Documentation style overview

• 1: Documentation Content Guide
• 2: Documentation Style Guide
• 3: Diagram Guide
• 4: Writing a new topic
• 5: Page content types
• 6: Content organization
• 7: Custom Hugo Shortcodes

1 - Documentation Content Guide

This page contains guidelines for Kubernetes documentation.

If you have questions about what's allowed, join the #sig-docs channel in Kubernetes Slack and ask!

You can register for Kubernetes Slack at https://slack.k8s.io/.

For information on creating new content for the Kubernetes docs, follow the style guide.

Overview

Source for the Kubernetes website, including the docs, resides in the kubernetes/website repository.

Located in the kubernetes/website/content/<language_code>/docs folder, the majority of Kubernetes documentation is specific to the Kubernetes project.

What's allowed

Kubernetes docs allow content for third-party projects only when:

• Content documents software in the Kubernetes project
• Content documents software that's out of project but necessary for Kubernetes to function
• Content is canonical on kubernetes.io, or links to canonical content elsewhere

Third party content

Kubernetes documentation includes applied examples of projects in the Kubernetes project—projects that live in the kubernetes and kubernetes-sigs GitHub organizations.

Links to active content in the Kubernetes project are always allowed.

Kubernetes requires some third party content to function. Examples include container runtimes (containerd, CRI-O, Docker), networking policy (CNI plugins), Ingress controllers, and logging.

Docs can link to third-party open source software (OSS) outside the Kubernetes project only if it's necessary for Kubernetes to function.

Dual sourced content

Wherever possible, Kubernetes docs link to canonical sources instead of hosting dual-sourced content.

Dual-sourced content requires double the effort (or more!) to maintain and grows stale more quickly.

More information

If you have questions about allowed content, join the Kubernetes Slack #sig-docs channel and ask!

What's next

• Read the Style guide.

2 - Documentation Style Guide

This page gives writing style guidelines for the Kubernetes documentation. These are guidelines, not rules. Use your best judgment, and feel free to propose changes to this document in a pull request.

For additional information on creating new content for the Kubernetes documentation, read the Documentation Content Guide.

Changes to the style guide are made by SIG Docs as a group. To propose a change or addition, add it to the agenda for an upcoming SIG Docs meeting, and attend the meeting to participate in the discussion.

Language

Kubernetes documentation has been translated into multiple languages (see Localization READMEs).

The way of localizing the docs for a different language is described in Localizing Kubernetes Documentation.

The English-language documentation uses U.S. English spelling and grammar.

Documentation formatting standards

Use upper camel case for API objects

When you refer specifically to interacting with an API object, use UpperCamelCase, also known as Pascal case. You may see different capitalization, such as "configMap", in the API Reference. When writing general documentation, it's better to use upper camel case, calling it "ConfigMap" instead.

When you are generally discussing an API object, use sentence-style capitalization.

The following examples focus on capitalization. For more information about formatting API object names, review the related guidance on Code Style.

Use angle brackets for placeholders

Use angle brackets for placeholders. Tell the reader what a placeholder represents, for example:

Display information about a pod:

kubectl describe pod <pod-name> -n <namespace>

If the namespace of the pod is default, you can omit the '-n' parameter.

Use bold for user interface elements

Use italics to define or introduce new terms

Use code style for filenames, directories, and paths

Use the international standard for punctuation inside quotes

Inline code formatting

Use code style for inline code, commands

For inline code in an HTML document, use the <code> tag. In a Markdown document, use the backtick (`). However, API kinds such as StatefulSet or ConfigMap are written verbatim (no backticks); this allows using possessive apostrophes.

Use code style for object field names and namespaces

Use code style for Kubernetes command tool and component names

Starting a sentence with a component tool or component name

Use a general descriptor over a component name

Use normal style for string and integer field values

For field values of type string or integer, use normal style without quotation marks.

However, consider quoting values where there is a risk that readers might confuse the value with an API kind.

Referring to Kubernetes API resources

This section talks about how we reference API resources in the documentation.

Clarification about "resource"

Kubernetes uses the word resource to refer to API resources. For example, the URL path /apis/apps/v1/namespaces/default/deployments/my-app represents a Deployment named "my-app" in the "default" namespace. In HTTP jargon, namespace is a resource - the same way that all web URLs identify a resource.

Kubernetes documentation also uses "resource" to talk about CPU and memory requests and limits. It's very often a good idea to refer to API resources as "API resources"; that helps to avoid confusion with CPU and memory resources, or with other kinds of resource.

If you are using the lowercase plural form of a resource name, such as deployments or configmaps, provide extra written context to help readers understand what you mean. If you are using the term in a context where the UpperCamelCase name could work too, and there is a risk of ambiguity, consider using the API kind in UpperCamelCase.

When to use Kubernetes API terminologies

The different Kubernetes API terminologies are:

• API kinds: the name used in the API URL (such as pods, namespaces). API kinds are sometimes also called resource types.
• API resource: a single instance of an API kind (such as pod, secret).
• Object: a resource that serves as a "record of intent". An object is a desired state for a specific part of your cluster, which the Kubernetes control plane tries to maintain. All objects in the Kubernetes API are also resources.

For clarity, you can add "resource" or "object" when referring to an API resource in Kubernetes documentation. An example: write "a Secret object" instead of "a Secret". If it is clear just from the capitalization, you don't need to add the extra word.

Consider rephrasing when that change helps avoid misunderstandings. A common situation is when you want to start a sentence with an API kind, such as “Secret”; because English and other languages capitalize at the start of sentences, readers cannot tell whether you mean the API kind or the general concept. Rewording can help.

API resource names

Always format API resource names using UpperCamelCase, also known as PascalCase. Do not write API kinds with code formatting.

Don't split an API object name into separate words. For example, use PodTemplateList, not Pod Template List.

For more information about PascalCase and code formatting, review the related guidance on Use upper camel case for API objects and Use code style for inline code, commands, and API objects.

For more information about Kubernetes API terminologies, review the related guidance on Kubernetes API terminology.

Code snippet formatting

Don't include the command prompt

Separate commands from output

Verify that the pod is running on your chosen node:

kubectl get pods --output=wide

The output is similar to this:

NAME     READY     STATUS    RESTARTS   AGE    IP           NODE
nginx    1/1       Running   0          13s    10.200.0.4   worker0

Versioning Kubernetes examples

Code examples and configuration examples that include version information should be consistent with the accompanying text.

