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.

Note: Kubernetes documentation uses Goldmark Markdown Renderer with some adjustments along with a few Hugo Shortcodes to support glossary entries, tabs, and representing feature state.

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.

Note: The website supports syntax highlighting for code samples, but specifying a language is optional. Syntax highlighting in the code block should conform to the contrast guidelines.

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, please 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, please 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:

Note: You can still use Markdown inside these callouts.

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.

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:

Caution: The callout style only applies to the line directly above the tag.

Warning

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

For example:

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

The output is:

Warning: Beware.

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.