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SUSE Rancher 2.6

Kasten K10 by Veeam with SUSE Rancher

Getting Started

Abstract

This document provides a brief introduction and demonstration of Kasten K10 by Veeam with SUSE Rancher for enterprise cloud native backup/restore, disaster recovery, and app mobility.

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Disclaimer: Documents published as part of the series SUSE Technical Reference Documentation have been contributed voluntarily by SUSE employees and third parties. They are meant to serve as examples of how particular actions can be performed. They have been compiled with utmost attention to detail. However, this does not guarantee complete accuracy. SUSE cannot verify that actions described in these documents do what is claimed or whether actions described have unintended consequences. SUSE LLC, its affiliates, the authors, and the translators may not be held liable for possible errors or the consequences thereof.

Author: Adam Bergh, Solutions Architect, Cloud Native Technical Partnerships, Kasten by Veeam
Author: Terry Smith, Global Partner Solutions Director, SUSE
Author: Gerson Guevara, IHV Solutions Architect, SUSE
Publication Date: 2022-07-27

1 Introduction

1.1 Motivation

Organizations are shifting to cloud native, leveraging containerized workloads and Kubernetes management platforms like SUSE Rancher. The goal is to gain greater flexibility, scale, and resilience to accelerate innovation and quickly adjust to dynamic conditions. In this always-on IT environment, application mobility and data protection are critical considerations.

logo lockup suse rancher veeam kasten hor dark new

The Kasten K10 by Veeam® data management platform provides enterprise operations teams with an easy-to-use, scalable, and secure system for backup and restore, disaster recovery, and mobility of cloud-native applications.

1.2 Scope

This guide provides an overview of the steps to install and set up Kasten K10 by Veeam in your SUSE Rancher Kubernetes environment and to perform a simple backup and restore of an application.

1.3 Audience

This document is intended for IT operations teams, backup administrators, DevOps and DevSecOps teams, and others who are responsible for ensuring business continuity, disaster recovery, ransomware and threat reduction, and application migration for cloud native landscapes.

2 Technical overview

The Kasten K10 by Veeam® data management platform has deep integrations with SUSE Rancher and comes with an extensive ecosystem of support across Kubernetes distributions and cloud platforms. This provides enterprise operations teams the flexibility to choose the deployment environments that best meet their needs - on-premises, public cloud, and hybrid. K10 is policy-driven and extensible. It delivers enterprise features such as full-spectrum consistency, database integration, automatic application discovery, multi-cloud mobility, and a powerful web-based user interface.

rancher veeam kasten architecture 1

3 Prerequisites

For this guide, you will need the following:

  • SUSE Rancher

    In this guide, we use Rancher 2.6.

    See SUSE Rancher installation guide for more information.

  • Kubernetes cluster managed by SUSE Rancher Any CNCF-certified Kubernetes cluster can be used.

    See SUSE Rancher Support Matrix

  • Storage for backup target

    An external backup storage target, such as an NFS file server or cloud object store. This document will use an external, S3-compatible object storage bucket.

  • User application to demonstrate backup and restore capability

    For example, WordPress can be easily installed by Helm chart.

K10 can be installed in a variety of different environments. To ensure a smooth installation experience, you can use the primer tool to perform several pre-flight checks to make sure that the prerequisites are met. This tool runs in a pod in the cluster and does the following:

  • Validates that the Kubernetes settings meet the K10 requirements.

  • Catalogs the available StorageClasses.

  • If a CSI provisioner exists, it will also perform a basic validation of the cluster’s CSI capabilities and any relevant objects that may be required.

    See CSI pre-flight checks in the documentation for more details.

Run the following command to deploy the primer tool:

curl https://docs.kasten.io/tools/k10_primer.sh | bash
Note
Note

This will create and clean up a ServiceAccount and ClusterRoleBinding to perform sanity checks on your Kubernetes cluster.