If the information is version specific, the Kubernetes version needs to be defined in the prerequisites section of the Task template or the Tutorial template. Once the page is saved, the prerequisites section is shown as Before you begin.

To specify the Kubernetes version for a task or tutorial page, include min-kubernetes-server-version in the front matter of the page.

If the example YAML is in a standalone file, find and review the topics that include it as a reference. Verify that any topics using the standalone YAML have the appropriate version information defined. If a stand-alone YAML file is not referenced from any topics, consider deleting it instead of updating it.

For example, if you are writing a tutorial that is relevant to Kubernetes version 1.8, the front-matter of your markdown file should look something like:

---
title: <your tutorial title here>
min-kubernetes-server-version: v1.8
---

In code and configuration examples, do not include comments about alternative versions. Be careful to not include incorrect statements in your examples as comments, such as:

apiVersion: v1 # earlier versions use...
kind: Pod
...

Kubernetes.io word list

A list of Kubernetes-specific terms and words to be used consistently across the site.

Shortcodes

Hugo Shortcodes help create different rhetorical appeal levels. Our documentation supports three different shortcodes in this category: Note {{< note >}}, Caution {{< caution >}}, and Warning {{< warning >}}.

1. Surround the text with an opening and closing shortcode.

2. Use the following syntax to apply a style:

   {{< note >}}
   No need to include a prefix; the shortcode automatically provides one. (Note:, Caution:, etc.)
   {{< /note >}}
   

   The output is:

   Note:

   The prefix you choose is the same text for the tag.

Note

Use {{< note >}} to highlight a tip or a piece of information that may be helpful to know.

For example:

{{< note >}}
You can _still_ use Markdown inside these callouts.
{{< /note >}}

The output is:

You can use a {{< note >}} in a list:

1. Use the note shortcode in a list

1. A second item with an embedded note

   {{< note >}}
   Warning, Caution, and Note shortcodes, embedded in lists, need to be indented four spaces. See [Common Shortcode Issues](#common-shortcode-issues).
   {{< /note >}}

1. A third item in a list

1. A fourth item in a list

The output is:

1. Use the note shortcode in a list

2. A second item with an embedded note

   Note:

   Warning, Caution, and Note shortcodes, embedded in lists, need to be indented four spaces. See [Common Shortcode Issues](#common-shortcode-issues).
   

3. A third item in a list

4. A fourth item in a list

Caution

Use {{< caution >}} to call attention to an important piece of information to avoid pitfalls.

For example:

{{< caution >}}
The callout style only applies to the line directly above the tag.
{{< /caution >}}

The output is:

Warning

Use {{< warning >}} to indicate danger or a piece of information that is crucial to follow.

For example:

{{< warning >}}
Beware.
{{< /warning >}}

The output is:

Common Shortcode Issues

Ordered Lists

Shortcodes will interrupt numbered lists unless you indent four spaces before the notice and the tag.

For example:

1. Preheat oven to 350˚F

1. Prepare the batter, and pour into springform pan.
   {{< note >}}Grease the pan for best results.{{< /note >}}

1. Bake for 20-25 minutes or until set.

The output is:

1. Preheat oven to 350˚F

2. Prepare the batter, and pour into springform pan.

   Note:

   Grease the pan for best results.

3. Bake for 20-25 minutes or until set.

Include Statements

Shortcodes inside include statements will break the build. You must insert them in the parent document, before and after you call the include. For example:

{{< note >}}
{{< include "task-tutorial-prereqs.md" >}}
{{< /note >}}

Markdown elements

Line breaks

Use a single newline to separate block-level content like headings, lists, images, code blocks, and others. The exception is second-level headings, where it should be two newlines. Second-level headings follow the first-level (or the title) without any preceding paragraphs or texts. A two line spacing helps visualize the overall structure of content in a code editor better.

Manually wrap paragraphs in the Markdown source when appropriate. Since the git tool and the GitHub website generate file diffs on a line-by-line basis, manually wrapping long lines helps the reviewers to easily find out the changes made in a PR and provide feedback. It also helps the downstream localization teams where people track the upstream changes on a per-line basis. Line wrapping can happen at the end of a sentence or a punctuation character, for example. One exception to this is that a Markdown link or a shortcode is expected to be in a single line.

Headings and titles

People accessing this documentation may use a screen reader or other assistive technology (AT). Screen readers are linear output devices, they output items on a page one at a time. If there is a lot of content on a page, you can use headings to give the page an internal structure. A good page structure helps all readers to easily navigate the page or filter topics of interest.

Paragraphs

Links

Lists

Group items in a list that are related to each other and need to appear in a specific order or to indicate a correlation between multiple items. When a screen reader comes across a list—whether it is an ordered or unordered list—it will be announced to the user that there is a group of list items. The user can then use the arrow keys to move up and down between the various items in the list. Website navigation links can also be marked up as list items; after all they are nothing but a group of related links.

• End each item in a list with a period if one or more items in the list are complete sentences. For the sake of consistency, normally either all items or none should be complete sentences.

  Note:

  Ordered lists that are part of an incomplete introductory sentence can be in lowercase and punctuated as if each item was a part of the introductory sentence.

• Use the number one (1.) for ordered lists.

• Use (+), (*), or (-) for unordered lists.

• Leave a blank line after each list.

• Indent nested lists with four spaces (for example, ⋅⋅⋅⋅).

• List items may consist of multiple paragraphs. Each subsequent paragraph in a list item must be indented by either four spaces or one tab.

Tables

The semantic purpose of a data table is to present tabular data. Sighted users can quickly scan the table but a screen reader goes through line by line. A table caption is used to create a descriptive title for a data table. Assistive technologies (AT) use the HTML table caption element to identify the table contents to the user within the page structure.

• Add table captions using Hugo shortcodes for tables.

Content best practices

This section contains suggested best practices for clear, concise, and consistent content.

Use present tense

Exception: Use future or past tense if it is required to convey the correct meaning.

Use active voice

Exception: Use passive voice if active voice leads to an awkward construction.

Use simple and direct language

Use simple and direct language. Avoid using unnecessary phrases, such as saying "please."

Address the reader as "you"

Avoid Latin phrases

Prefer English terms over Latin abbreviations.

