UNIX TO LINUX MIGRATION RICHARD KEECH ABSTRACT This paper aims to show the benefits of choosing Linux and migrating existing UNIX environments to the Linux platform. This applies in particular to migrations from RISC-based platforms. It also shows the extent to which Linux is now a trusted, mainstream platform and how any technical risks associated with migrations can be mitigated. This paper addresses a technical audience. www.redhat.com UNIX to Linux migration | Richard Keech TABLE OF CONTENTS AIMS Page 3 INTRODUCTION TO LINUX Page 3 OpEN SOURCE AND LINUX Page 4 RED HAT ENTErprISE LINUX Page 5 UNIX VS LINUX Page 8 TrENDS Page 9 Server Virtualization Page 9 Clustering Page 10 Rapid provisioning and appliance OS Page 10 Instrumentation and debugging Page 10 MIGRATION CONSIDERATIONS Page 11 Qualify the stack Page 11 Porting Page 12 Training Page 12 Prepare a Linux standard build Page 12 Pilot deployment Page 13 CONCLUSIONS Page 13 REFERENCES Page 14 2 www.redhat.com UNIX to Linux migration | Richard Keech AIMS This paper aims to give an introduction to Linux for the technically inclined and educated reader at a level that can allow proper comparisons with UNIX. The paper provides an outline of the key considerations in selecting Linux and migrating from UNIX to Red Hat Enterprise Linux. The intended audience of this paper is enterprise infrastructure architects. INTRODUCTION TO LINUX Benefits. The Linux platform offers a low-risk, robust, and value-for-money alternative to traditional UNIX. Linux is now sufficiently mature enough to handle the most demanding workloads at a much lower cost than proprietary UNIX offerings. At the same time, Linux leverages the open source development and subscription model, which guarantees a constant stream of innovation fueled by a healthy multi- dimensional community of users and developers. This is an important aspect, as not only does it truly prevent proprietary lock-in, but also enables a level of access to skills, documentation, on-line forums, and so on, to a level unheard of before with any other operating system.[20] Maturity. Large-scale commercial deployments of Linux became noticeable in 1998. With the benefit of another decade’s rapid development, Linux has reached a degree of maturity that meets or exceeds commercial UNIX. According to IDC,[1] “Linux ... early adoption patterns have given way to mainstream deployment.” Scalability. As an example of Linux’s capacity to scale up, in June 2008 the US Department of Energy announced the world’s fastest supercomputer known as Roadrunner[2] based on Red Hat Enterprise Linux.[3] Another recent example is the New York Stock Exchange Euronext (NYSE Euronext) runs its entire trading operations on Red Hat Enterprise Linux and replaced every popular flavor of UNIX to achieve the scalability and reliability they require. Feature-rich. Linux now more than holds its own for features compared to UNIX offerings. For some time Linux has included journaling file systems, logical volume management (LVM), advanced multipath IO capabilities, clustering, as well as services for modular provisioning, management, and patching. Today Linux comes standard with server virtualization and world-leading enhanced security such as SELinux. Solutions. There is a great breadth of solutions and software available on Linux today. Many customers have found that the bundled open source offerings, often referred to as the application stack, meets their needs. If not, then there is a large ecosystem of ISVs to choose from who now fully support Linux. This number continues to grow as more and more customers demand Linux support from their ISVs. www.redhat.com 3 UNIX to Linux migration | Richard Keech OPEN SOURCE AND LINUX The open source method. Organizations adopting Linux can be confident in the underlying open source method. According to the Open Source Initiative, “Open source is a development method for software that harnesses the power of distributed peer review and transparency of process. The promise of open source is better quality, higher reliability, more flexibility, lower cost, and an end to vendor lock-in.”[29] Open source maturity. Open source has emerged and matured to the point where it is now broadly accepted. Gartner has stated, “By 2012, more than 90 percent of enterprises will use open source in direct or embedded forms.”