Application Environments Are Complex

Docker can help simplify application deployment with "containers".
Docker-compose can help manage interaction between several "containers".
Kubernetes can help simplify deploying containers into pods, introduce communication layers through services, introduce secure secret storage through secrets, abstract away data-storage solutions through persistent volumes and persistent volume claims... etc.
This is complex - especially in application suites where many parts are involved. Even a trivial traditional "full-stack" app, with a db, an api layer, and a frontend layer, can have all-of-the-above parts involved.

Application Environments Are Complex

Yaml Files Are Everywhere

app.deployment.yaml
nginx.deployment.yaml
secret.yaml
pv.yaml
pvc.yaml
app-service.yaml

Managing these can require touching several of these yaml files every time something across the deployment needs updating.

Heml To The Rescue

K8s doesn't really "care" about the details of the app.
K8s creates objects.
K8s manages object lifecycles.
Helm looks at details of the parts involved across a k8s system, and "cares" more about the inter-connected details.
Helm uses a values.yaml file.
Details can be configured in the values.yaml file.

# get it going
helm install app ...

# update one or part of the suite of K8s objects
helm upgrade app ...

# rollback the suite of K8s objects
helm rollback app ...

# remove the suite of K8s objects with 1 command
helm uninstall app ...

Get It Going

Install Helm. Check the docs here.
Get K8s and kubectl installed on the host machine - here, my laptop.

# install with snap
sudo snap install helm --classic
# instsall with apt
# add key + sources list prior
curl https://baltocdn.com/helm/signing.asc | sudo apt-key add -
sudo apt-get install apt-transport-https --yes
echo "deb https://](https://baltocdn.com/helm/stable/debian/ all main" | sudo tee /etc/apt/sources.list.d/helm-stable-debian.list
sudo apt-get install helm

Another set of directions from the debia/ubuntu section of the docs:

curl https://baltocdn.com/helm/signing.asc | gpg --dearmor | sudo tee /usr/share/keyrings/helm.gpg > /dev/null
sudo apt-get install apt-transport-https --yes
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/helm.gpg] https://baltocdn.com/helm/stable/debian/ all main" | sudo tee /etc/apt/sources.list.d/helm-stable-debian.list
sudo apt-get update
sudo apt-get install helm

Helm Charts

Consider Kubernetes across environments: qa might require different details across k8s objects than production: container image versions, pv storage disk allocation limits, object passwords, etc.
These Values can be abstracted out of K8s object config files, entirely, and referenced with key: {{ .Values.value-key-here }}. Values.yaml will then contain values to be used across the kubernetes objects. Templates for all of the the kubernetes objects can also be created.
The templates and values are known as a helm chart.
Again:

Templates
values.yaml
Chart.yaml: this has info about the chart, itself - some metadata on top of metadata on top of...

Use the Helm Repo

Use the web interface to search.

Alternative to the web guis, use the cli:

# helm search hub <val here>
helm search hub wordpress

Artifacthub seems to be the growing place to store helm charts - something like the npm repo of k8s configurations.

Consider alternative helm repositories

There are a bunch of helm chart repos, like one in bitnami.

# point to a different helm "hub", or chart repo - called bitnami
helm repo add bitnami https://charts.bitnami.com/bitnami

# use it
helm search repo wordpress

# see all repos available to reference on the host machine
helm repo list

Install a chart

The "release name", below, is the helm chart instance friendly name we assign to the applied chart.

# helm install [release-name] [chart-name]
helm install release-1 bitnami/wordpress
helm install release-2 bitnami/wordpress
helm install release-3 bitnami/wordpress

Helm Commands

# show installed packages
helm list

# remove a package
helm uninstall package-here

# untar extracts the contents from a tar file that is downloaded.  
helm pull --untar bitnami/wordpress

Tags:

Kubernetes