On the digital transformation journey to a full cloud-native landscape, the use of microservices becomes the main approach with the dominant technology for such container orchestration being Kubernetes.⁠^[1] With its large community of developers and abundant features and capabilities, Kubernetes has become the de-facto standard and is included across most container-as-a-service platforms. With all of these technologies in place, both developer and operation teams can effectively deploy, manage and deliver functionality to their end users in a resilient and agile manner.

Agility is driving developers toward more cloud-native methodologies that focus on microservices architectures and streamlined workflows. Container technologies, like Kubernetes, embody this agile approach and help enable cloud-native transformation.

By unifying IT operations with Kubernetes, organizations realize key benefits like increased reliability, improved security and greater efficiencies with standardized automation. Therefore, Kubernetes infrastructure platforms are adopted by enterprises to deliver:

2.2 Business value #

 

After two years of research and development in June 2020, K3s was donated to the CNCF. The donation is a testament of the commitment to the open source community and their mission to run Kubernetes everywhere.

Perfect for Edge

K3s is a highly available, certified Kubernetes distribution specifically designed for production workloads in unattended, resource-constrained, remote locations or inside IoT appliances.

Simplified & Secure

K3s is packaged as a tiny, single binary that reduces the dependencies and steps needed to install, run and auto-update a production Kubernetes cluster. For workloads, automated Manifest and Helm Chart managment deployments can be used. Also, multiple architectures, like x86_64, ARM64, and ARMv7, are supported with binaries and images available.

Given its extensive Kubernetes capabilities, K3s can also be a suitable choice for:

• embedded platforms,

• continuous integration and continuous deployment platforms,

• branch locations or individual developer deployments, and

• even core or cloud production instances

Tip

When K3s is imported and combined with SUSE Rancher, organizations are equipped with an easy, complete and reliable management solution for Kubernetes at the edge.

With this increased consistency of the deployed and managed Kubernetes infrastructure clusters, organizations benefit from an even higher level of the Cloud Native Computing model where each layer only relies upon the API and version of the adjacent layer, such as:

Compute Platform

Using the above software application and technology solutions with the server platforms offered by Dell Technologies provides many alternative for scale, cost-effectiveness and performance options that could align with local IT staff platform preferences:

• density-optimized - high performance and efficiency for big data and the most demanding workloads

• mission-critical - systems of intelligence to fuel your digital transformation in a world where time and data are the new currency and business continuity is expected

• composable - fully adaptable and ready for Hybrid-IT to future-proof your data center for today’s workloads and tomorrow’s disruptors

• IoT - realize the potential of the Internet of Things to provide compute at the network edge

• cloud - high-capacity, mass-compute open infrastructure with security and software to match

• and virtualized use cases.

This section outlines the core elements of the K3s solution, along with the suggested target platforms and components.

3.1 Solution architecture #

 

The figure below illustrates the high-level architecture of K3s:

Figure 3.1: Architecture Overview - K3s #

 

Container Runtime

• Containerd & runc

• Kine as a datastore shim that allows etcd to be replaced with other databases

Networking

• Flannel for CNI

• Kube-router for network policy

Services

• CoreDNS

• Metrics Server

• Traefik for ingress

• Klipper-lb as an embedded service load balancer provider

• Local-path-provisioner for provisioning volumes using local storage

Workloads

Helm-controller to allow for CRD-driven deployment of helm manifests

Host utilities

iptables/nftables, ebtables, ethtool, and socat

When this is set up, users can interact with K3s via

• kubectl

  • directly on the K3s host or

  • remotely, leveraging the KUBECONFIG file of the K3s cluster’s deployment (/etc/rancher/k3s/k3s.yaml)

• manual or automatic, manifest or Helm Chart based, workload deployments

This section describes the various components being used to create a K3s solution deployment, in the perspective of top to bottom ordering. When completed, the K3s instance can be used as the application infrastructure for cloud-native workloads and can be imported into SUSE Rancher for management.