4 Installing Kasten K10

Kasten K10 can be easily deployed from the SUSE Rancher Apps & Marketplace.

  1. Create a new namespace for the Kasten K10 application.

    1. In the SUSE Rancher user interface (UI), navigate to ClustersProject/Namespaces.

      rancher veeam kasten step1 1
    2. Create a "kasten-io" namespace for Kasten K10.

      rancher veeam kasten k10 create namespace
  2. Install Kasten K10.

    1. Navigate to Apps & Marketplace > Charts within the SUSE Rancher UI and search for “Kasten.”

      rancher veeam kasten k10 marketplace1
    2. Select the K10 chart and click Install.

      rancher veeam kasten k10 marketplace2
    3. Select the namespace "kasten-io” from the Namespace drop-down box. Optionally select Customize Helm options before install to customize the deployment. See the Complete list of Helm options for detailed descriptions.

      rancher veeam kasten k10 marketplace3
    4. After setting your chart values, click Next, then click Install.

  3. Validate the installation.

    To validate that Kasten K10 has been properly installed, run the following command in the "kasten-io" namespace and watch for the status of all K10 pods:

    kubectl get pods --namespace kasten-io --watch

    It may take a couple of minutes for all pods to come up and display "Running" status.

    kubectl get pods --namespace kasten-io
    
    NAMESPACE     NAME                                    READY   STATUS    RESTARTS   AGE
    kasten-io     aggregatedapis-svc-b45d98bb5-w54pr      1/1     Running   0          1m26s
    kasten-io     auth-svc-8549fc9c59-9c9fb               1/1     Running   0          1m26s
    kasten-io     catalog-svc-f64666fdf-5t5tv             2/2     Running   0          1m26s
    ...
Note
Note

In the unlikely scenario that pods are stuck in any other state, see the support documentation to debug further.

5 Accessing the K10 dashboard

The Kasten K10 dashboard is not exposed externally by default. To establish a connection, use the following kubectl command:

kubectl --namespace kasten-io port-forward service/gateway 8080:8000
Note
Note

If you installed Kasten K10 with a different release name than k10 (specified via the --name option in the install command), replace the last occurrence of "k10" in the above URL with the specified release name. The revised URL would look like http://127.0.0.1:8080/<release-name>/#/.

Note
Note

If you are running on GKE and want to access the dashboard without local kubectl access, see K10 Dashboard Directly From the Google Cloud Console.

Direct access to the K10 dashboard requires a properly configured authentication method to secure access. For more information, see Kubernetes authentication.

For this guide, we provide an overview of the steps to configure basic authentication or token authentication. Choose one of these authentication methods to proceed.

5.1 Basic authentication

Basic authentication allows you to protect access to the K10 dashboard with a user name and password.

Enable basic authentication by first generating htpasswd credentials using either an online tool or via the htpasswd command found on most systems. When generated, you need to supply the resulting string with the helm install or helm upgrade command using the following flags:

--set auth.basicAuth.enabled=true \
--set auth.basicAuth.htpasswd='example:$apr1$qrAVXu.v$Q8YVc50vtiS8KPmiyrkld0'

Alternatively, you can use an existing secret contained in a file created with htpasswd. The secret must be in the K10 namespace with the key named "auth" and the value as the password generated using htpasswd.

--set auth.basicAuth.enabled=true \
--set auth.basicAuth.secretName=my-basic-auth-secret

5.2 Token authentication

Token authentication allows the use of any token that can be verified by the Kubernetes server. For more information about token authentication, see:

  1. Enable token authentication by using the following flag as part of the initial helm install or subsequent helm upgrade command.

    --set auth.tokenAuth.enabled=true
  2. Next, provide a bearer token that will be used when accessing the dashboard.

    rancher veeam kasten k10 token login1

The most common token type that you can use is a service account bearer token.

