems at once.
- Establish a cutover date from the test environment to a live environment.
- For mission-critical systems, run both the old and new systems for a designated period until it is certain that all problems are detected and resolved on the new systems.
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