4.2 Software - K3s #

 

K3s is packaged as a single binary, which is about 50 megabytes in size. Bundled in that single binary is everything needed to run Kubernetes anywhere, including low-powered IoT and Edge-based devices. The binary includes:

• the container runtime

• important host utilities such as iptables, socat and du

The only OS dependencies are the Linux kernel itself and a proper dev, proc and sysfs mounts (this is done automatically on all modern Linux distributions). K3s bundles the Kubernetes components:

• kube-apiserver,

• kube-controller-manager,

• kube-scheduler,

• kubelet and

• kube-proxy

into combined processes that are presented as a simple server and agent model, as represented in the following figure:

Figure 4.1: Component Overview - K3s #

 

K3s can run as a complete cluster on a single node or can be expanded into a multi-node cluster. Besides the core Kubernetes components, these are also included:

• containerd,

• Flannel,

• CoreDNS,

• ingress controller and

• a simple host port-based service load balancer.

All of these components are optional and can be swapped out for your implementation of choice. With these included components, you get a fully functional and CNCF-conformant cluster so you can start running apps right away. K3s is now a CNCF Sandbox project, being the first Kubernetes distribution ever to be adopted into sandbox.

Tip

Learn more information about K3s

As K3s can be deployed on a single or multiple nodes, the next sections describe the suggested component layering approach.

4.4 Compute Platform #

 

Leveraging the enterprise grade functionality of the operating system mentioned in the previous section, many compute platforms can be the foundation of the deployment:

• Virtual machines on supported hypervisors or hosted on cloud service providers

• Physical, baremetal or single-board computers, either on-premises or hosted by cloud service providers

Note

To complete self-testing of hardware with SUSE YES Certified Process, you can download and install the respective SUSE operating system support-pack version of SUSE Linux Enterprise Server and the YES test suite. Then run the tests per the instructions in the test kit, fixing any problems encountered and when corrected, re-run all tests to obtain clean test results. Submit the test results into the SUSE Bulletin System (SBS) for audit, review and validation.

Tip

Certified systems and hypervisors can be verified via SUSE YES Certified Bulletins and then can be leveraged as supported nodes for this deployment, as long as the certification refers to the respective version of the underlying SUSE operating system required.

Dell EMC PowerEdge Rack Servers help you build a modern infrastructure that minimizes IT challenges and drives business success. Choose from a complete portfolio of 1, 2, and 4-socket rack servers to deliver high core density for your traditional applications, virtualization, and cloud-native workloads. Enhanced memory speeds, faster NVMe storage options, and BIOS tuning allows you to match performance to your workload for ultimate efficiency

4.4.1 Dell EMC PowerEdge R640 Rack Servers #

 

Note

The EMC PowerEdge R640 is SUSE YES Certified Hardware.

Uncompromising performance and density

The Dell EMC PowerEdge R640 is the ideal dual-socket, 1U platform for dense scale-out data center computing. The R640 combines density, performance and scalability to optimize application performance and data center density

• CPU : Up to two 2nd Generation Intel Xeon Scalable processors with up to 28 cores per processor

• Accelerators : Up to one single-width FPGA, Up to three single-width GPU (NVIDIA T4)

• Memory

  • Speed : DIMM Speed (Up to 2933MT/s)

  • Type : RDIMM, LRDIMM, NVDIMM, DCPMM (Intel Optane) DC persistent memory)

  • Module Slots : 24 DDR4 DIMM slots (12 NVDIMM or 12 DCPMM only) Supports registered ECC DDR4 DIMMs only

  • RAM : RDIMM 1.53TB, LRDIMM 3TB, NVDIMM 192GB, DCPMM 6.14TB (7.68TB with LRDIMM)