Exception: Use "etc." for et cetera.

Patterns to avoid

Avoid using "we"

Using "we" in a sentence can be confusing, because the reader might not know whether they're part of the "we" you're describing.

Avoid jargon and idioms

Some readers speak English as a second language. Avoid jargon and idioms to help them understand better.

Avoid statements about the future

Avoid making promises or giving hints about the future. If you need to talk about an alpha feature, put the text under a heading that identifies it as alpha information.

An exception to this rule is documentation about announced deprecations targeting removal in future versions. One example of documentation like this is the Deprecated API migration guide.

Avoid statements that will soon be out of date

Avoid words like "currently" and "new." A feature that is new today might not be considered new in a few months.

Avoid words that assume a specific level of understanding

Avoid words such as "just", "simply", "easy", "easily", or "simple". These words do not add value.

EditorConfig file

The Kubernetes project maintains an EditorConfig file that sets common style preferences in text editors such as VS Code. You can use this file if you want to ensure that your contributions are consistent with the rest of the project. To view the file, refer to .editorconfig in the repository root.

What's next

• Learn about writing a new topic.
• Learn about using page templates.
• Learn about custom hugo shortcodes.
• Learn about creating a pull request.

3 - Diagram Guide

This guide shows you how to create, edit and share diagrams using the Mermaid JavaScript library. Mermaid.js allows you to generate diagrams using a simple markdown-like syntax inside Markdown files. You can also use Mermaid to generate .svg or .png image files that you can add to your documentation.

The target audience for this guide is anybody wishing to learn about Mermaid and/or how to create and add diagrams to Kubernetes documentation.

Figure 1 outlines the topics covered in this section.

Figure 1. Topics covered in this section.

All you need to begin working with Mermaid is the following:

• Basic understanding of markdown.
• Using the Mermaid live editor.
• Using Hugo shortcodes.
• Using the Hugo {{< figure >}} shortcode.
• Performing Hugo local previews.
• Familiar with the Contributing new content process.

Why you should use diagrams in documentation

Diagrams improve documentation clarity and comprehension. There are advantages for both the user and the contributor.

The user benefits include:

• Friendly landing spot. A detailed text-only greeting page could intimidate users, in particular, first-time Kubernetes users.
• Faster grasp of concepts. A diagram can help users understand the key points of a complex topic. Your diagram can serve as a visual learning guide to dive into the topic details.
• Better retention. For some, it is easier to recall pictures rather than text.

The contributor benefits include:

• Assist in developing the structure and content of your contribution. For example, you can start with a simple diagram covering the high-level points and then dive into details.
• Expand and grow the user community. Easily consumed documentation augmented with diagrams attracts new users who might previously have been reluctant to engage due to perceived complexities.

You should consider your target audience. In addition to experienced K8s users, you will have many who are new to Kubernetes. Even a simple diagram can assist new users in absorbing Kubernetes concepts. They become emboldened and more confident to further explore Kubernetes and the documentation.

Mermaid

Mermaid is an open source JavaScript library that allows you to create, edit and easily share diagrams using a simple, markdown-like syntax configured inline in Markdown files.

The following lists features of Mermaid:

• Simple code syntax.
• Includes a web-based tool allowing you to code and preview your diagrams.
• Supports multiple formats including flowchart, state and sequence.
• Easy collaboration with colleagues by sharing a per-diagram URL.
• Broad selection of shapes, lines, themes and styling.

The following lists advantages of using Mermaid:

• No need for separate, non-Mermaid diagram tools.
• Adheres to existing PR workflow. You can think of Mermaid code as just Markdown text included in your PR.
• Simple tool builds simple diagrams. You don't want to get bogged down (re)crafting an overly complex and detailed picture. Keep it simple!

Mermaid provides a simple, open and transparent method for the SIG communities to add, edit and collaborate on diagrams for new or existing documentation.

Live editor

The Mermaid live editor is a web-based tool that enables you to create, edit and review diagrams.

The following lists live editor functions:

• Displays Mermaid code and rendered diagram.
• Generates a URL for each saved diagram. The URL is displayed in the URL field of your browser. You can share the URL with colleagues who can access and modify the diagram.
• Option to download .svg or .png files.

Methods for creating diagrams

Figure 2 outlines the three methods to generate and add diagrams.

Figure 2. Methods to create diagrams.

Inline

Figure 3 outlines the steps to follow for adding a diagram using the Inline method.

Figure 3. Inline Method steps.

The following lists the steps you should follow for adding a diagram using the Inline method:

1. Create your diagram using the live editor.
2. Store the diagram URL somewhere for later access.
3. Copy the mermaid code to the location in your .md file where you want the diagram to appear.
4. Add a caption below the diagram using Markdown text.

A Hugo build runs the Mermaid code and turns it into a diagram.

Here is a sample code snippet contained in an .md file:

---
title: My PR
---
Figure 17 shows a simple A to B process.
some markdown text
...
{{< mermaid >}} 
    graph TB
    A --> B
{{< /mermaid >}}

Figure 17. A to B
more text

For more details on diagram captions, see How to use captions.

The following lists advantages of the Inline method:

• Live editor tool.
• Easy to copy Mermaid code to and from the live editor and your .md file.
• No need for separate .svg image file handling.
• Content text, diagram code and diagram caption contained in the same .md file.

You should use the local and Netlify previews to verify the diagram is properly rendered.

Mermaid+SVG

Figure 4 outlines the steps to follow for adding a diagram using the Mermaid+SVG method.

Figure 4. Mermaid+SVG method steps.

The following lists the steps you should follow for adding a diagram using the Mermaid+SVG method:

1. Create your diagram using the live editor.
2. Store the diagram URL somewhere for later access.
3. Generate an .svg image file for the diagram and download it to the appropriate images/ folder.
4. Use the {{< figure >}} shortcode to reference the diagram in the .md file.
5. Add a caption using the {{< figure >}} shortcode's caption parameter.

For example, use the live editor to create a diagram called boxnet. Store the diagram URL somewhere for later access. Generate and download a boxnet.svg file to the appropriate ../images/ folder.

Use the {{< figure >}} shortcode in your PR's .md file to reference the .svg image file and add a caption.

{{< figure src="/static/images/boxnet.svg" alt="Boxnet figure" class="diagram-large" caption="Figure 14. Boxnet caption" >}}

For more details on diagram captions, see How to use captions.

