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487 lines
16 KiB
# Using Helm
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This guide explains the basics of using Helm (and Tiller) to manage
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packages on your Kubernetes cluster. It assumes that you have already
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[installed](install.md) the Helm client and the Tiller server (typically by `helm
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init`).
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If you are simply interested in running a few quick commands, you may
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wish to begin with the [Quickstart Guide](quickstart.md). This chapter
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covers the particulars of Helm commands, and explains how to use Helm.
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## Three Big Concepts
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A *Chart* is a Helm package. It contains all of the resource definitions
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necessary to run an application, tool, or service inside of a Kubernetes
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cluster. Think of it like the Kubernetes equivalent of a Homebrew formula,
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an Apt dpkg, or a Yum RPM file.
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A *Repository* is the place where charts can be collected and shared.
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It's like Perl's [CPAN archive](http://www.cpan.org) or the
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[Fedora Package Database](https://admin.fedoraproject.org/pkgdb/), but for
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Kubernetes packages.
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A *Release* is an instance of a chart running in a Kubernetes cluster.
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One chart can often be installed many times into the same cluster. And
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each time it is installed, a new _release_ is created. Consider a MySQL
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chart. If you want two databases running in your cluster, you can
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install that chart twice. Each one will have its own _release_, which
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will in turn have its own _release name_.
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With these concepts in mind, we can now explain Helm like this:
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Helm installs _charts_ into Kubernetes, creating a new _release_ for
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each installation. And to find new charts, you can search Helm chart
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_repositories_.
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## 'helm search': Finding Charts
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When you first install Helm, it is preconfigured to talk to the official
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Kubernetes charts repository. This repository contains a number of
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carefully curated and maintained charts. This chart repository is named
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`stable` by default.
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You can see which charts are available by running `helm search`:
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```
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$ helm search
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NAME VERSION DESCRIPTION
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stable/drupal 0.3.2 One of the most versatile open source content m...
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stable/jenkins 0.1.0 A Jenkins Helm chart for Kubernetes.
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stable/mariadb 0.5.1 Chart for MariaDB
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stable/mysql 0.1.0 Chart for MySQL
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...
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```
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With no filter, `helm search` shows you all of the available charts. You
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can narrow down your results by searching with a filter:
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```
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$ helm search mysql
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NAME VERSION DESCRIPTION
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stable/mysql 0.1.0 Chart for MySQL
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stable/mariadb 0.5.1 Chart for MariaDB
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```
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Now you will only see the results that match your filter.
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Why is
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`mariadb` in the list? Because its package description relates it to
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MySQL. We can use `helm inspect chart` to see this:
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```
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$ helm inspect stable/mariadb
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Fetched stable/mariadb to mariadb-0.5.1.tgz
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description: Chart for MariaDB
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engine: gotpl
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home: https://mariadb.org
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keywords:
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- mariadb
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- mysql
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- database
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- sql
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...
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```
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Search is a good way to find available packages. Once you have found a
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package you want to install, you can use `helm install` to install it.
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## 'helm install': Installing a Package
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To install a new package, use the `helm install` command. At its
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simplest, it takes only one argument: The name of the chart.
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```
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$ helm install stable/mariadb
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Fetched stable/mariadb-0.3.0 to /Users/mattbutcher/Code/Go/src/k8s.io/helm/mariadb-0.3.0.tgz
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happy-panda
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Last Deployed: Wed Sep 28 12:32:28 2016
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Namespace: default
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Status: DEPLOYED
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Resources:
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==> extensions/Deployment
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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happy-panda-mariadb 1 0 0 0 1s
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==> v1/Secret
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NAME TYPE DATA AGE
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happy-panda-mariadb Opaque 2 1s
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==> v1/Service
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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happy-panda-mariadb 10.0.0.70 <none> 3306/TCP 1s
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Notes:
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MariaDB can be accessed via port 3306 on the following DNS name from within your cluster:
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happy-panda-mariadb.default.svc.cluster.local
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To connect to your database run the following command:
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kubectl run happy-panda-mariadb-client --rm --tty -i --image bitnami/mariadb --command -- mysql -h happy-panda-mariadb
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```
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Now the `mariadb` chart is installed. Note that installing a chart
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creates a new _release_ object. The release above is named
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`happy-panda`. (If you want to use your own release name, simply use the
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`--name` flag on `helm install`.)