  1. You can use kubectl to extract such a token from a service account that you know has the proper permissions.

    1. Get the SA secret

      sa_secret=$(kubectl get serviceaccount my-kasten-sa -o jsonpath="{.secrets[0].name}" --namespace kasten-io)
    2. Extract the token

      kubectl get secret $sa_secret --namespace kasten-io -ojsonpath="{.data.token}{'\n'}" | base64 --decode
  2. Alternatively, you can create a new service account from which to extract the token.

    kubectl create serviceaccount my-kasten-sa --namespace kasten-io

    In this case, you need to create a role binding or cluster role binding for the account to ensure that it has the appropriate permissions for K10. To learn more about the necessary K10 permissions, see Authorization.

5.3 Kasten K10 dashboard overview

The K10 dashboard is divided into several different sections, described below.

rancher veeam kasten k10 dashboard welcome
Tip
Tip

A guided tour of the K10 dashboard is available when the K10 dashboard is accessed for the first time or via the dashboard option on the Settings page.

The top of the K10 dashboard displays a list of applications currently mapped to namespaces, any policies that might exist in the system, and a summary of the cluster’s backup data footprint.

rancher veeam kasten k10 dashboard overview top

After filtering for applications that have stateful services (defined as containing a persistent volume), this screen further categorizes applications as:

  • Unmanaged: There are no protection policies that cover this object.

  • Non-compliant: A policy applies to this object, but the actions associated with the policy are failing (because of underlying storage slowness, configuration problems, etc.) or the actions have not been invoked yet.

  • Compliant: These objects have policies and the policy SLAs are being respected.

Tip
Tip

You can filter the view by clicking the Compliant, Non-Compliant, or Unmanaged buttons.

The K10 platform equates namespaces to applications for ease of use and consistency with Kubernetes best practices, use of role-based authentication controls (RBAC), and to mirror the most common application deployment patterns. However, as shown later, policies can be defined to operate on more than one namespace or only operate on a subset of an application residing in a single namespace.

Assuming you have already installed applications, clicking the Applications card on the dashboard will take you to the following view.

rancher veeam kasten k10 dashboard apps1

An application is made up of multiple Kubernetes resources and workloads, including deployments and stateful sets.

rancher veeam kasten k10 dashboard apps2

K10 policies are used to automate your data management workflows. Policies combine actions you want to take (such as making a snapshot), frequency or schedule for how often you want to perform the action, and selection criteria for the resources you want to manage.

rancher veeam kasten k10 dashboard overview top

When you click the Policies card in the main dashboard, you notice that no default policies are created at install time, but a policy can be either created from this page or from the application page shown earlier.

rancher veeam kasten k10 dashboard policies

6 Creating a location profile

K10 can invoke protection operations, such as snapshots, within a cluster without requiring additional credentials, and this may be sufficient if K10 is running in the major public clouds and actions are limited to a single cluster. It is not sufficient for most production situations, where performing real backups, enabling cross-cluster and cross-cloud application migration, and enabling disaster recovery are essential.

To enable these actions that span the lifetime of any one cluster, K10 needs to be configured with access to external object storage or external NFS file storage. This is accomplished with location profiles.

rancher veeam kasten k10 location profiles1

Profile creation can be accessed from the Settings icon in the top-right corner of the dashboard or via the CRD-based Profiles API. Location profiles are used to create backups from snapshots, move applications and their data across clusters and potentially across different clouds, and to subsequently import these backups or exports into another cluster.

To create a location profile, click New Profile on the profiles page.

rancher veeam kasten k10 location profiles2

When exporting to or importing from an object storage location, you are required to pick an object storage provider, a region for the bucket if being used in a public cloud, and the bucket name. If a bucket with the given name does not exist, it will be created.

If an S3-compatible object storage system is used that is not hosted by one of the supported cloud providers, an S3 endpoint URL will need to be specified and optionally, SSL verification might need to be disabled. Disabling SSL verification is only recommended for test setups.

Note
Note

When certain cloud providers (like AWS or Microsoft Azure) are selected, provider-specific options (such as IAM Roles) will appear for configuration.