Note:

The

shortcode is the preferred method for adding .svg image files to your documentation. You can also use the standard markdown image syntax like so: ![my boxnet diagram](static/images/boxnet.svg). And you will need to add a caption below the diagram.

You should add the live editor URL as a comment block in the .svg image file using a text editor. For example, you would include the following at the beginning of the .svg image file:

<!-- To view or edit the mermaid code, use the following URL: -->
<!-- https://mermaid-js.github.io/mermaid-live-editor/edit/#eyJjb ... <remainder of the URL> -->

The following lists advantages of the Mermaid+SVG method:

• Live editor tool.
• Live editor tool supports the most current Mermaid feature set.
• Employ existing kubernetes/website methods for handling .svg image files.
• Environment doesn't require Mermaid support.

Be sure to check that your diagram renders properly using the local and Netlify previews.

External tool

Figure 5 outlines the steps to follow for adding a diagram using the External Tool method.

First, use your external tool to create the diagram and save it as an .svg or .png image file. After that, use the same steps as the Mermaid+SVG method for adding .svg image files.

Figure 5. External Tool method steps

The following lists the steps you should follow for adding a diagram using the External Tool method:

1. Use your external tool to create a diagram.
2. Save the diagram coordinates for contributor access. For example, your tool may offer a link to the diagram image, or you could place the source code file, such as an .xml file, in a public repository for later contributor access.
3. Generate and save the diagram as an .svg or .png image file. Download this file to the appropriate ../images/ folder.
4. Use the {{< figure >}} shortcode to reference the diagram in the .md file.
5. Add a caption using the {{< figure >}} shortcode's caption parameter.

Here is the {{< figure >}} shortcode for the images/apple.svg diagram:

{{< figure src="/static/images/apple.svg" alt="red-apple-figure" class="diagram-large" caption="Figure 9. A Big Red Apple" >}} 

If your external drawing tool permits:

• You can incorporate multiple .svg or .png logos, icons and images into your diagram. However, make sure you observe copyright and follow the Kubernetes documentation guidelines on the use of third party content.
• You should save the diagram source coordinates for later contributor access. For example, your tool may offer a link to the diagram image, or you could place the source code file, such as an .xml file, somewhere for contributor access.

For more information on K8s and CNCF logos and images, check out CNCF Artwork.

The following lists advantages of the External Tool method:

• Contributor familiarity with external tool.
• Diagrams require more detail than what Mermaid can offer.

Don't forget to check that your diagram renders correctly using the local and Netlify previews.

Examples

This section shows several examples of Mermaid diagrams.

Example 1 - Pod topology spread constraints

Figure 6 shows the diagram appearing in the Pod topology spread constraints page.

Figure 6. Pod Topology Spread Constraints.

Code block:

graph TB
   subgraph "zoneB"
       n3(Node3)
       n4(Node4)
   end
   subgraph "zoneA"
       n1(Node1)
       n2(Node2)
   end
 
   classDef plain fill:#ddd,stroke:#fff,stroke-width:4px,color:#000;
   classDef k8s fill:#326ce5,stroke:#fff,stroke-width:4px,color:#fff;
   classDef cluster fill:#fff,stroke:#bbb,stroke-width:2px,color:#326ce5;
   class n1,n2,n3,n4 k8s;
   class zoneA,zoneB cluster;

Example 2 - Ingress

Figure 7 shows the diagram appearing in the What is Ingress page.

Code block:

graph LR;
 client([client])-. Ingress-managed <br> load balancer .->ingress[Ingress];
 ingress-->|routing rule|service[Service];
 subgraph cluster
 ingress;
 service-->pod1[Pod];
 service-->pod2[Pod];
 end
 classDef plain fill:#ddd,stroke:#fff,stroke-width:4px,color:#000;
 classDef k8s fill:#326ce5,stroke:#fff,stroke-width:4px,color:#fff;
 classDef cluster fill:#fff,stroke:#bbb,stroke-width:2px,color:#326ce5;
 class ingress,service,pod1,pod2 k8s;
 class client plain;
 class cluster cluster;

Example 3 - K8s system flow

Figure 8 depicts a Mermaid sequence diagram showing the system flow between K8s components to start a container.

Code block:

%%{init:{"theme":"neutral"}}%%
sequenceDiagram
    actor me
    participant apiSrv as control plane<br><br>api-server
    participant etcd as control plane<br><br>etcd datastore
    participant cntrlMgr as control plane<br><br>controller<br>manager
    participant sched as control plane<br><br>scheduler
    participant kubelet as node<br><br>kubelet
    participant container as node<br><br>container<br>runtime
    me->>apiSrv: 1. kubectl create -f pod.yaml
    apiSrv-->>etcd: 2. save new state
    cntrlMgr->>apiSrv: 3. check for changes
    sched->>apiSrv: 4. watch for unassigned pods(s)
    apiSrv->>sched: 5. notify about pod w nodename=" "
    sched->>apiSrv: 6. assign pod to node
    apiSrv-->>etcd: 7. save new state
    kubelet->>apiSrv: 8. look for newly assigned pod(s)
    apiSrv->>kubelet: 9. bind pod to node
    kubelet->>container: 10. start container
    kubelet->>apiSrv: 11. update pod status
    apiSrv-->>etcd: 12. save new state

How to style diagrams

You can style one or more diagram elements using well-known CSS nomenclature. You accomplish this using two types of statements in the Mermaid code.

• classDef defines a class of style attributes.
• class defines one or more elements to apply the class to.

In the code for figure 7, you can see examples of both.

classDef k8s fill:#326ce5,stroke:#fff,stroke-width:4px,color:#fff; // defines style for the k8s class
class ingress,service,pod1,pod2 k8s; // k8s class is applied to elements ingress, service, pod1 and pod2.

You can include one or multiple classDef and class statements in your diagram. You can also use the official K8s #326ce5 hex color code for K8s components in your diagram.

For more information on styling and classes, see Mermaid Styling and classes docs.

How to use captions

A caption is a brief description of a diagram. A title or a short description of the diagram are examples of captions. Captions aren't meant to replace explanatory text you have in your documentation. Rather, they serve as a "context link" between that text and your diagram.

The combination of some text and a diagram tied together with a caption help provide a concise representation of the information you wish to convey to the user.