• Storage

  • Front Bays : Up to 10 x 2.5” with up to 8 NVMe, SAS/SATA/SSD/NVMe, max 76.8TB

    • Up to 10 NVMe, max 64TB

    • Up to 4 x 3.5” SAS/SATA, max 56T

  • Rear Bays : Up to 2 x 2.5” SAS/SATA/SSD/NVMe, max 15.36TB

Tip

For more information, see Dell EMC PowerEdge R640 Datasheet

Maximize application performance and density

The scalable business architecture of the R640 is designed to maximize application performance and provide the flexibility to optimize configurations based on the application and use case. With the R640 you can create an NVMe cache pool and use either 2.5” or 3.5” drives for data storage. Combined with up to 24 DIMM’s, 12 of which can be DCPMMs or NVDIMMs, you have the resources to maximize application performance with the optimum configuration in only a 1U chassis.

• Simplify deployments and speed deployments with Dell EMC ready nodes for ScaleIO and VSAN.

• Maximize storage performance with up to 10 NVMe drives or 12 2.5” drives.

• Scale compute resources with 2nd Generation Intel Xeon Scalable processors and tailor performance based on your unique workload requirements.

Automate maintenance with Dell EMC OpenManage

The Dell EMC OpenManage portfolio helps deliver peak efficiency for EMC PowerEdge servers, delivering intelligent, automated management of routine tasks. Combined with unique agent-free management capabilities, the R640 is simply managed, freeing up time for high profile projects.

• Simplify management with the OpenManage Enterprise console, with customized reporting and automatic discovery.

• Take advantage of QuickSync 2 capabilities and gain access to your servers easily through your phone or tablet.

Guard your data center with built in security

Every EMC PowerEdge server is designed as part of a cyber resilient architecture, integrating security into the full server life cycle. The R640 leverages new security features built-into every new EMC PowerEdge server strengthening protection so you can reliably and securely deliver accurate data to your customers no matter where they are. By considering each aspect of system security, from design to retirement, Dell EMC ensures trust and delivers a worry-free, secure infrastructure without compromise.

• Rely on a secure component supply chain to ensure protection from factory to the data center.

• Maintain data safety with cryptographically signed firmware packages and Secure Boot.

• Prevent unauthorized or malicious change with Server Lockdown.

• Wipe all data from storage media including hard drives, SSDs and system memory quickly and securely with System Erase.

4.4.2 Dell EMC PowerEdge R740 Rack Servers #

 

Note

The EMC PowerEdge R740 is SUSE YES Certified Hardware.

Optimized for workload acceleration

The Dell EMC PowerEdge R740 is designed to accelerate application performance leveraging accelerator card and storage scalability. The 2-socket, 2U platform has the optimum balance of resources to power the most demanding environments

• CPU : Up to two 2nd Generation Intel Xeon Scalable processors with up to 28 cores per processor

• Accelerator : Up to three 300W or six 150W GPUs, Up to three double-width or four single-width FPGAs

• Memory

  • Type : RDIMM, LRDIMM, NVDIMM, DCPMM (Intel Optane DC persistent memory)

  • Module Slots : 24 DDR4 DIMM slots (12 NVDIMM or 12 DCPMM only), Supports registered ECC DDR4 DIMMs only

  • RAM : RDIMM 1.53TB, LRDIMM 3TB, NVDIMM 192GB, DCPMM 6.14TB (7.68TB with LRDIMM)

• Storage : Front Bays: Up to 16 x 2.5” SAS/SATA/SSD, max 122.88TB, Up to 8 x 3.5” SAS/SATA, max 128TB

Tip

For more information, see Dell EMC PowerEdge R740 Rack Servers

Expand and optimize application performance

The scalable business architecture of the R740 can scale up to three 300W or six 150W GPUs, or up to three double-width or four single-width FPGAs. With up to 16 2.5” drives or 8 3.5” drives the R740 provides the versatility to adapt to virtually any application and provides the perfect platform for VDI deployments.

• Scale your VDI deployments with 3 double-width GPUs, supporting up to 50% more users when compared to R730.

• Free up storage space using internal M.2 SSDs optimized for boot.

