Cheat Sheet for Helm v3

helm-cheat-sheet.md

Helm Cheat Sheet

For Helm 3.

Concepts

Helm is a Package Manager for Kubernetes.

Just like:

YUM is a Package Manager for Fedora and Redhat Linux.

APT and Snap are Package Managers for Ubuntu Linux.

Chocolatey is a Package Manager for Windows.

A Package Manager knows how to install, configure, upgrade, verify and uninstall packages and their dependencies.

Comparison of Package Managers

Package Manager	Package Type	File Type
Helm	chart (lowercase by convention)	.tgz - gzip compressed, tar archive
YUM	RPM	.rpm
APT	deb	.deb

A Helm chart is a software package for Kubernetes.

Chart structure

my-app-chart/
├── Chart.yaml
├── charts                  
├── templates
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── serviceaccount.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

File/Directory	Description
my-app-chart/	chart name. Must be lowercase letters and numbers and dashes.
├── Chart.yaml	contains chart metadata (versions, dependencies, etc).
├── charts	directory containing sub-charts.
├── templates	directory containing golang templates to be pre-processed before posting to the kubernetes API.
│   ├── NOTES.txt	welcome banner and getting started messages shown on successful install or upgrade.
│   ├── _helpers.tpl	files prefixed with an _ are pre-processed templates, but not sent to the kubernetes API server.
│   ├── deployment.yaml	contains templated kubernetes resource definition.
│   └── tests	directory containing chart tests to be run by helm test on a release.
│   └── test-connection.yaml
└── values.yaml	contains key-value pairs to be rendered in templates during Helm pre-processing stage.

A Helm Release is a named, deployed instance of the Chart.

A Revision is a snapshot of a Release in history.

Element of a Release	Description
hooks	controls the order of templates applied at different stages of the Release lifecycle i.e. pre-install, post-upgrade, pre-rollback. Manifest annotations.
manifest	templated kubernetes YAML manifests.
notes	welcome banner and getting started messages shown on successful install or upgrade.
values	values used to generate the release.

A Repository (or repo) is a place to store and search for versioned charts. Its an indexed filesystem of .tgz archives.

Helm Hub (now artifacthub.io) is a portal for finding Helm Charts across community repositories.

A Plugin is a Helm client extension providing extra sub-commands or features (e.g. helm diff).

About the Project

Conventions

Semantic Versioning

Helm uses Semantic Versioning for Charts and Helm itself.

The latest version of Helm (at the time of writing) is:

3.4.1

major.minor.patch+build.metadata

Examples:

• Helm v3.4.1 API is not backwards compatible with Helm v2.17.0. 3 is one major version up from 2.

However, most Helm 2 Charts should work with Helm 3 (CRDs excepted).

• Helm v3.4.0 is four minor versions up from v3.0.3. Those minor changes are backwards compatible.
• Helm v3.0.3 has 3 bug fixes on v3.0.0.
• my-chart 1.17.2+20201008195643.ffe0fa8.11 has dot-delimited build metadata:
  • 20201008195643 timestamp of the build.
  • ffe0fa8 git commit short hash.
  • 11 build number.

When SemVer versions are stored in Kubernetes labels, we conventionally alter the + character to an _ character, as labels do not allow the + sign as a value.

Chart Naming

The directory that contains a chart MUST have the same name as the chart. Chart name must be lowercase letters, numbers, and/or dashes e.g. helm-cheat-sheet

Grammar

helm is the command line tool.

Helm is the project.

The term chart does not need to be capitalized, as it is not a proper noun.

Use Cases

Complementary Operations

[flags] and [global flags] options omitted for brevity

Operation		Complementary Operation
Install	helm install [RELEASE_NAME] [CHART]	Uninstall	helm uninstall RELEASE_NAME [...]
Upgrade	helm upgrade [RELEASE] [CHART]	Rollback	helm rollback <RELEASE> [REVISION]
Sign	helm package [CHART_PATH] [...] --sign	Verify	helm verify PATH

Chart Development

Operation	Description
Create	create a new chart with the given name	helm create NAME
Lint	examine a chart for possible issues	helm lint PATH
Package	package a chart directory into a chart archive	helm package [CHART_PATH] [...]

Quick Start - Get Interactive with helm !

Assumes bash shell and that the bash-completion package is installed on a Linux distro.

Set up helm auto-completion on the command line. Use double <TAB> to auto-complete commands.

$ . /usr/share/bash-completion/bash_completion
$ source <(helm completion bash)

Example:

bash-5.0# helm <TAB><TAB>
completion  dependency  env         helm-git    install     list        plugin      repo        s3          secrets     status      test        upgrade     version     
create      diff        get         history     lint        package     pull        rollback    search      show        template    uninstall   verify 

Include dry run, fail safe, backups