Without captions, you are asking the user to scan the text above or below the diagram to figure out a meaning. This can be frustrating for the user.

Figure 9 lays out the three components for proper captioning: diagram, diagram caption and the diagram referral.

Diagram

The Mermaid+SVG and External Tool methods generate .svg image files.

Here is the {{< figure >}} shortcode for the diagram defined in an .svg image file saved to /images/docs/components-of-kubernetes.svg:

{{< figure src="/images/docs/components-of-kubernetes.svg" alt="Kubernetes pod running inside a cluster" class="diagram-large" caption="Figure 4. Kubernetes Architecture Components >}}

You should pass the src, alt, class and caption values into the {{< figure >}} shortcode. You can adjust the size of the diagram using diagram-large, diagram-medium and diagram-small classes.

Note:

Diagrams created using the Inline method don't use the

shortcode. The Mermaid code defines how the diagram will render on your page.

See Methods for creating diagrams for more information on the different methods for creating diagrams.

Diagram Caption

Next, add a diagram caption.

If you define your diagram in an .svg image file, then you should use the {{< figure >}} shortcode's caption parameter.

{{< figure src="/images/docs/components-of-kubernetes.svg" alt="Kubernetes pod running inside a cluster" class="diagram-large" caption="Figure 4. Kubernetes Architecture Components" >}}

If you define your diagram using inline Mermaid code, then you should use Markdown text.

Figure 4. Kubernetes Architecture Components

The following lists several items to consider when adding diagram captions:

• Use the {{< figure >}} shortcode to add a diagram caption for Mermaid+SVG and External Tool diagrams.
• Use simple Markdown text to add a diagram caption for the Inline method.
• Prepend your diagram caption with Figure NUMBER.. You must use Figure and the number must be unique for each diagram in your documentation page. Add a period after the number.
• Add your diagram caption text after the Figure NUMBER. on the same line. You must puncuate the caption with a period. Keep the caption text short.
• Position your diagram caption BELOW your diagram.

Diagram Referral

Finally, you can add a diagram referral. This is used inside your text and should precede the diagram itself. It allows a user to connect your text with the associated diagram. The Figure NUMBER in your referral and caption must match.

You should avoid using spatial references such as ..the image below.. or ..the following figure ..

Here is an example of a diagram referral:

Figure 10 depicts the components of the Kubernetes architecture.
The control plane ...

Diagram referrals are optional and there are cases where they might not be suitable. If you are not sure, add a diagram referral to your text to see if it looks and sounds okay. When in doubt, use a diagram referral.

Complete picture

Figure 10 shows the Kubernetes Architecture diagram that includes the diagram, diagram caption and diagram referral. The {{< figure >}} shortcode renders the diagram, adds the caption and includes the optional link parameter so you can hyperlink the diagram. The diagram referral is contained in this paragraph.

Here is the {{< figure >}} shortcode for this diagram:

{{< figure src="/images/docs/components-of-kubernetes.svg" alt="Kubernetes pod running inside a cluster" class="diagram-large" caption="Figure 10. Kubernetes Architecture." link="https://kubernetes.io/docs/concepts/overview/components/" >}}

Tips

• Always use the live editor to create/edit your diagram.

• Always use Hugo local and Netlify previews to check out how the diagram appears in the documentation.

• Include diagram source pointers such as a URL, source code location, or indicate the code is self-documenting.

• Always use diagram captions.

• Very helpful to include the diagram .svg or .png image and/or Mermaid source code in issues and PRs.

• With the Mermaid+SVG and External Tool methods, use .svg image files because they stay sharp when you zoom in on the diagram.

• Best practice for .svg files is to load it into an SVG editing tool and use the "Convert text to paths" function. This ensures that the diagram renders the same on all systems, regardless of font availability and font rendering support.

• No Mermaid support for additional icons or artwork.

• Hugo Mermaid shortcodes don't work in the live editor.

• Any time you modify a diagram in the live editor, you must save it to generate a new URL for the diagram.

• Click on the diagrams in this section to view the code and diagram rendering in the live editor.

• Look over the source code of this page, diagram-guide.md, for more examples.

• Check out the Mermaid docs for explanations and examples.

Most important, Keep Diagrams Simple. This will save time for you and fellow contributors, and allow for easier reading by new and experienced users.

4 - Writing a new topic

This page shows how to create a new topic for the Kubernetes docs.

Before you begin

Create a fork of the Kubernetes documentation repository as described in Open a PR.

Choosing a page type

As you prepare to write a new topic, think about the page type that would fit your content the best:

Creating a new page

Use a content type for each new page that you write. The docs site provides templates or Hugo archetypes to create new content pages. To create a new type of page, run hugo new with the path to the file you want to create. For example:

hugo new docs/concepts/my-first-concept.md

Choosing a title and filename

Choose a title that has the keywords you want search engines to find. Create a filename that uses the words in your title separated by hyphens. For example, the topic with title Using an HTTP Proxy to Access the Kubernetes API has filename http-proxy-access-api.md. You don't need to put "kubernetes" in the filename, because "kubernetes" is already in the URL for the topic, for example:

   /docs/tasks/extend-kubernetes/http-proxy-access-api/

Adding the topic title to the front matter

In your topic, put a title field in the front matter. The front matter is the YAML block that is between the triple-dashed lines at the top of the page. Here's an example:

---
title: Using an HTTP Proxy to Access the Kubernetes API
---

Choosing a directory

Depending on your page type, put your new file in a subdirectory of one of these:

• /content/en/docs/tasks/
• /content/en/docs/tutorials/
• /content/en/docs/concepts/

You can put your file in an existing subdirectory, or you can create a new subdirectory.

Placing your topic in the table of contents

The table of contents is built dynamically using the directory structure of the documentation source. The top-level directories under /content/en/docs/ create top-level navigation, and subdirectories each have entries in the table of contents.

Each subdirectory has a file _index.md, which represents the "home" page for a given subdirectory's content. The _index.md does not need a template. It can contain overview content about the topics in the subdirectory.

Other files in a directory are sorted alphabetically by default. This is almost never the best order. To control the relative sorting of topics in a subdirectory, set the weight: front-matter key to an integer. Typically, we use multiples of 10, to account for adding topics later. For instance, a topic with weight 10 will come before one with weight 20.