• Scale compute resources with 2nd Generation Intel Xeon Scalable processors and tailor performance based on your unique workload requirements.

Automate systems management with OpenManage

The Dell EMC OpenManage portfolio helps deliver peak efficiency for EMC PowerEdge servers, delivering intelligent, automated management of routine tasks. Combined with unique agent-free management capabilities, the R740 is simply managed, freeing up time for high profile projects.

• Simplify management with the New OpenManage Enterprise console, with customized reporting and automatic discovery.

• Take advantage of QuickSync 2 capabilities and gain access to your servers easily through your phone or tablet.

Rely on EMC PowerEdge with built-in security

Every EMC PowerEdge server is designed as part of a cyber resilient architecture, integrating security into the full server lifecycle. The R740 leverages new security features built-into every new EMC PowerEdge server strengthening protection so you can reliably and securely deliver accurate data to your customers no matter where they are. By considering each aspect of system security, from design to retirement, Dell EMC ensures trust and delivers a worry-free, secure infrastructure without compromise.

• Rely on a secure component supply chain to ensure protection from factory to the data center.

• Maintain data safety with cryptographically signed firmware packages and Secure Boot.

• Prevent unauthorized or malicious change with Server Lockdown.

• Wipe all data from storage media including hard drives, SSDs and system memory quickly and securely with System Erase

4.4.3 Dell EMC PowerEdge R650 Rack Servers #

 

Note

The EMC PowerEdge R650 is SUSE YES Certified Hardware.

Compelling performance, high scalability, and density

The Dell EMC PowerEdge R650 is a full-featured enterprise server, designed to optimize workloads performance and data center density

• CPU : Up to two 3rd Generation Intel Xeon Scalable processors, with up to 40 cores per processor

• Memory : 32 DDR4 DIMM slots, supports RDIMM 2 TB max or LRDIMM 4 TB max, speeds up to 3200 MT/s, Up to 16 Intel Persistent Memory 200 series (BPS) slots, 8 TB max, Supports registered ECC DDR4 DIMMs only

• Storage Controllers

  • Internal controllers: PERC H745, HBA355I, S150, H345, H755, H755N

  • Boot Optimized Storage Subsystem (BOSS-S2): HW RAID 2 x M.2 SSDs 240 GB or 480 GB

  • External PERC (RAID): PERC H840, HBA355E

• Drive Bays

  • Front bays : Up to 10 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 153 TB, Up to 4 x 3.5-inch SAS/SATA (HDD/SSD) max 64 TB, Up to 8 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 122.8 TB

  • Rear bays : Up to 2 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 30.7 TB

Tip

For more information, see Dell EMC PowerEdge R650 Datasheet

Innovate at scale with challenging and emerging workloads

The Dell EMC PowerEdge R650, powered by the 3rd Generation Intel Xeon Scalable processors is the optimal rack server to address application performance and acceleration. The EMC PowerEdge R650, is a dual-socket/1U rack server that delivers outstanding performance for the most demanding workloads. It supports 8 channels of memory per CPU, and up to 32 DDR4 DIMMs @ 3200 MT/s speeds. In addition, to address substantial throughput improvements the EMC PowerEdge R650 supports PCIe Gen 4 and up to 10 NVMe drives with improved air-cooling features and optional Direct Liquid Cooling to support increasing power and thermal requirements. This makes the EMC PowerEdge R650 an ideal server for data center standardization on a wide range of workloads including; Database and Analytics, HighFrequency Trading, Traditional corporate IT, Virtual Desktop Infrastructure, and even HPC or AI/ML environments that require performance, and GPU support in a dense 1U form factor

Increase efficiency and accelerate operations with autonomous collaboration

The Dell EMC OpenManage systems management portfolio tames the complexity of managing and securing IT infrastructure. Using Dell Technologies’ intuitive end-to-end tools, IT can deliver a secure, integrated experience by reducing process and information silos in order to focus on growing the business. The Dell EMC OpenManage portfolio is the key to your innovation engine, unlocking the tools and automation that help you scale, manage, and protect your technology environment.