When you click Validate and Save, the configuration profile will be created and a profile similar to the following will appear:

rancher veeam kasten k10 location profiles3

7 Creating a policy

Protecting an application with K10, is usually accomplished by creating a policy. Understanding these three concepts is essential:

  • Snapshots and Backups: You may require just one or both of these data capture mechanisms, depending on your environment and requirements.

  • Scheduling: You specify the application capture frequency and snapshot/backup retention to meet your objectives.

  • Selection: You identify the applications protected by a policy. You can also filter resources to restrict what is captured on a per-application basis.

This section demonstrates how to use these concepts in the context of a K10 policy to protect applications.

K10 defines an application as a collection of namespaced Kubernetes resources associated with

  • a workload (such as ConfigMaps and Secrets),

  • relevant non-namespaced resources used by the application (such as StorageClasses),

  • Kubernetes workloads (including Deployments, StatefulSets, standalone pods, etc.),

  • deployment and release information available from Helm v3,

  • and all persistent storage resources (such as PersistentVolumeClaims and PersistentVolumes).

While you can always create a policy from scratch through the policies page, the easiest way to define policies for unprotected applications is to click the Applications card in the main dashboard. This will allow you to see all applications in your Kubernetes cluster.

rancher veeam kasten k10 dashboard apps1

To protect any unmanaged application, simply click Create a Policy to open the New Policy dialog.

rancher veeam kasten k10 policies create1

7.1 Snapshots and backups

All policies center around the execution of actions. You start by selecting the snapshot action with an optional backup (called an export).

See Snapshots and Backups in the Kasten documentation for more details.

7.1.1 Snapshots

Snapshots form the basis of persistent data capture in K10. They are typically used in the context of disk volumes (PVC/PVs) used by the application but can also apply to application-level data capture (such as with Kanister).

rancher veeam kasten k10 policies create2
Note
Note

Several public cloud providers (including AWS, Azure, and Google Cloud) actually store snapshots in object storage, and they are retained independent of the lifecycle of the primary volume. However, this is not true of all public clouds, and an independent backup would provide essential safety. Check with your cloud provider’s documentation for more information.

Snapshots, in most storage systems, are very efficient and have a very low performance impact on the primary workload, require no downtime, support fast restore times, and enable incremental data capture.

Storage snapshots usually suffer from constraints, such as having relatively low limits on the maximum number of snapshots per volume or per storage array. Most importantly, snapshots are not always durable. A catastrophic storage system failure will destroy your snapshots along with your primary data. Further, in several storage systems, a snapshot’s lifecycle is tied to the source volume. So, if the volume is deleted, all related snapshots might automatically be garbage collected at the same time.

Tip
Tip

It is highly recommended that you create backups of your application snapshots to ensure durability.

7.1.2 Backups

Backups overcome the limitations of application and volume snapshots by converting them to an infrastructure-independent format, deduplicating, compressing, and encrypting them before they are stored in an external object store or NFS volume.

To convert your snapshots into backups, activate Enable Backups via Snapshot Exports during policy creation.

rancher veeam kasten k10 policies create3

7.2 Scheduling

There are four components to K10 scheduling:

  • Action frequency: how frequently the primary snapshot action should be performed

  • Export frequency: how often snapshots should be exported to backups

  • Retention schedule: how snapshots and backups are rotated and retained

  • Timing: when the primary snapshot action should be performed

7.2.1 Action frequency

Snapshots can be set to execute at an hourly, daily, weekly, monthly, or yearly frequency, or on demand. By default, hourly snapshots execute at the top of the hour, while weekly, monthly, and yearly snapshots execute at midnight UTC.

rancher veeam kasten k10 backup frequency

You can also specify the time at which scheduled actions execute and sub-frequencies that execute multiple actions per frequency. Sub-hourly actions can be useful when you are protecting mostly Kubernetes objects or small data sets. See Advanced Schedule Options in the Kasten documentation for more information.

