Helm is a package manager for Kubernetes. It works with packages of pre-configured Kubernetes resources, called Helm charts.
With Helm you can:
- find, deploy and manage software in Kubernetes using a growing catalog of Helm charts
- create and share your own Helm charts
Before you begin
This tutorial assumes that you already have a working OVHcloud Managed Kubernetes cluster, and some basic knowledge of how to operate it. If you want to know more on those topics, please look at the OVHcloud Managed Kubernetes Service Quickstart.
We are assuming that you have the KUBECONFIG environment variable pointing to your KubeCtl configuration file, as described in the Quickstarter. If that’s not the case, you can use the --kubeconfig [LOCATION_OF_CONFIG_FILE] option in both kubectl and helm calls.
Helm concepts
Helm is built around three big concepts: charts, repositories and releases.
A chart is a Helm package. Inside the chart you have all the resource definitions necessary to run an application, tool, or service inside of a Kubernetes cluster. It’s the Helm equivalent of a Debian pkg for linux, a Maven file for Java or a package.json for Node JS.
Charts are stored in repositories, where they can be shared. Repositories are the Helm equivalent of the NPM registry for Node JS or Maven Central for Java.
When a chart is installed in a Kubernetes cluster, the running instance is called a release. Multiple releases of a single chart can be installed at the same time in a cluster (think for example several instance of the Wordpress chart for several different blogs instances running in the cluster).
Installing Helm
Warning: This guide supposes you’re using Helm 3, the latest major version of Helm. The precedent version, Helm 2, is in maintenance mode, and considered deprecated. If you want to use Helm 2, please refer to the official documentation
Every release of Helm provides binary releases for a variety of OSes. These binary versions can be manually downloaded and installed.
The simplest way to install Helm is grabbing the binary release for your platform on the official release page. You then just need to unpack the client helm binary and add it to your PATH.
To use alternative installation procedures, like package managers (Homebrew, Snap etc.), please refer to the official installation doc.
Initialize a Helm Chart Repository
Warning: As with Helm 2, the official Helm stable repository is currently deprecated. The Helm community is currently transitioning to a hub model, with a Helm Hub, where charts can be searched using helm search hub <keyword> As most charts from the Helm stable repository have been transferred to the Bitnami repository we are using it in the tutorial.
Once you have Helm ready, you can add a chart repository. The easiest way to begin with Helm is to add the Bitnami repository:
# helm repo add bitnami https://charts.bitnami.com/bitnami
Once the repository added, run helm repo updateto make sure we get the latest list of charts
# helm repo add bitnami https://charts.bitnami.com/bitnami "bitnami" has been added to your repositories # helm repo update Hang tight while we grab the latest from your chart repositories... ...Successfully got an update from the "bitnami" chart repository Update Complete. ⎈ Happy Helming!⎈
Installing an example chart
Let’s validate your Helm installation by installing an example chart, the official Redis one, with no persistence:
# helm install test-redis bitnami/redis --set master.persistence.enabled=false
This will install the required elements and initialize the services. And at the end, it will give you the connection parameters for your new Redis database:
# helm install test-redis bitnami/redis --set master.persistence.enabled=false
NAME: test-redis
LAST DEPLOYED: Tue Apr 14 15:13:14 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
** Please be patient while the chart is being deployed **
Redis can be accessed via port 6379 on the following DNS names from within your cluster:
test-redis-master.default.svc.cluster.local for read/write operations
test-redis-slave.default.svc.cluster.local for read-only operations
To get your password run:
export REDIS_PASSWORD=$(kubectl get secret --namespace default test-redis -o jsonpath="{.data.redis-password}" | base64 --decode)
To connect to your Redis server:
1. Run a Redis pod that you can use as a client:
kubectl run --namespace default test-redis-client --rm --tty -i --restart='Never' \
--env REDIS_PASSWORD=$REDIS_PASSWORD \
--image docker.io/bitnami/redis:5.0.8-debian-10-r39 -- bash
2. Connect using the Redis CLI:
redis-cli -h test-redis-master -a $REDIS_PASSWORD
redis-cli -h test-redis-slave -a $REDIS_PASSWORD
To connect to your database from outside the cluster execute the following commands:
kubectl port-forward --namespace default svc/test-redis-master 6379:6379 &
redis-cli -h 127.0.0.1 -p 6379 -a $REDIS_PASSWORD
Verifying your Redis
After installing the chart, follow the instructions on your console to test your Redis deployment.
s # export REDIS_PASSWORD=$(kubectl get secret --namespace default test-redis \ > -o jsonpath="{.data.redis-password}" | base64 --decode) # kubectl run --namespace default test-redis-client --rm --tty -i --restart='Never' \ > --env REDIS_PASSWORD=$REDIS_PASSWORD \ > --image docker.io/bitnami/redis:5.0.7-debian-10-r32 -- bash If you don't see a command prompt, try pressing enter. I have no name!@test-redis-client:/$ redis-cli -h test-redis-master -a $REDIS_PASSWORD Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. test-redis-master:6379> cluster info ERR This instance has cluster support disabled test-redis-master:6379> ping PONG test-redis-master:6379> exit I have no name!@test-redis-client:/$ exit exit pod "test-redis-client" deleted
Cleaning up
To clean up your cluster, simply delete your Redis installation. You can use helm list to get the Redis release, and then helm delete [REDIS_RELEASE].
# helm list NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION test-redis default 1 2020-04-14 14:23:46 deployed redis-10.5.7 5.0.7 # helm delete test-redis release "test-redis" uninstalled