• Built-in telemetry streaming, thermal management, and RESTful API with Redfish offer streamlined visibility and control for better server management

• Intelligent automation lets you enable cooperation between human actions and system capabilities for added productivity

• Integrated change management capabilities for update planning and seamless, zero-touch configuration and implementation

• Full-stack management integration with Microsoft, VMware, ServiceNow, Ansible and many other tools

Protect your data assets and infrastructure with proactive resilience

The Dell EMC PowerEdge R650 server is designed with a cyber-resilient architecture, integrating security deeply into every phase in the lifecycle, from design to retirement.

• Operate your workloads on a secure platform anchored by cryptographically trusted booting and silicon root of trust

• Maintain server firmware safety with digitally signed firmware packages

• Prevent unauthorized configuration or firmware change with system lockdown

• Securely and quickly wipe all data from storage media, including hard drives, SSDs and system memory with System Erase

4.4.4 Dell EMC PowerEdge R750 Rack Servers #

 

Note

The EMC PowerEdge R750 is SUSE YES Certified Hardware.

General purpose server optimized to address the most demanding workloads

The Dell EMC PowerEdge R750 is a full-featured enterprise server, delivering outstanding performance for the most demanding workloads

• CPU : Up to two 3rd Generation Intel Xeon Scalable processors, with up to 40 cores per processor

• Memory : 32 DDR4 DIMM slots, supports RDIMM 2 TB max or LRDIMM 8 TB max, speeds up to 3200 MT/s, Up to 16 Intel Persistent Memory 200 series (BPS) slots, 8 TB max, Supports registered ECC DDR4 DIMMs only

• Storage Controllers

  • Internal controllers : PERC H745, HBA355I, S150, H345, H755, H755N

  • Boot Optimized Storage Subsystem (BOSS-S2): HW RAID 2 x M.2 SSDs 240 GB or 480 GB

  • External PERC (RAID): PERC H840, HBA355E

• Drive Bays

  • Front bays : Up to 12 x 3.5-inch SAS/SATA (HDD/SSD) max 192 TB, Up to 8 x 2.5-inch NVMe (SSD) max 122.88 TB, Up to 16 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 245.76 TB, Up to 24 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 368.84 TB

  • Rear bays : Rear bays: Up to 2 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 30.72 TB, Up to 4 x 2.5-inch SAS/SATA/NVMe (HDD/SSD) max 61.44 TB

Tip

For more information, see see Dell EMC PowerEdge R750 Datasheet

Innovate at scale with challenging and emerging workloads

The Dell EMC PowerEdge R750, powered by the 3rd Generation Intel Xeon Scalable processors is a rack server to address application performance and acceleration. The EMC PowerEdge R750, is a dual-socket/2U rack server that delivers outstanding performance for the most demanding workloads. It supports 8 channels of memory per CPU, and up to 32 DDR4 DIMMs @ 3200 MT/s speeds. In addition, to address substantial throughput improvements the EMC PowerEdge R750 supports PCIe Gen 4 and up to 24 NVMe drives with improved air-cooling features and optional Direct Liquid Cooling to support increasing power and thermal requirements. This makes the EMC PowerEdge R750 an ideal server for data center standardization on a wide range of workloads including; Database and Analytics, Highperformance computing (HPC), Traditional corporate IT, Virtual Desktop Infrastructure, and AI/ML environments that require performance, extensive storage and GPU support

Increase efficiency and accelerate operations with autonomous collaboration

The Dell EMC OpenManage systems management portfolio tames the complexity of managing and securing IT infrastructure. Using Dell Technologies’ intuitive end-to-end tools, IT can deliver a secure, integrated experience by reducing process and information silos in order to focus on growing the business. The Dell EMC OpenManage portfolio is the key to your innovation engine, unlocking the tools and automation that help you scale, manage, and protect your technology environment.