Embedding code in your topic

If you want to include some code in your topic, you can embed the code in your file directly using the markdown code block syntax. This is recommended for the following cases (not an exhaustive list):

• The code shows the output from a command such as kubectl get deploy mydeployment -o json | jq '.status'.
• The code is not generic enough for users to try out. As an example, you can embed the YAML file for creating a Pod which depends on a specific FlexVolume implementation.
• The code is an incomplete example because its purpose is to highlight a portion of a larger file. For example, when describing ways to customize a RoleBinding, you can provide a short snippet directly in your topic file.
• The code is not meant for users to try out due to other reasons. For example, when describing how a new attribute should be added to a resource using the kubectl edit command, you can provide a short example that includes only the attribute to add.

Including code from another file

Another way to include code in your topic is to create a new, complete sample file (or group of sample files) and then reference the sample from your topic. Use this method to include sample YAML files when the sample is generic and reusable, and you want the reader to try it out themselves.

When adding a new standalone sample file, such as a YAML file, place the code in one of the <LANG>/examples/ subdirectories where <LANG> is the language for the topic. In your topic file, use the code_sample shortcode:

{{% code_sample file="<RELPATH>/my-example-yaml>" %}}

where <RELPATH> is the path to the file to include, relative to the examples directory. The following Hugo shortcode references a YAML file located at /content/en/examples/pods/storage/gce-volume.yaml.

{{% code_sample file="pods/storage/gce-volume.yaml" %}}

Showing how to create an API object from a configuration file

If you need to demonstrate how to create an API object based on a configuration file, place the configuration file in one of the subdirectories under <LANG>/examples.

In your topic, show this command:

kubectl create -f https://k8s.io/examples/pods/storage/gce-volume.yaml

For an example of a topic that uses this technique, see Running a Single-Instance Stateful Application.

Adding images to a topic

Put image files in the /images directory. The preferred image format is SVG.

What's next

• Learn about using page content types.
• Learn about creating a pull request.

5 - Page content types

The Kubernetes documentation follows several types of page content:

• Concept
• Task
• Tutorial
• Reference

Content sections

Each page content type contains a number of sections defined by Markdown comments and HTML headings. You can add content headings to your page with the heading shortcode. The comments and headings help maintain the structure of the page content types.

Examples of Markdown comments defining page content sections:

<!-- overview -->

<!-- body -->

To create common headings in your content pages, use the heading shortcode with a heading string.

Examples of heading strings:

• whatsnext
• prerequisites
• objectives
• cleanup
• synopsis
• seealso
• options

For example, to create a whatsnext heading, add the heading shortcode with the "whatsnext" string:

## {{% heading "whatsnext" %}}

You can declare a prerequisites heading as follows:

## {{% heading "prerequisites" %}}

The heading shortcode expects one string parameter. The heading string parameter matches the prefix of a variable in the i18n/<lang>.toml files. For example:

i18n/en.toml:

[whatsnext_heading]
other = "What's next"

i18n/ko.toml:

[whatsnext_heading]
other = "다음 내용"

Content types

Each content type informally defines its expected page structure. Create page content with the suggested page sections.

Concept

A concept page explains some aspect of Kubernetes. For example, a concept page might describe the Kubernetes Deployment object and explain the role it plays as an application once it is deployed, scaled, and updated. Typically, concept pages don't include sequences of steps, but instead provide links to tasks or tutorials.

To write a new concept page, create a Markdown file in a subdirectory of the /content/en/docs/concepts directory, with the following characteristics:

Concept pages are divided into three sections:

The overview and body sections appear as comments in the concept page. You can add the whatsnext section to your page with the heading shortcode.

Fill each section with content. Follow these guidelines:

• Organize content with H2 and H3 headings.
• For overview, set the topic's context with a single paragraph.
• For body, explain the concept.
• For whatsnext, provide a bulleted list of topics (5 maximum) to learn more about the concept.

Annotations is a published example of a concept page.

Task

A task page shows how to do a single thing, typically by giving a short sequence of steps. Task pages have minimal explanation, but often provide links to conceptual topics that provide related background and knowledge.

To write a new task page, create a Markdown file in a subdirectory of the /content/en/docs/tasks directory, with the following characteristics:

The overview, steps, and discussion sections appear as comments in the task page. You can add the prerequisites and whatsnext sections to your page with the heading shortcode.

Within each section, write your content. Use the following guidelines:

• Use a minimum of H2 headings (with two leading # characters). The sections themselves are titled automatically by the template.
• For overview, use a paragraph to set context for the entire topic.
• For prerequisites, use bullet lists when possible. Start adding additional prerequisites below the include. The default prerequisites include a running Kubernetes cluster.
• For steps, use numbered lists.
• For discussion, use normal content to expand upon the information covered in steps.
• For whatsnext, give a bullet list of up to 5 topics the reader might be interested in reading next.

An example of a published task topic is Using an HTTP proxy to access the Kubernetes API.

Tutorial

A tutorial page shows how to accomplish a goal that is larger than a single task. Typically a tutorial page has several sections, each of which has a sequence of steps. For example, a tutorial might provide a walkthrough of a code sample that illustrates a certain feature of Kubernetes. Tutorials can include surface-level explanations, but should link to related concept topics for deep explanations.

To write a new tutorial page, create a Markdown file in a subdirectory of the /content/en/docs/tutorials directory, with the following characteristics:

The overview, objectives, and lessoncontent sections appear as comments in the tutorial page. You can add the prerequisites, cleanup, and whatsnext sections to your page with the heading shortcode.

Within each section, write your content. Use the following guidelines:

• Use a minimum of H2 headings (with two leading # characters). The sections themselves are titled automatically by the template.
• For overview, use a paragraph to set context for the entire topic.
• For prerequisites, use bullet lists when possible. Add additional prerequisites below the ones included by default.
• For objectives, use bullet lists.
• For lessoncontent, use a mix of numbered lists and narrative content as appropriate.
• For cleanup, use numbered lists to describe the steps to clean up the state of the cluster after finishing the task.
• For whatsnext, give a bullet list of up to 5 topics the reader might be interested in reading next.

An example of a published tutorial topic is Running a Stateless Application Using a Deployment.

Reference

A component tool reference page shows the description and flag options output for a Kubernetes component tool. Each page generates from scripts using the component tool commands.