[4] Red Hat engineering. Linux distributors such as Red Hat start with the Linux kernel and many other pieces of open source software. Subsequent engineering processes create a coherent, tested, and enterprise-grade product. A key aspect of this process is creating a product life cycle and support services that match that of what businesses require. Specifically for Red Hat Enterprise Linux, this means turning a fast-moving, rapidly changing, innovating code base into something that has a life cycle spanning seven years. In a commercial setting the use of open source has been shown to be safe and free from licensing complications. Open standards. Open source development has a strong track record in following the most important open standards. Increasingly open source development is at the forefront of setting open standards, as has been seen with the emergence of the Open Doc (ODF) standards. Single vendor standards will never be Open Standards. That’s why open source is such a huge contributor to open standards: at the heart of each viable open source initiative or project is a thriving multi-vendor ecosystem. Accordingly, open source development generally has strong imperatives for interoperability. Access to source code. Openly available source code is a very important strategic factor that mitigates risk because it provides: • Verifiability. It is possible to verify that code does what it purports to do, and no more. This is relevant, for example, to confirm that a program does not have back doors or other unexpected ‘features.’ • Assurance of maintenance. Although Red Hat’s support and maintenance is first-class, access to source code means that an organization using Linux always has an alternative, independent of Red Hat. This is a kind of strategic insurance that proprietary software simply cannot provide. Not even through complicated escrow arrangements. • Local derivatives. Occasionally organizations might find that they need critical new features or capabilities in their software. Often such requirements can be met by working with Red Hat directly. However, access to code gives organizations the ultimate choice about how and when capabilities might be added to their software. 4 www.redhat.com UNIX to Linux migration | Richard Keech RED HAT ENTERPRISE LINUX Red Hat Enterprise Linux is the most successful commercially supported Linux distribution.[30] The current release is version 5, released in March 2007. Like its predecessors, Red Hat Enterprise Linux 5 entirely open source and offered commercially via a comprehensive annual support subscription. This subscription model is the basis for Red Hat’s successful and sustainable business model. Red Hat Enterprise Linux major releases, for example version 4 to version 5, occur about every two to two and a half years. Platforms. Red Hat Enterprise Linux is released on the industry’s broadest set of architectures: x86, x86_64, ia64, PowerPC (P- and I-Series), and (s390) Z-Series.[31] This breadth gives a wide range of migration options for organizations using multiple CPU architectures. Support. Red Hat supports Red Hat Enterprise Linux for seven years from the date of initial release.[5] Since Red Hat has no proprietary lock-in, quality support is paramount. One data point showing that Red Hat has been able to give high quality support is the CIO Insight Vendor Value study, which has ranked Red Hat number one enterprise software vendor for four years running.[6] Red Hat takes a highly conservative approach to issuing updates to Red Hat Enterprise Linux so as to reduce the risk of regressions and assure software compatibility[32] across minor releases.[9] Simply put, the stability that users of UNIX are accustomed to is made available for Linux through Red Hat Enterprise Linux. This has been a key enabler for enterprises around the world to reliably switch from proprietary UNIX to Red Hat Enterprise Linux. Capabilities and features. The core technical capabilities of Red Hat Enterprise Linux are available for review at www.redhat.com/rhel/compare/. The table shown here summarizes some of the key supported extremes for a single node running on the commonly used Intel X86_64 architecture using Red Hat Enterprise Linux 5. ITEM VALUE Max RAM 512 GB Max physical/logical CPUs 64/255 Max filesystem sizes 16 TB Max file size 2 TB Software packaging. Red Hat uses a modular software packaging technology called RPM.[12] All Red Hat software is issued as RPM packages, regardless of whether it is core operating system or add on software. The use of RPM underlies Red Hat’s ability to install and manage software efficiently. The RPM standard has been adopted by nearly all commercial Linux vendors. www.redhat.com 5 UNIX to Linux migration | Richard Keech ISVs. Increasingly organizations considering Linux migrations will find that their current software stack is already supported on Red Hat Enterprise Linux. Some compatible software can be seen at www.redhat.com/rhel/compatibility/software/. In many cases, support for Red Hat Enterprise Linux is long-standing. For example, in 1998 all the major commercial database vendors announced support within in the space of a few months.[7] Best practice software packaging by ISVs is to use RPM packages. Variants. Red Hat Enterprise Linux 5 is available in a number of variants. Red Hat Enterprise Linux Server and Red Hat Enterprise Linux Advanced Platform are the server variants. There is also Red Hat Enterprise Linux 5 Desktop. Advanced Platform offers clustering as well as support for unlimited number of virtual machine instances through the integrated virtualization (see Server Virtualization, below).