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During installation, the `helm` client will print useful information
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about which resources were created, what the state of the release is,
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and also whether there are additional configuration steps you can or
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should take.
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Helm does not wait until all of the resources are running before it
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exits. Many charts require Docker images that are over 600M in size, and
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may take a long time to install into the cluster.
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To keep track of a release's state, or to re-read configuration
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information, you can use `helm status`:
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```
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$ helm status happy-panda
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Last Deployed: Wed Sep 28 12:32:28 2016
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Namespace: default
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Status: DEPLOYED
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Resources:
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==> v1/Service
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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happy-panda-mariadb 10.0.0.70 <none> 3306/TCP 4m
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==> extensions/Deployment
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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happy-panda-mariadb 1 1 1 1 4m
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==> v1/Secret
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NAME TYPE DATA AGE
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happy-panda-mariadb Opaque 2 4m
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Notes:
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MariaDB can be accessed via port 3306 on the following DNS name from within your cluster:
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happy-panda-mariadb.default.svc.cluster.local
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To connect to your database run the following command:
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kubectl run happy-panda-mariadb-client --rm --tty -i --image bitnami/mariadb --command -- mysql -h happy-panda-mariadb
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```
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The above shows the current state of your release.
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### Customizing the Chart Before Installing
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Installing the way we have here will only use the default configuration
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options for this chart. Many times, you will want to customize the chart
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to use your preferred configuration.
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To see what options are configurable on a chart, use `helm inspect
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values`:
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```console
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helm inspect values stable/mariadb
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Fetched stable/mariadb-0.3.0.tgz to /Users/mattbutcher/Code/Go/src/k8s.io/helm/mariadb-0.3.0.tgz
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## Bitnami MariaDB image version
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## ref: https://hub.docker.com/r/bitnami/mariadb/tags/
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##
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## Default: none
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imageTag: 10.1.14-r3
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## Specify a imagePullPolicy
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## Default to 'Always' if imageTag is 'latest', else set to 'IfNotPresent'
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## ref: http://kubernetes.io/docs/user-guide/images/#pre-pulling-images
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##
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# imagePullPolicy:
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## Specify password for root user
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## ref: https://github.com/bitnami/bitnami-docker-mariadb/blob/master/README.md#setting-the-root-password-on-first-run
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##
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# mariadbRootPassword:
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## Create a database user
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## ref: https://github.com/bitnami/bitnami-docker-mariadb/blob/master/README.md#creating-a-database-user-on-first-run
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##
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# mariadbUser:
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# mariadbPassword:
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## Create a database
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## ref: https://github.com/bitnami/bitnami-docker-mariadb/blob/master/README.md#creating-a-database-on-first-run
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##
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# mariadbDatabase:
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```
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You can then override any of these settings in a YAML formatted file,
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and then pass that file during installation.
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```console
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$ echo 'mariadbUser: user0` > config.yaml
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$ helm install -f config.yaml stable/mariadb
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```
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The above will set the default MariaDB user to `user0`, but accept all
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the rest of the defaults for that chart.
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There are two ways to pass configuration data during install:
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- `--values` (or `-f`): Specify a YAML file with overrides. This can be specified multiple times
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and the rightmost file will take precedence
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- `--set`: Specify overrides on the command line.
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If both are used, `--set` values are merged into `--values` with higher precedence.
