The Evolution of SUSE Linux Enterprise Server, 25 years of Enterprise Linux

Since the launch in 2000 of the first SUSE Linux Enterprise Server (SLES), or as we referred to it then: “SuSE Linux Enterprise Server for S/390”,  it has been the cornerstone of business critical enterprise-grade Linux distributions. Its reputation for stability, security, performance, and innovation has been well earned. Over the years, SLES has seen significant changes with each major version, reflecting advancements in technology and shifting industry needs. Let’s take a look at the evolution of SLES in the past 16 years, from origin to version 11, launched in 2009, through 12, 15, and a glimpse into the path toward SLES 16.

SUSE Linux Enterprise – Press release year 2000

SUSE Linux Enterprise Server: The origin of an Enterprise Linux

Release Date: October 2000
As the 21st century began, Linux was increasingly adopted for diverse workloads. Enterprises recognized the need for a stable, secure, performant, and innovative enterprise-grade Linux distribution capable of running critical business applications, including those alongside existing mainframe systems. SUSE Linux Enterprise Server was designed to address that challenge, pioneering a reliable foundation for business-critical applications requiring a robust Linux operating system. SUSE Linux Enterprise Server (SLES) was first released in 2000. Specifically, we initially released it for IBM S/390 mainframes in October 2000, followed by (32bit) x86 versions in April 2001.

Let’s skip versions 7, 8, and 9, and continue with version 11 …

SUSE Linux Enterprise Server 11: Foundation of Enterprise Reliability

Release Date: March 24, 2009

Based on the foundations of SLES 9 (August 2004) and 10 (July 2006) SUSE Linux Enterprise Server 11 was launched. Built on SUSE’s reputation for delivering robust Linux systems, focusing on high availability, virtualization, and simplified management. This version included:

• Kernel: Based on Linux kernel 2.6.27, updated to 2.6.32 in Service Pack 1 (SP1),  and finally to 3.0 for SP2 and later, offering better hardware support and performance improvements. 
• Openssl: Version 0.9.8, providing robust cryptographic capabilities.
• SysV init: SLES 11 continued using the traditional init system with tools like “chkconfig” or “service” to simplify its management 
• SSH: OpenSSH 5.1 initially updated to 6.6 in SP4 ensuring secure remote access and enabling the new privilege separation sandbox.

User Experience

In SUSE Linux Enterprise Server 11 the YaST (Yet another Setup Tool) which doubled as installer and system management tool,  included enhancements for partitioning and software selection. It relied on ZYpp (Zen / YaST Packages Patches Patterns Products), and the “zypper” cli tool for software management, making it very easy for sysadmins to keep their systems up to date.

SLES 11 also introduced AppArmor for application security and had a strong focus on virtualization with integrated support for Xen and KVM.

SUSE Linux Enterprise Server 12: Transition and Modernization

Release Date: October 27, 2014

SLES 12 marked a significant shift with its embrace of modern technologies, aligning with contemporary Linux standards:

• Kernel: With SUSE Linux Enterprise 12 we introduced the “Tik-Tok” model for kernel updates within major releases. This unique new ‘Tik-Tok’  model for the Linux kernel and other core components allowed SLES to innovate faster during its long lifecycle – by keeping full ABI compatibility for applications. Starting with Linux kernel 3.12 (SP0/SP1), delivering better scalability and performance. Followed by 4.4 (SP2/SP3) and finally updated to 4.12 (SP4/SP5). The latter shared the code base with SUSE Linux Enterprise 15 SP0 for support of NVDIMM.
• OpenSSL: Version 1.0.1, featuring support for TLS 1.2.
• Systemd: Introduced as the default init system, replacing SysV init, leading to faster boot times and improved process management.
• SSH: OpenSSH 6.6, with enhancements for stronger encryption algorithms. Updated to 8.4 in SP5 

User Experience

A redesigned YaST installer with a graphical interface built using Ruby, enhancing usability and simplifying tasks for system administrators. Continued use of Zypper and RPMs, with improved dependency resolution, making the installation and update of software a breeze.