Warning
Warning

Care should be taken not to stress the underlying storage infrastructure or running into storage API rate limits. Further, sub-frequencies do also interact with retention (described below). For example, retaining 24 hourly snapshots at 15-minute intervals would only retain 6 hours of snapshots.

7.2.2 Export frequency

When Enable Backups via Snapshot Exports is enabled, snapshots are exported as backups. By default, every snapshot is exported, but you can limit this to a subset by selecting a daily, weekly, monthly, or yearly export frequency.

rancher veeam kasten k10 export frequency

7.2.3 Retention schedule

A powerful scheduling feature in K10 is the ability to use a https://en.wikipedia.org/wiki/Backup_rotation_scheme#Grandfather-father-son [GFS retention scheme] for cost savings and compliance. With this backup rotation scheme, hourly snapshots and backups are rotated each hour with one graduating to daily every day, daily snapshots and backups are rotated each day with one graduating to weekly, and so on. It is possible to set the number of hourly, daily, weekly, monthly, and yearly copies that need to be retained, and K10 will take care of cleanup.

rancher veeam kasten k10 snapshot retention schedule
Note
Note

It is not possible to set a retention schedule for on demand policies.

By default, the backup retention schedule is the same as the snapshot retention schedule. You can make these independent schedules, if needed. This allows you to create policies where a limited number of snapshots are retained for fast recovery from accidental outages while a larger number of backups are stored for long-term recovery. This separate retention schedule is also valuable when a limited number of snapshots are supported on the volume but a larger backup retention count is needed for compliance.

rancher veeam kasten k10 backup retention schedule

Snapshots and backups created by scheduled runs of a policy can be retained and omitted from the retention counts by adding a k10.kasten.io/doNotRetire: "true" label to the RunAction created for the policy run.

Note
Note

The retention schedule for a policy does not apply to snapshots and backups produced by manual policy runs. And you will need to clean up any artifacts created by manual policy runs.

7.2.4 Timing

By default, actions set to hourly execute at the top of the hour and other action frequencies execute at midnight UTC.

Unhide Advanced Options to select how many times actions are executed within the frequency interval. For example, if the action frequency is daily, you can specify the hour of the day and the minutes after the hour when the action is to start.

rancher veeam kasten k10 timing1

You can also customize the retention schedule by selecting which snapshots and backups will graduate and be retained for longer periods.

rancher veeam kasten k10 timing2 snapshot retention
Tip
Tip

You can toggle whether to display and enter times in local time or UTC, but all times are converted to UTC and do not change for daylight savings time.

7.3 Selection

In K10, you can specify which applications are bound to a policy by name or label.

7.3.1 Application name

The most straightforward way to apply a policy to an application in K10 is to use its name (derived from the name of the namespace). You can even select multiple application names for the same policy.

If you need a policy to span similar applications, use the asterisk ('*') wild card. For example, if you specify 'mysql-*', K10 will match all applications whose names start with 'mysql-'.

rancher veeam kasten k10 selection by name wildcard
Note
Note

For policies that need to span all applications, use the asterisk wild card by itself.

7.3.2 Application label

You can also use labels to bind a policy to multiple applications. For example, you could protect all applications that use MongoDB or applications that have been annotated with, say, the 'gold' label. Matching occurs on labels applied to namespaces, deployments, and statefulsets. If multiple labels are selected, a union (logical OR) will be performed, matching all applications with at least one of the labels.

Label-based selection can be used to create forward-looking policies, as such policy would automatically apply to any future application with the matching label. For example, if you use a label of 'heritage: Tiller' (for Helm v2) or 'heritage: Helm' (for Helm v3), the selector will apply the policy to any new Helm-deployed applications because the label is applied to any Kubernetes workload created by the Helm package manager.

rancher veeam kasten k10 selection by label

7.3.3 Other resources

K10 can also protect cluster-scoped resources without targeting any applications. To specify this, select None.

rancher veeam kasten k10 selection cluster scoped

For more information about protecting cluster-scoped resources, see Cluster-Scoped Resources.