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#### The Format and Limitations of `--set`
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The `--set` option takes zero or more name/value pairs. At its simplest, it is
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used like this: `--set name=value`. The YAML equivalent of that is:
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```yaml
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name: value
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```
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Multiple values are separated by `,` characters. So `--set a=b,c=d` becomes:
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```yaml
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a: b
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c: d
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```
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More complex expressions are supported. For example, `--set outer.inner=value` is
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translated into this:
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```yaml
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outer:
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inner: value
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```
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Lists can be expressed by enclosing values in `{` and `}`. For example,
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`--set name={a, b, c}` translates to:
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```yaml
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name:
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- a
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- b
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- c
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```
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Sometimes you need to use special characters in your `--set` lines. You can use
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a backslash to escape the characters; `--set name=value1\,value2` will become:
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```yaml
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name: "value1,value2"
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```
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Similarly, you can escape dot sequences as well, which may come in handy when charts use the
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`toYaml` function to parse annotations, labels and node selectors. The syntax for
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`--set nodeSelector."kubernetes\.io/role"=master` becomes:
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```yaml
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nodeSelector:
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kubernetes.io/role: master
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```
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The `--set` syntax is not as expressive as YAML, especially when it comes to
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collections. And there is currently no method for expressing things such as "set
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the third item in a list to...".
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### More Installation Methods
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The `helm install` command can install from several sources:
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- A chart repository (as we've seen above)
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- A local chart archive (`helm install foo-0.1.1.tgz`)
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- An unpacked chart directory (`helm install path/to/foo`)
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- A full URL (`helm install https://example.com/charts/foo-1.2.3.tgz`)
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## 'helm upgrade' and 'helm rollback': Upgrading a Release, and Recovering on Failure
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When a new version of a chart is released, or when you want to change
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the configuration of your release, you can use the `helm upgrade`
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command.
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An upgrade takes an existing release and upgrades it according to the
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information you provide. Because Kubernetes charts can be large and
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complex, Helm tries to perform the least invasive upgrade. It will only
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update things that have changed since the last release.
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```console
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$ helm upgrade -f panda.yaml happy-panda stable/mariadb
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Fetched stable/mariadb-0.3.0.tgz to /Users/mattbutcher/Code/Go/src/k8s.io/helm/mariadb-0.3.0.tgz
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happy-panda has been upgraded. Happy Helming!
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Last Deployed: Wed Sep 28 12:47:54 2016
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Namespace: default
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Status: DEPLOYED
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...
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```
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In the above case, the `happy-panda` release is upgraded with the same
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chart, but with a new YAML file:
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```yaml
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mariadbUser: user1
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```
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We can use `helm get values` to see whether that new setting took
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effect.
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```console
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$ helm get values happy-panda
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mariadbUser: user1
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```
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The `helm get` command is a useful tool for looking at a release in the
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cluster. And as we can see above, it shows that our new values from
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`panda.yaml` were deployed to the cluster.
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Now, if something does not go as planned during a release, it is easy to
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roll back to a previous release using `helm rollback [RELEASE] [REVISION]`.
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```console
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$ helm rollback happy-panda 1
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```
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The above rolls back our happy-panda to its very first release version.
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A release version is an incremental revision. Every time an install,
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upgrade, or rollback happens, the revision number is incremented by 1.
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The first revision number is always 1. And we can use `helm history [RELEASE]`
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to see revision numbers for a certain release.
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## Helpful Options for Install/Upgrade/Rollback
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There are several other helpful options you can specify for customizing the
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behavior of Helm during an install/upgrade/rollback. Please note that this
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is not a full list of cli flags. To see a description of all flags, just run
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`helm <command> --help`.
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- `--timeout`: A value in seconds to wait for Kubernetes commands to complete
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This defaults to 300 (5 minutes)
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- `--wait`: Waits until all Pods are in a ready state, PVCs are bound, Deployments
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have minimum (`Desired` minus `maxUnavailable`) Pods in ready state and
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Services have and IP address (and Ingress if a `LoadBalancer`) before
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marking the release as successful. It will wait for as long as the
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`--timeout` value. If timeout is reached, the release will be marked as
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`FAILED`.