A tool reference page has several possible sections:

Examples of published tool reference pages are:

• kubeadm init
• kube-apiserver
• kubectl

What's next

• Learn about the Style guide
• Learn about the Content guide
• Learn about content organization

6 - Content organization

This site uses Hugo. In Hugo, content organization is a core concept.

Page Lists

Page Order

The documentation side menu, the documentation page browser etc. are listed using Hugo's default sort order, which sorts by weight (from 1), date (newest first), and finally by the link title.

Given that, if you want to move a page or a section up, set a weight in the page's front matter:

title: My Page
weight: 10

Documentation Main Menu

The Documentation main menu is built from the sections below docs/ with the main_menu flag set in front matter of the _index.md section content file:

main_menu: true

Note that the link title is fetched from the page's linkTitle, so if you want it to be something different than the title, change it in the content file:

main_menu: true
title: Page Title
linkTitle: Title used in links

Documentation Side Menu

The documentation side-bar menu is built from the current section tree starting below docs/.

It will show all sections and their pages.

If you don't want to list a section or page, set the toc_hide flag to true in front matter:

toc_hide: true

When you navigate to a section that has content, the specific section or page (e.g. _index.md) is shown. Else, the first page inside that section is shown.

Documentation Browser

The page browser on the documentation home page is built using all the sections and pages that are directly below the docs section.

If you don't want to list a section or page, set the toc_hide flag to true in front matter:

toc_hide: true

The Main Menu

The site links in the top-right menu -- and also in the footer -- are built by page-lookups. This is to make sure that the page actually exists. So, if the case-studies section does not exist in a site (language), it will not be linked to.

Page Bundles

In addition to standalone content pages (Markdown files), Hugo supports Page Bundles.

One example is Custom Hugo Shortcodes. It is considered a leaf bundle. Everything below the directory, including the index.md, will be part of the bundle. This also includes page-relative links, images that can be processed etc.:

en/docs/home/contribute/includes
├── example1.md
├── example2.md
├── index.md
└── podtemplate.json

Another widely used example is the includes bundle. It sets headless: true in front matter, which means that it does not get its own URL. It is only used in other pages.

en/includes
├── default-storage-class-prereqs.md
├── index.md
├── partner-script.js
├── partner-style.css
├── task-tutorial-prereqs.md
├── user-guide-content-moved.md
└── user-guide-migration-notice.md

Some important notes to the files in the bundles:

• For translated bundles, any missing non-content files will be inherited from languages above. This avoids duplication.
• All the files in a bundle are what Hugo calls Resources and you can provide metadata per language, such as parameters and title, even if it does not supports front matter (YAML files etc.). See Page Resources Metadata.
• The value you get from .RelPermalink of a Resource is page-relative. See Permalinks.

Styles

The SASS source of the stylesheets for this site is stored in assets/sass and is automatically built by Hugo.

What's next

• Learn about custom Hugo shortcodes
• Learn about the Style guide
• Learn about the Content guide

7 - Custom Hugo Shortcodes

This page explains the custom Hugo shortcodes that can be used in Kubernetes Markdown documentation.

Read more about shortcodes in the Hugo documentation.

Feature state

In a Markdown page (.md file) on this site, you can add a shortcode to display version and state of the documented feature.

Feature state demo

Below is a demo of the feature state snippet, which displays the feature as stable in the latest Kubernetes version.

{{< feature-state state="stable" >}}

Renders to:

The valid values for state are:

• alpha
• beta
• deprecated
• stable

Feature state code

The displayed Kubernetes version defaults to that of the page or the site. You can change the feature state version by passing the for_k8s_version shortcode parameter. For example:

{{< feature-state for_k8s_version="v1.10" state="beta" >}}

Renders to:

Feature state retrieval from description file

To dynamically determine the state of the feature, make use of the feature_gate_name shortcode parameter. The feature state details will be extracted from the corresponding feature gate description file located in content/en/docs/reference/command-line-tools-reference/feature-gates/. For example:

{{< feature-state feature_gate_name="NodeSwap" >}}

Renders to:

Feature gate description

In a Markdown page (.md file) on this site, you can add a shortcode to display the description for a shortcode.

Feature gate description demo

Below is a demo of the feature state snippet, which displays the feature as stable in the latest Kubernetes version.

{{< feature-gate-description name="DryRun" >}}

Renders to:

DryRun: Enable server-side dry run requests so that validation, merging, and mutation can be tested without committing.

Glossary

There are two glossary shortcodes: glossary_tooltip and glossary_definition.

You can reference glossary terms with an inclusion that automatically updates and replaces content with the relevant links from our glossary. When the glossary term is moused-over, the glossary entry displays a tooltip. The glossary term also displays as a link.

As well as inclusions with tooltips, you can reuse the definitions from the glossary in page content.

The raw data for glossary terms is stored at the glossary directory, with a content file for each glossary term.

Glossary demo

For example, the following include within the Markdown renders to cluster with a tooltip:

{{< glossary_tooltip text="cluster" term_id="cluster" >}}

Here's a short glossary definition:

{{< glossary_definition prepend="A cluster is" term_id="cluster" length="short" >}}

which renders as:

A cluster is a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.

You can also include a full definition:

{{< glossary_definition term_id="cluster" length="all" >}}

which renders as:

A set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.

The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.

Links to API Reference

You can link to a page of the Kubernetes API reference using the api-reference shortcode, for example to the Pod reference:

{{< api-reference page="workload-resources/pod-v1" >}}

The content of the page parameter is the suffix of the URL of the API reference page.

You can link to a specific place into a page by specifying an anchor parameter, for example to the PodSpec reference or the environment-variables section of the page:

{{< api-reference page="workload-resources/pod-v1" anchor="PodSpec" >}}
{{< api-reference page="workload-resources/pod-v1" anchor="environment-variables" >}}

You can change the text of the link by specifying a text parameter, for example by linking to the Environment Variables section of the page:

{{< api-reference page="workload-resources/pod-v1" anchor="environment-variables" text="Environment Variable" >}}

Table captions

You can make tables more accessible to screen readers by adding a table caption. To add a caption to a table, enclose the table with a table shortcode and specify the caption with the caption parameter.