SLES 12 also introduced features like full system rollback with Btrfs, a copy on write filesystem, as the default filesystem and live kernel patching, minimizing downtime for critical systems. The “snapper” tool made it super simple to manage the snapshots. As they are filesystem based, they work on any platform making it possible to even show differences between files from various snapshots.

The inclusion of Docker in Service Pack 1 (SP1) and the release of minimized JeOS (Just Enough Operating System) images, established the initial steps to support containerized workloads on the operating system.

SUSE Linux Enterprise Server 15 and openSUSE Leap 15: The Hybrid Present

Release Date: July 16, 2018

With SLES 15, SUSE aimed to bridge traditional and software-defined infrastructure, emphasizing containerization and cloud-native workloads:

• Kernel: Linux kernel 4.12 (SP0/SP1; codebase shared with SLE 12 SP4, but different configuration), optimized for container performance and hardware advancements. Updated to 5.3 (SP2/SP3), 5.14 (SP4/SP5), and finally 6.4 for Service Pack 6 and 7 (SP6/SP7).
• OpenSSL: Version 1.1, version 3.x was added in SP4, and version 3.1.4 became default in SP6 to build for the long life cycle of SUSE Linux Enterprise 15 , supporting modern cryptographic standards.
• Systemd: Continued as the standard init system, benefiting from upstream enhancements.
• SSH: OpenSSH 7.6, incorporating security updates and new features like elliptic curve cryptography. Updated to 9.6 in SP6.
• Base Container Images BCI: A set of images, derived from SLES 15, that can be used to build your own images with confidence that every component has full traceability. Comes in different flavors: 
  • Micro: fully minimized
  • Minimal: minimized but with usual tools
  • Init: Includes systemd, to begin containerization journey of traditional apps
  • FIPS:-140-3: For containers that require this certification

User Experience

The YaST installer gained new workflows for hybrid deployments, including support for transactional updates. The adoption of widespread system tools like “cockpit” was started to facilitate the work for system administrators coming from other Linux flavours.

Unified package repositories for SLES and openSUSE Leap simplified transitions between platforms, closing the “Leap gap”. This means that a project can be started with openSUSE Leap 15 and then, in a supported manner, convert the system to SUSE Linux Enterprise 15 to receive support, certifications, professional services and all the value coming from SUSE.

SUSE Linux Enterprise Server 15 introduced a modular approach, decoupling the core OS from application modules to allow faster updates and innovations. It also emphasized container technologies, integrating tools like Docker and Podman. 

A new version of the minimized OS, with orientation towards transactionality and immutability was created and released as SLE Micro 5 (SLES number minus 10) to better support containerized workloads.

Tools like SUSE Manager / Uyuni and Trento started providing containerized versions to run on SLE Micro releases.

OpenSUSE Tumbleweed

A very different breed of distribution merging all the beauty from numbered releases but with a rolling release mechanism makes it the flagship of the openSUSE project. 

The development model consists of making the build of the linux releases as open and automated as possible. This is supported by the Open Build Service, which has even been adopted by Kubernetes to generate its official builds. That handles automated generation  of packages for multiple Linux distributions for a broad range of hardware architectures (x86, arm64, s390x, ppc64l). Coupling this with a fully open Quality Assurance (QA) system, called openQA, makes it not just possible, but easy, to release a full distribution almost on a daily basis. 

Toward SUSE Linux 16: The Next Frontier

While SUSE Linux Enterprise Server 16 has not yet been officially released, insights from openSUSE Leap 16 provide a glimpse of its potential direction of SUSE Linux 16. The development process is based on a common code shared among all new SUSE Linux versions. Starting from SUSE Linux Micro 6.X involving SUSE Linux 16 and going beyond to new Cloud Native related projects (stay tuned for more info on this). We refer to this new way to create SUSE Linux as SUSE Linux Framework One. The base of this new generation of Linux includes:

• Codebase:  New common shared codebase for all SUSE Linux products.
• Kernel: Expected adoption of a 6.4 or newer kernel, with enhanced security and performance features.
• Systemd: Continued evolution with better integration for cloud and container environments.
• SSH: Version 9.9 with focus on quantum-safe cryptography to address emerging threats.

