Helm seems to be like a container deployment like what puppet/ansible is for application deployment/installation.

tar up all the yaml files used to deploy the whole solution. Includeing deployments, services, ingress etc.

• Where are the charts stored locally
• how does the helm thing map to apt
• is it like terraform, but for k8s container instead of VMs?

• Helm home page
• Blo20 - 'Learning HELM' by Andrew Block and Austin Dewey, 2020 Packt Publishing
• Nan20 -

• Chart - an archived set of Kubernetes resource manifests that make up a distributed applicationLFS258.
• ConfigMap - TODO
• CR - Custom Resource[Blo20,p115]
• CRD - Custom Resource Definition[Blo20,p115]

• Helm uses the kubeconfig(Nan20, 4.6)
  • e.g. /home/ubuntu/.kube/config
  • so whatever kubectl is poiting to is what helm is using as well(Nan20, 4.6).

• helm create first-chart
• helm dependency
  • helm dependency build - Rebuilds the charts/directory based on the Chart.lock file[Blo20,p122]
    • TODO improve description
    • If a Chart.lock file is not found, this command will mirror the behavior of the helm dependency update command
  • helm dependency list - List the dependencies for the given chart[Blo20,p122]
  • helm dependency update - Updates the charts/directory based on the content of Chart.yaml and generate a Chart.lock file[Blo20,p122]
    • To download dependencies for the first time, you can run the helm dependency update command, which downloads each dependency into the charts/ directory of the given Helm chart[Blo20,p122]
      • helm dependency update $CHART_PATH
    • The helm dependency update command downloads dependencies from repositories in the form of GZip archives with the .tgz file extension[Blo20,p122].
    • This command also generates a file called Chart.lock[Blo20,p122].
      • The Chart.lock file is similar to the Chart.yaml file[Blo20,p122].
      • However, while the Chart.yaml file contains the desired state of the chart dependencies,
      • the Chart.lock file defines the actual state of the dependencies that were applied[Blo20,p122].
• helm lint .
• helm template first-chart .
  • show how changes you have made?
• helm install first-chart .
  • helm install wordpress bitnami/wordpress --values=wordpress-values.yaml --namespace chapter3 --version 8.1.0
• helm upgrade first-chart .
• helm history first-chart
• helm repo add
  • helm repo add bitnami https://charts.bitnami.com/bitnami
  • helm search repo bitnami
  • helm search repo wordpress
  • helm search repo wordpress --versions
• helm rollback first-chart
  • helm rollback first-chart 2
• helm search hub - search the helm hub for charts(Blo20, 56)
  • helm search hub wordpress --output yaml
  • helm search hub wordpress  --max-col-width=0
• helm search repo - search the local repo for charts(Blo20, 56)
• helm show
  • helm show values bitnami/wordpress --version 13.2.1
  • helm show readme bitnami/wordpress --version 8.1.0

1. helm search hub wordpress --list-repo-url | grep bitnami
2. put the URL into your web browser: https://artifacthub.io/packages/helm/bitnami/wordpress
3. Go to the TL;DR; for the installation step
4. helm repo add bitnami https://charts.bitnami.com/bitnami
5. helm install my-release bitnami/wordpress
6. mk service list
7. or mk service my-release-wordpress which will open the browser to the service
8. helm delete my-release

The primary purpose of a Helm chart is to create and manage the Kubernetes resources that make up an application[Bol20,p?].

• .helmignore
• Chart.lock
• Chart.yaml - contains some metadata about the Chart, like its name, version, keywords, and so on[lfs258]
• templates - contains the resource manifests that make up the application[lfs258]
• values*.yaml - contains keys and values that are used to generate the release in your cluster[lfs258].
  • These values are replaced in the resource manifests using the Go templating syntax[lfs258]

• string:
• integer:
• boolean:
  • true
  • false
  • yes
  • no
  • on
  • off
  • y
  • n
  • Y
  • N
• list

Relevant fields[Bo20,p118]:

• apiVersion - chart API version
  • v2
• appVersion - Application version
  • TODO where is this used?
• name - name of the helm chart
• version - version of the helm chart
  • TODO where is this used?

Other metadata

• dependencies -
• description -
• home -
• icon - an icon in SVG/PNG (TODO is this the content or a reference). Displayed in the chart's page on Helm hub[Bo20,p119].
• type - application/library[Blo20,p115]

• This schema can be used to validate the provided values during an installation or an upgrade[Blo20,p105].
• This file is a good way of ensuring users only provide the values that are supported as parameters in the chart's templates[Blo20,p105].

TODO how to use this?