7.3.4 Customization

You can further customize what is and what is not covered under a K10 application protection policy with:

8 Working with policies

When you have created a policy and have navigated back to the main dashboard, you will see the selected applications quickly switch from unmanaged to non-compliant. That is, a policy covers the objects but no action has been taken yet. The applications will switch to compliant as snapshots and backups are run and the application enters a protected state. You can also scroll down the page to see the activity, how long each snapshot took, and the generated artifacts.

rancher veeam kasten k10 policy activity
Note
Note

More detailed job information can be obtained by clicking the in-progress or completed jobs.

8.1 Manual policy runs

It is possible to manually run a policy by clicking the run once button on the desired policy. Any artifacts created by this action will not be eligible for automatic retirement and will need to be manually cleaned up.

rancher veeam kasten k10 policy detail manual

8.2 Restoring existing applications

Restoring an application is accomplished via the Applications page. To restore an application, simply click the restore icon in the application’s card.

rancher veeam kasten k10 restore app1
Note
Note

While the UI uses the "export" term for backups, no import policy is needed to restore from a backup. Import policies are only needed when you want to restore the application into a different cluster.

Next, you can select a restore point. These are distinguished in the UI as having been generated manually or automatically through a backup policy.

rancher veeam kasten k10 restore app2

A restore point may include snapshots (native to the cluster) and backups (exported outside the cluster) with the same data. When both snapshots and backups are present, the UI provides you the option to select the instance you want to use to restore the application.

rancher veeam kasten k10 restore app3

Selecting a restore point will bring up a side-panel containing more details on the restore point for you to preview before you initiate an application restore.

rancher veeam kasten k10 restore app4

When you click Restore, the system automatically re-creates the entire application stack into the selected namespace. This not only includes data associated with the original application but also the versioned container images.

Note
Note

Restored PersistentVolumes may not have the annotations specified in the original PersistentVolume.

After the restore completes, you can go back to your application and verify that the state was restored to what existed at the time the restore point was obtained.

8.3 Restoring deleted applications

Restoring a deleted application follows nearly the same process, except that removed applications are not shown on the Applications page by default. To discover them, you simply need to filter and select Removed.

rancher veeam kasten k10 restore deleted app

When the filter is in effect, you see applications that K10 has previously protected but which no longer exist. These can now be restored using the normal restore workflow.

9 Summary

SUSE Rancher enables enterprises to streamline multi-cluster Kubernetes operations everywhere with unified security, policy, and user management. Kasten K10 by Veeam delivers easy-to-use, Kubernetes native application backup and restore, disaster recovery, and application mobility. Together, SUSE and Veeam provide enterprises with the tools they need to reduce risk and accelerate cloud native success.

In this guide, you learned how to seamlessly deploy Kasten K10 into your Rancher Kubernetes landscape, create policy-driven backups, and restore applications.

Continue your journey with these additional resources:

11 GNU Free Documentation License

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3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

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.

4. MODIFICATIONS

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:

  1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

  2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.

  3. State on the Title page the name of the publisher of the Modified Version, as the publisher.

  4. Preserve all the copyright notices of the Document.

  5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

  6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

  7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.

  8. Include an unaltered copy of this License.

  9. Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

  10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

  11. For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

  12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

  13. Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.

  14. Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.

  15. Preserve any Warranty Disclaimers.

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.

5. COMBINING DOCUMENTS

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".

6. COLLECTIONS OF DOCUMENTS

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.

7. AGGREGATION WITH INDEPENDENT WORKS

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.

8. TRANSLATION

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.

9. TERMINATION

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.

10. FUTURE REVISIONS OF THIS LICENSE

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.

ADDENDUM: How to use this License for your documents

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.

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