Strategic changes

In SUSE Linux 16 the strategic approach will focus on three points: Predictable Cadence, Framework One and Mainstream Technologies.

Predictable cadence: In SUSE Linux 16 we will be converging all Linux branches to make them more predictable and completely aligned to the release cycles of other products in the company. The plan is to have a yearly release by November of SUSE Linux and all derivatives in a constant predicable cadence. The lifecycle of the core packages will be also aligned, not only to the current use cases (i.e. SAP, LoB apps, Infra services, etc) but also to the extended workloads running on top of it (Kubernetes via RKE2 and K3S, Edge and AI). This way SUSE Linux will better integrate and support all kinds of workloads making it easy for users and customers to build a sensible plan around it knowing that we will be backing them.

Framework One: As a result, a new unified workflow, including a new approach to software lifecycle management and delivery, is required to support SUSE Linux 16. Not only it but also its multiple derivatives and use cases keeping the coherence that enterprise linux must have. With SUSE Linux Micro 6.X, and now with SUSE Linux 16, we merge all branches into a unified structure and methodology to build Linux. This ‘Framework One’ is our new way of building SUSE Linux, with all subsequent options becoming products of this framework. For example, this “Framework One” allows that, from SUSE Linux 16.1 onwards, SUSE Linux Micro innovation will be merged and delivered as part of an immutable/transactional mode on SUSE Linux Enterprise Server 16. This provides a flexible common foundation easier to support and certify. As a consequence it leads to a wider number of certifications and more efficient processes. We will also approach each set of packages providing a capability with a time span that makes sense for users and customers. This is one of the beauties of SUSE Linux Framework One, the possibility to keep an innovative Linux having different versions of different packages available, enabling the core OS to have the longest support lifecycle.

Mainstream Technologies: SUSE is dedicated to providing a long-lasting, futureproof enterprise Linux platform. We strategically adopt mainstream and innovative open-source technologies, replacing long-standing projects with futureproof alternatives to ensure SUSE Linux remains relevant and valuable in the long term. Our approach honors the trust of our existing SUSE Linux Enterprise Server customers providing a better Linux, while the incorporation of mainstream technologies also makes SUSE Linux 16 a welcoming destination for new users smoothing their transition from other distributions. Alongside well-established tools like SELinux, Cockpit, and Ansible System Roles, we are incorporating and enhancing futureproof innovations like Agama and BTRFS with Snapper. This ensures that all Linux users find SUSE Linux 16 a comfortable, powerful, and reliable environment built for the long haul.

SUSE Linux Enterprise Server 16 is poised to build on SUSE’s heritage, catering to the current hybrid IT world that spans on-premises, cloud, and edge computing environments. All this while we are prepared for future requirements with the legendary reliability that made it the favorite Linux for business critical workloads.

User Experience

After a long development process, Agama, a service-based installer is available to deploy new systems, making it the new default installer for all new projects which will be based on SUSE Framework One.

Until SLES 15 the runtime support for 32 bits was kept, which limited the lifecycle to 2037 to avoid the Year 2038 problem, which is the end of (long term) support for the Service Pack 7 of this version. With SLES 16 only 64 bits architectures will be supported. This means that the engineering process that we have to build it and maintain SUSE Linux doesn’t have a predefined limit for its lifecycle. We also leverage the principle that we maintain ABI compatibility across major releases, even when we use the Service Pack mechanism to update main package versions.

Conclusion

The journey from the initial releases of SUSE Linux Enterprise Server to the anticipated SUSE Linux 16 reflects a continuous commitment to open source, delivering enterprise-grade solutions that evolve with technological advancements. Each version has introduced groundbreaking features, from the adoption BTRFS in SLES 11 and Systemd in SLES 12 via the modular and more container oriented design in SLES 15 to the dynamic lifecycle design in SUSE Linux Enterprise Server 16. As the new release looms on the horizon, it’s clear that at SUSE we are well-prepared to address the challenges of the modern IT landscape, leveraging insights from openSUSE to shape its future.

Try it yourself. https://www.suse.com/download/sles/ 

Note: This article wouldn’t have been possible without the help of Matthias Eckermann and Sebastian Martínez.