• Built-in telemetry streaming, thermal management, and RESTful API with Redfish offer streamlined visibility and control for better server management

• Intelligent automation lets you enable cooperation between human actions and system capabilities for added productivity

• Integrated change management capabilities for update planning and seamless, zero-touch configuration and implementation

• Full-stack management integration with Microsoft, VMware, ServiceNow, Ansible and many other tool

Protect your data assets and infrastructure with proactive resilience

The Dell EMC PowerEdge R750 server is designed with a cyber-resilient architecture, integrating security deeply into every phase in the lifecycle, from design to retirement.

• Operate your workloads on a secure platform anchored by cryptographically trusted booting and silicon root of trust

• Maintain server firmware safety with digitally signed firmware packages

• Prevent unauthorized configuration or firmware change with system lockdown

• Securely and quickly wipe all data from storage media, including hard drives, SSDs and system memory with System Erase

Note

A sample bill of materials, in the Chapter 9, Appendix, cites the necessary quantites of all components, along with a reference to the minimum resource requirements needed by the software components.

This section describes the process steps for the deployment of the K3s solution. It describes the process steps to deploy each of the component layers starting as a base functional proof-of-concept, having considerations on migration toward production, providing scaling guidance that is needed to create the solution.

5.1 Deployment overview #

 

The deployment stack is represented in the following figure:

Figure 5.1: Deployment Stack - K3s #

 

and details are covered for each layer in the following sections.

Note

The following section’s content is ordered and described from the bottom layer up to the top.

Using components and offerings from SUSE and the Rancher portfolio plus Dell EMC PowerEdge Rack Servers streamline the ability to quickly and effectively engage in a digital transformation, taking advantage of cloud-native resources and disciplines. Using such technology approaches lets you deploy and leverage transformations of infrastructure into a durable, reliable enterprise-grade environment.

The following sections provide a bill of materials listing for the respective component layer(s) of the described deployment.

9.2 Software bill of materials #

 

Sample set of software, support and services.

Role	Qty	SKU	Component	Notes
Operating System	1-3	874-007864	SUSE Linux Enterprise Micro, x86_64, Priority Subscription, 1 Year	Configuration: per node (up to 16 cores, stackable)
Kubernetes Management	1	R-0001-PS1	SUSE Rancher, x86-64, Priority Subscription, 1 Year	Configuration: per deployed instance
Rancher Management	2	R-0004-PS1	Rancher 10 Nodes x86-64 or aarch64, Priority Subscription, 1 Year,	Configuration: requires priority server subscription
Consulting and Training	1	R-0001-QSO	Rancher Quick Start, Go Live Services

Note

For the software components, other support term durations are also available.

Appendix=1 ArchOv=1 Automation=1 Availability=1 BP=1 BPBV=1 CompMod=1 DepConsiderations=1 Deployment=1 FCTR=1 FLVR=1 GFDL=1 Glossary=1 HWComp=1 HWDepCfg=1 IHV-Dell-PowerEdge=1 IHV-Dell=1 Integrity=1 LN=1 PoC=1 Production=1 RA=1 RC=1 References=1 Requirements=1 SWComp=1 SWDepCfg=1 Scaling=1 Security=1 docdate=2022-03-28 env-daps=1 focusK3s=1 iIHV=1 iK3s=1 iRKE1=1 iRKE2=1 iRMT=1 iRancher=1 iSLEMicro=1 iSLES=1 iSUMa=1 layerSLEMicro=1

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If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties—​for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

Copyright (c) YEAR YOUR NAME.
   Permission is granted to copy, distribute and/or modify this document
   under the terms of the GNU Free Documentation License, Version 1.2
   or any later version published by the Free Software Foundation;
   with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
   A copy of the license is included in the section entitled “GNU
   Free Documentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “ with…​Texts.” line with this:

with the Invariant Sections being LIST THEIR TITLES, with the
   Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.