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Note: In scenario where Deployment has `replicas` set to 1 and `maxUnavailable` is not set to 0 as part of rolling
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update strategy, `--wait` will return as ready as it has satisfied the minimum Pod in ready condition.
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- `--no-hooks`: This skips running hooks for the command
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- `--recreate-pods` (only available for `upgrade` and `rollback`): This flag
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will cause all pods to be recreated (with the exception of pods belonging to
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deployments)
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## 'helm delete': Deleting a Release
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When it is time to uninstall or delete a release from the cluster, use
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the `helm delete` command:
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```
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$ helm delete happy-panda
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```
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This will remove the release from the cluster. You can see all of your
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currently deployed releases with the `helm list` command:
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```
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$ helm list
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NAME VERSION UPDATED STATUS CHART
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inky-cat 1 Wed Sep 28 12:59:46 2016 DEPLOYED alpine-0.1.0
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```
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From the output above, we can see that the `happy-panda` release was
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deleted.
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However, Helm always keeps records of what releases happened. Need to
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see the deleted releases? `helm list --deleted` shows those, and `helm
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list --all` shows all of the releases (deleted and currently deployed,
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as well as releases that failed):
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```console
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⇒ helm list --all
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NAME VERSION UPDATED STATUS CHART
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happy-panda 2 Wed Sep 28 12:47:54 2016 DELETED mariadb-0.3.0
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inky-cat 1 Wed Sep 28 12:59:46 2016 DEPLOYED alpine-0.1.0
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kindred-angelf 2 Tue Sep 27 16:16:10 2016 DELETED alpine-0.1.0
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```
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Because Helm keeps records of deleted releases, a release name cannot be
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re-used. (If you _really_ need to re-use a release name, you can use the
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`--replace` flag, but it will simply re-use the existing release and
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replace its resources.)
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Note that because releases are preserved in this way, you can rollback a
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deleted resource, and have it re-activate.
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## 'helm repo': Working with Repositories
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So far, we've been installing charts only from the `stable` repository.
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But you can configure `helm` to use other repositories. Helm provides
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several repository tools under the `helm repo` command.
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You can see which repositories are configured using `helm repo list`:
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```console
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$ helm repo list
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NAME URL
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stable https://kubernetes-charts.storage.googleapis.com
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local http://localhost:8879/charts
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mumoshu https://mumoshu.github.io/charts
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```
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And new repositories can be added with `helm repo add`:
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```console
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$ helm repo add dev https://example.com/dev-charts
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```
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Because chart repositories change frequently, at any point you can make
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sure your Helm client is up to date by running `helm repo update`.
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## Creating Your Own Charts
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The [Chart Development Guide](charts.md) explains how to develop your own
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charts. But you can get started quickly by using the `helm create`
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command:
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```console
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$ helm create deis-workflow
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Creating deis-workflow
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```
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Now there is a chart in `./deis-workflow`. You can edit it and create
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your own templates.
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As you edit your chart, you can validate that it is well-formatted by
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running `helm lint`.
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When it's time to package the chart up for distribution, you can run the
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`helm package` command:
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```console
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$ helm package deis-workflow
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deis-workflow-0.1.0.tgz
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```
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And that chart can now easily be installed by `helm install`:
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```console
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$ helm install ./deis-workflow-0.1.0.tgz
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...
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```
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Charts that are archived can be loaded into chart repositories. See the
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documentation for your chart repository server to learn how to upload.
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Note: The `stable` repository is managed on the [Kubernetes Charts
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GitHub repository](https://github.com/kubernetes/charts). That project
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accepts chart source code, and (after audit) packages those for you.
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## Conclusion
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This chapter has covered the basic usage patterns of the `helm` client,
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including searching, installation, upgrading, and deleting. It has also
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covered useful utility commands like `helm status`, `helm get`, and
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`helm repo`.
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For more information on these commands, take a look at Helm's built-in
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help: `helm help`.
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In the next chapter, we look at the process of developing charts.
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