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Archive date: 2022-05-31

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It's been 20 years since IBM first released Linux on IBM Z, so I thought it appropriate to mark the occasion by exploring the history, the details, and the large ecosystem of open source software that's now available for the IBM Z and LinuxONE platforms.

IBM has deep roots in the open source community. We have been backing emerging communities from a very early stage -- including the Linux Foundation, the Apache Software Foundation, and the Eclipse Foundation. This includes years of contributions to the development of open source code, licenses, advocating for open governance, and open standards in addition to being an active contributor to many projects.

As open source continues to gain momentum in the software world, we see growth reflected across different hardware and processor architectures. The processor architecture for IBM Z and LinuxONE is known as s390x.

If you're new to these two hardware platforms, they are commonly known as mainframes. IBM Z has had a tremendous evolution with world-class, enterprise-grade features for performance, security, reliability, and scale. The latest version, IBM z15, can co-locate different operating systems including Linux, z/OS, z/VSE, and z/TPF. The LinuxONE III model has the same features as IBM Z, but was designed exclusively for the Linux operating system, including most commercial and open source Linux distributions.

When we talk about commonalities, there’s one that is not very well known related to mainframes -- open source software. Did you know that open source software (OSS) for mainframes existed as far back as 1955? SHARE, a volunteer-run user group, was founded in 1955 to share technical information related to mainframe software. They created an open SHARE library with available source code, and undertook distributed development. It was not called "open source" back then, but we can consider that one of the early origins of open source.

Open source software, Linux, and IBM

The popularity of open source software originated in large part as a result of years of cultural evolution through sharing libraries across all programming languages. Innovating and sharing software with reusable functionality has become a common practice led by open source communities and some of the largest organizations in the world. Another factor is that all of the latest technologies are being developed in the open -- AI, machine learning, blockchain, virtual reality, and autonomous cars, just to name a few.

As mentioned earlier, open source is not new to mainframes -- another example is Linux, which has been used for more than 20 years. In 1999, IBM published a collection of patches and additions to the Linux kernel to facilitate the use of Linux in IBM Z. Then, in 2000, more features were added to the mainframes, including the Integrated Facility for Linux (IFL), which hosts Linux with or without hypervisors for virtual machines (VMs).

Over the last 20+ years, IBM has committed significant resources to Linux. In 2000, IBM announced a $1 billion investment to make Linux a key part of the company strategy, establishing IBM as a champion for contributions to the Linux kernel and subsystems.

One of IBM's key contributions to Linux has always been enhancements that take advantage of the unique capabilities of the mainframe. Today, IBM Z and LinuxONE run a much-improved open source Linux that allows amazing technology for high I/O transactions, cryptographic capabilities, scalability, reliability, compression, and performance.

All commercial and open source Linux distributions are available for IBM Z and LinuxONE: Red Hat Enterprise Linux, SUSE Linux Enterprise Server, Ubuntu, Fedora, Debian, Open SUSE, CentOS, Alpine, and ClefOS.

The use of Linux over the course of 20 years has opened the doors to a vast ecosystem of open source software for IBM Z and LinuxONE.

The open source software ecosystem for S390x

Today, in line with its commitment to Linux, IBM contributes to many open source projects. In fact, together with Red Hat, which is now part of IBM, it has the largest number of active open source contributors in the world -- an amazing feat.

Because IBM is committed to the goal of continuing to develop the open source software ecosystem for IBM Z and LinuxONE, the company has teams of full-time developers that contribute upstream back to open source communities. In general terms, all you need is a different compiled Linux distribution for s390x; then, if you want to port exiting software, you will have to build or compile it again on IBM Z or LinuxONE.

Open source communities and IBM upstream developers address technical items specific to s390x, especially when related to existing open source software for x86 processors that need to be ported and validated on an IBM Z or LinuxONE (s390x).

Technical considerations for porting OSS to S390x

First, it's important to note that most software recompiles or builds with minimal to no changes; x86-specific components will cause compilation or runtime errors. In those cases, code needs to be added to make those libraries or components work for s390x.

S390x uses big-endian memory allocation. The big-endian scheme stores the most significant byte (MSB) first, while the little-endian scheme available in ARM and x86 processors stores the least-significant byte (LSB) first. What this means is that if the software is doing low-level memory allocation in a little-endian scheme, the code needs to be adjusted to big-endian so the application can continue to work properly in the mainframe.

The same considerations apply to library dependencies (transitive libraries) in which functionality specific to other processor architectures needs to change to work on s390x.

Every tool, script, and piece of software is different, but for the most part, the previous technical considerations apply, and in many cases, no code changes are required -- all you have to do is build or compile the software again.

Growing the open source ecosystem

There you have it! Coding and building OSS are basically the same on any platform. The use of Linux and re-use of open source technologies, together with commonly used open source development tools and languages, have helped to grow the ecosystem of OSS for IBM Z and LinuxONE. We have seen more interest in recent months, and we are looking forward to having more OSS (especially in the AI space) being available for s390x.

Open source on IBM z/OS is a topic for another blog post, but it too is seeing growth including Linux Foundation projects like Zowe.

Open source ecosystem - logos

We invite you to participate. We have a growing community, and there are resources available for you to try in the IBM LinuxONE Community Cloud. Developers and enterprises are sure to enjoy the benefits of working in a familiar open source environment.

Finally, please check out my recent IBM Z Day talk, "20 years of open source software growth for Linux on IBM Z, and more to come!" I covered these open source ecosystem topics and then answered live questions. You can find this and all of the conference replays on the IBM Z Day site.

Twenty years of open source software for IBM Z and LinuxONE

Twenty years of open source software for IBM Z and LinuxONE