[Blo20,p120]

TODO could you use this, to install the whole system (all applications in the system)

dependencies:
- condition: memcached.enabled
  name: memcached
  repository: https://charts.bitnami.com/bitnami
  version: 6.x.x
- condition: mariadb.enabled
  name: mariadb
  repository: https://charts.bitnami.com/bitnami
  version: 11.x.x

• name - [Required]Name of the dependency chart[Blo20,p121]
• repository - [Required] [Blo20,p121]
• version - [Required] version of the depency chart to include[Blo20,p121]
  • 7.x.x, which instructs Helm to download the latest version of the chart that matches the wildcard[Blo20,p121].
• alias - [optional] alternative name to give a dependency[Blo20,p121]
• condition - [optional] A boolean value that determines whether the dependency should be included or not[Blo20,p121]
• import-values - [optional] [Blo20,p121]
• tags - [optional] [Blo20,p121]

[Blo20,p115]

• Application charts are used to deploy full applications to Kubernetes[Blo20,p115].
• Library charts are used to provide named templates that may be used across multiple different charts[Blo20,p115].
  • If set to library, the chart provides functions to other charts through the form of helper templates[Blo20,p119].

[Blo20,p115]

• CRDs that must be presented before templates are installed[Blo20,p115]

• CRs can be created using Helm templates such as native Kubernetes resources, but there must first be a Custom Resource Definition (CRD) that defines the CR[Blo20,p115].

  • If the CRD is not present before the CR is created, the installation will fail[Blo20,p115].

• creating CRDs requires escalated privileges, requiring the user to be a cluster administrator[Blo20,p116].

Helm templates are the 'brains' of your Helm chart and are used to generate Kubernetes resources[Bol20,p116].

It seems that '{{ }}' are referred to as Go templates(lrn103)

• Go templates beginning with .Values will reference values defined in a values.yaml

See also

• .Capabilities.APIVersions - return a list of the API versions available in the k8s cluster.[Blo20,p104]

  • TODO what is this used for?

• .Chart - refer to fiels in the Chart.yaml file[Blo20,p104].

• .Files - file operations?

  • .Files.AsConfig - Returns file bodies as a YAML map to create ConfigMap data from files in a chart directory[Blo20,p104]
  • .Files.AsSecrets - Returns a file as a Base64-encoded string to create secret data from files a chart directory[Blo20,p104]
    • TODO figure out what this means.
  • .Files.Get - get a file in a chart directory.

• .Release - provided by helm/read from helm

  • e.g. .Release.Namespace The namespace to operate on.

• .Template.Name - Returns the relative file path to the template that this object uses[Blo20,p104]

• .Values - refer to values in the values.yaml files

• The dot (.) prefixed to each object represents the object scope[Blo20,p104].

  • A dot followed by an object name limits the scope to that object.
    • For example,
      • the .Values scope only makes a chart's values visible;
      • the .Release scope only makes fields under the Release object visible;
      • the . scope represents global scope, making all of these objects visible, plus the common objects defined in the preceding table

[Blo20,p108]

{{ $myvar := 'Hello World!' }}

data:
  greeting.txt: |
    {{ $myvar }}

[Blo20,p110]

[Blo20,p113]

• if/else - [Blo20,p106]
• with - [Blo20,p106]
• range - [Blo20,p106]

[Blo20,p112]

• and
• or
• not
• eq (short for equal)
• ne (short for not equal)
• lt (short for less than)
• le (short for less than or equal to)
• gt (short for greater than)
• ge (short for greater than or equal to)

[Blo20,p108]

spec:
  ports:
{{- range .Values.servicePorts }}
  - name: {{ - name }}
  port: {{ .port }}
{{- end }}

The with action allows a developer to modify the scope of these values and reference them with a shortened syntax[Blo20,p107]:

{{- with .Values.application.resources.limits }}
cpu: {{ .cpu }}
memory: {{ .memory }}
{{- end }}

It seems like this contains the .yaml files you would normally use for kubernetes, like configmap.yaml, service.yaml etc.

These files are templating files, which can contain references to variables '{{ .Release.Name }}', these templates will be rendered into full kubernetes yaml files, during install and upgrade.

This file declares all of a chart's default values, which are referenced by Go templates and processed by Helm to dynamically generate Kubernetes resources(lrn).

Installing helm

1. curl https://baltocdn.com/helm/signing.asc | sudo apt-key add -
2. sudo apt-get install apt-transport-https --yes
3. echo "deb https://baltocdn.com/helm/stable/debian/ all main" | sudo tee /etc/apt/sources.list.d/helm-stable-debian.list
4. sudo apt-get update
5. sudo apt-get install helm

• helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx(Nan20, 4.6)
• helm repo update
• helm install ingress-nginx ingress-nginx/ingress-nginx
  • helm install <release_name> <chart_name>

1. mkdir helm-course
2. cd helm-course
3. helm create first-chart
4. find first-chart

• values.yaml - various config values? Used in the interpretation of the various other files like the files in 'templates/'
• templates/ - used for generating kubernetes manifests
  • _helpers.tpl
  • deployment.yaml
  • serviceaccount.yaml
  • hpa.yaml
  • ingress.yaml
  • NOTES.txt - displayed in the terminal when someone downloads this chart.
  • service.yaml
  • tests/
    • test-connection.yaml
• Chart.yaml
• charts/ - store sub-charts that are dependencies of the top level chart
• .helmignore

Helm plugins

• helm secrets
• helm unittest
• helm monitor

helm plugin CMD

Chart.yaml missing[Bol20,p116]