Here's an example:

{{< table caption="Configuration parameters" >}}
Parameter | Description | Default
:---------|:------------|:-------
`timeout` | The timeout for requests | `30s`
`logLevel` | The log level for log output | `INFO`
{{< /table >}}

The rendered table looks like this:

If you inspect the HTML for the table, you should see this element immediately after the opening <table> element:

<caption style="display: none;">Configuration parameters</caption>

Tabs

In a markdown page (.md file) on this site, you can add a tab set to display multiple flavors of a given solution.

The tabs shortcode takes these parameters:

• name: The name as shown on the tab.
• codelang: If you provide inner content to the tab shortcode, you can tell Hugo what code language to use for highlighting.
• include: The file to include in the tab. If the tab lives in a Hugo leaf bundle, the file -- which can be any MIME type supported by Hugo -- is looked up in the bundle itself. If not, the content page that needs to be included is looked up relative to the current page. Note that with the include, you do not have any shortcode inner content and must use the self-closing syntax. For example, {{< tab name="Content File #1" include="example1" />}}. The language needs to be specified under codelang or the language is taken based on the file name. Non-content files are code-highlighted by default.
• If your inner content is markdown, you must use the %-delimiter to surround the tab. For example, {{% tab name="Tab 1" %}}This is **markdown**{{% /tab %}}
• You can combine the variations mentioned above inside a tab set.

Below is a demo of the tabs shortcode.

Tabs demo: Code highlighting

{{< tabs name="tab_with_code" >}}
{{< tab name="Tab 1" codelang="bash" >}}
echo "This is tab 1."
{{< /tab >}}
{{< tab name="Tab 2" codelang="go" >}}
println "This is tab 2."
{{< /tab >}}
{{< /tabs >}}

Renders to:

• Tab 1
• Tab 2

echo "This is tab 1."

println "This is tab 2."

Tabs demo: Inline Markdown and HTML

{{< tabs name="tab_with_md" >}}
{{% tab name="Markdown" %}}
This is **some markdown.**
{{< note >}}
It can even contain shortcodes.
{{< /note >}}
{{% /tab %}}
{{< tab name="HTML" >}}
<div>
	<h3>Plain HTML</h3>
	<p>This is some <i>plain</i> HTML.</p>
</div>
{{< /tab >}}
{{< /tabs >}}

Renders to:

• Markdown
• HTML

Tabs demo: File include

{{< tabs name="tab_with_file_include" >}}
{{< tab name="Content File #1" include="example1" />}}
{{< tab name="Content File #2" include="example2" />}}
{{< tab name="JSON File" include="podtemplate" />}}
{{< /tabs >}}

Renders to:

• Content File #1
• Content File #2
• JSON File

  {
    "apiVersion": "v1",
    "kind": "PodTemplate",
    "metadata": {
      "name": "nginx"
    },
    "template": {
      "metadata": {
        "labels": {
          "name": "nginx"
        },
        "generateName": "nginx-"
      },
      "spec": {
         "containers": [{
           "name": "nginx",
           "image": "dockerfile/nginx",
           "ports": [{"containerPort": 80}]
         }]
      }
    }
  }

Source code files

You can use the {{% code_sample %}} shortcode to embed the contents of file in a code block to allow users to download or copy its content to their clipboard. This shortcode is used when the contents of the sample file is generic and reusable, and you want the users to try it out themselves.

This shortcode takes in two named parameters: language and file. The mandatory parameter file is used to specify the path to the file being displayed. The optional parameter language is used to specify the programming language of the file. If the language parameter is not provided, the shortcode will attempt to guess the language based on the file extension.

For example:

{{% code_sample language="yaml" file="application/deployment-scale.yaml" %}}

The output is:

application/deployment-scale.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 4 # Update the replicas from 2 to 4
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.16.1
        ports:
        - containerPort: 80

When adding a new sample file, such as a YAML file, create the file in one of the <LANG>/examples/ subdirectories where <LANG> is the language for the page. In the markdown of your page, use the code shortcode:

{{% code_sample file="<RELATIVE-PATH>/example-yaml>" %}}

where <RELATIVE-PATH> is the path to the sample file to include, relative to the examples directory. The following shortcode references a YAML file located at /content/en/examples/configmap/configmaps.yaml.

{{% code_sample file="configmap/configmaps.yaml" %}}

The legacy {{% codenew %}} shortcode is being replaced by {{% code_sample %}}. Use {{% code_sample %}} (not {{% codenew %}} or {{% code %}}) in new documentation.

Third party content marker

Running Kubernetes requires third-party software. For example: you usually need to add a DNS server to your cluster so that name resolution works.

When we link to third-party software, or otherwise mention it, we follow the content guide and we also mark those third party items.

Using these shortcodes adds a disclaimer to any documentation page that uses them.

Lists

For a list of several third-party items, add:

{{% thirdparty-content %}}

just below the heading for the section that includes all items.

Items

If you have a list where most of the items refer to in-project software (for example: Kubernetes itself, and the separate Descheduler component), then there is a different form to use.

Add the shortcode:

{{% thirdparty-content single="true" %}}

before the item, or just below the heading for the specific item.

Version strings

To generate a version string for inclusion in the documentation, you can choose from several version shortcodes. Each version shortcode displays a version string derived from the value of a version parameter found in the site configuration file, hugo.toml. The two most commonly used version parameters are latest and version.

{{< param "version" >}}

The {{< param "version" >}} shortcode generates the value of the current version of the Kubernetes documentation from the version site parameter. The param shortcode accepts the name of one site parameter, in this case: version.

Renders to:

{{< latest-version >}}

The {{< latest-version >}} shortcode returns the value of the latest site parameter. The latest site parameter is updated when a new version of the documentation is released. This parameter does not always match the value of version in a documentation set.

Renders to:

{{< latest-semver >}}

The {{< latest-semver >}} shortcode generates the value of latest without the "v" prefix.

Renders to:

{{< version-check >}}

The {{< version-check >}} shortcode checks if the min-kubernetes-server-version page parameter is present and then uses this value to compare to version.

Renders to:

{{< latest-release-notes >}}

The {{< latest-release-notes >}} shortcode generates a version string from latest and removes the "v" prefix. The shortcode prints a new URL for the release note CHANGELOG page with the modified version string.

Renders to:

What's next

• Learn about Hugo.
• Learn about writing a new topic.
• Learn about page content types.
• Learn about opening a pull request.
• Learn about advanced contributing.