DevopsPilot

Helm Interview Questions

What is the folder structure of Helm chart?

|Chart.yaml |A YAML file containing information about the chart|
|LICENSE |OPTIONAL: A plain text file containing the license for the chart|
|README.md |OPTIONAL: A human-readable README file|
|values.yaml |The default configuration values for this chart|
|values.schema.json|OPTIONAL: A JSON Schema for imposing a structure on the values.yaml file|
|charts/ |A directory containing any charts upon which this chart depends.|
|crds/ |Custom Resource Definitions|
|templates/ |A directory of templates that, when combined with values, will generate valid Kubernetes manifest files.|
|templates/NOTES.txt|OPTIONAL: A plain text file containing short usage notes|

Official Documentation

How you can mark the Helm chart as Deprecated ?

deprecated field in Chart.yaml can be used to mark a chart as deprecated.

Official Documentation

How you can add the helm chart repository to the helm client ?

helm repo add devopspilot https://devopspilot.com/helm/charts/
helm repo update

devopspilot –> alias repo name to point to the Helm chart repository.

https://devopspilot.com/helm/charts/ –> Helm chart repository url.

How you can install the helm chart to specific namespace ?

By passing cli flag -n or --namespace

helm install mysql devopspilot/mysql -n database

You have installed Helm chart, somebody from the team updated pod manifest manually, after which when you update the same Release what will happen?

Can we have same Release names in different namespaces?

Yes we can have same release name in two different namespaces.

Eg: Lets install mysql chart with same Release name mysql in two different namespaces database1 and database2

helm install mysql devopspilot/mysql -n database1
Output:
NAME: mysql
LAST DEPLOYED: Tue Jul 20 20:58:55 2021
NAMESPACE: database1
STATUS: deployed
REVISION: 1
TEST SUITE: None
helm install mysql devopspilot/mysql -n database2
Output:
NAME: mysql
LAST DEPLOYED: Tue Jul 20 21:01:21 2021
NAMESPACE: database2
STATUS: deployed
REVISION: 1
TEST SUITE: None

You are installing mysql chart in database namespace. But you haven’t created the database namespace before installing, what will happen ?

Helm install will fail with an error. Namespace should be created before installing chart.

Eg: Here we are installing mysql chart in database namespace. But database namespace is not created

helm install mysql devopspilot/mysql -n database 
Output:
Error: create: failed to create: namespaces "database" not found

Is it possible to create namespace using helm commands while installing the chart ?

Yes, its possible to create the namespace using helm install command by passing argument --create-namespace

helm install mysql devopspilot/mysql -n database --create-namespace

What functions have you used in helm charts? Can you list down some functions ?

default, lookup, eq, ne, lt, gt, and, or

Official Documentation

How will you manage environment specific values.yaml?

Maintain one values.yaml for each environment.

What is the use of _helpers.tpl?

It is used to define some templates or functions and then it can be referred in Kubernetes manifest files in templates folder.

Did you work on any flow controls, if yes where did you use?

if/else for creating conditional blocks

with to specify a scope

range which provides a “for each”-style loop

Official Documentation

You have installed the chart which has CRDs. Now you are updating the same Release with updated chart, what will happen to the CRDs ?

CRDs are never reinstalled. If Helm determines that the CRDs in the crds/ directory are already present (regardless of version), Helm will not attempt to install or upgrade.

CRDs are never installed on upgrade or rollback. Helm will only create CRDs on installation operations.

You have installed the chart which has CRD. Now you have uninstalled the chart, what will happen to the created CRDs ?

The created CRDs will not be deleted automatically during helm uninstall. We have to explicitly delete the CRDs.

What is the default timeout wile installing each kubernetes object using Helm ?

The default duration time to wait for any individual Kubernetes operation (like Jobs for hooks) (default 5m0s).

We are override this timeout limit by passing the cli flag --timeout to helm install/update command.

helm install mysql devopspilot/mysql -n database --timeout 10m

You are going to install the chart which has some hooks. While installing the chart you want to skip those hooks. Is it possible ?

Yes its possible to skip the helm hooks during installation by passing the cli flag --no-hooks

helm install easyclaim-backend devopspilot/easyclaim-backend --no-hooks

While installing the chart, you have passed two values.yaml file for the helm install command, which has the highest priority ?

The rightmost values.yaml file passed as cli flag to helm install command has highest priority.

helm install mysql devopspilot/mysql -f values.yaml -f values-dev.yaml

While installing the chart, you have specified both values.yaml and --set cli-flag for the helm install command, what will happen now ?

If both are passed, --set values are merged into passed values.yaml and then the values.yaml file is passed to helm install command.

helm install mysql devopspilot/mysql --set deploymentType=statefulset -f values.yaml

How will you define dependency charts ?

We can define dependency chart in parent Chart.yaml under dependencies field.

apiVersion: v2
name: easyclaim
version: 1.0.0
description: Helm chart for deploying Easyclaim application
appVersion: 1.0.0

dependencies:
  - name: easyclaim-frontend
    version: 1.0.0
    repository: https://devopspilot.com/helm/charts
  - name: easyclaim-backend
    version: 1.0.0
    repository: https://devopspilot.com/helm/charts
  - name: mysql
    version: 1.0.0
    repository: https://devopspilot.com/helm/charts

Official Documentation

You have a chart locally and defined couple of dependency charts in Chart.yaml file. Whether you can directly install the chart or you have to run any other commands before running helm install command ?

We have to run helm dependency update command so that the dependency charts will be downloaded and stored in charts directory and then we can install the chart.

helm dependency update
Output:
Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "devopspilot" chart repository
Update Complete. ⎈Happy Helming!⎈
Saving 3 charts
Downloading easyclaim-frontend from repo https://devopspilot.com/helm/charts
Downloading easyclaim-backend from repo https://devopspilot.com/helm/charts
Downloading mysql from repo https://devopspilot.com/helm/charts
Deleting outdated charts

You have defined couple of dependency charts. In which order the charts will be installed ?

First all the charts will be merged together and then the manifest files will be deployed in the right order.

Helm has the intelligence to install all the manifests in right order. We no need to handle it manually.

How will you push the helm chart to Chart museum ?

How will you push the helm chart to Jfrog artifactory helm repository ?

Is it possible to skip the installation of crds while installing the chart ?

Yes, its possible to skip the installation of CRDs while installing the chart by passing argument --skip-crds

helm install mysql devopspilot/mysql --skip-crds

Is it possible to install the chart using helm upgrade ? If possible how to do it

Yes, its possible to install the chart using the helm upgrade by passing argument --install

If the chart is already installed it will upgrade or it will install the chart

helm upgrade --install mysql devopspilot/mysql

During the helm upgrade, if the helm install is failed, will it rollback to previous version ?

By default no, by passing argument –atomic, it can rollback automatically to previous version

helm upgrade --atomic --cleanup-on-fail mysql devopspilot/mysql