자주 묻는 질문

헬름 2와 헬름 3의 주요 차이점이 무엇인가요? 이 페이지는 자주 나오는 질문들로 도움을 드립니다.

이 문서를 개선하는 당신의 도움을 기대합니다. 정보를 추가, 수정, 삭제하려면, 이슈를 등록하거나 풀 리퀘스트(pull request)를 보내주세요.

헬름 2 이후 변화

이 문서는 헬름 3에 도입된 모든 주요 변경사항의 상세 목록입니다.

틸러(tiller) 제거

During the Helm 2 development cycle, we introduced Tiller. Tiller played an important role for teams working on a shared cluster - it made it possible for multiple different operators to interact with the same set of releases.

With role-based access controls (RBAC) enabled by default in Kubernetes 1.6, locking down Tiller for use in a production scenario became more difficult to manage. Due to the vast number of possible security policies, our stance was to provide a permissive default configuration. This allowed first-time users to start experimenting with Helm and Kubernetes without having to dive headfirst into the security controls. Unfortunately, this permissive configuration could grant a user a broad range of permissions they weren’t intended to have. DevOps and SREs had to learn additional operational steps when installing Tiller into a multi-tenant cluster.

After hearing how community members were using Helm in certain scenarios, we found that Tiller’s release management system did not need to rely upon an in-cluster operator to maintain state or act as a central hub for Helm release information. Instead, we could simply fetch information from the Kubernetes API server, render the Charts client-side, and store a record of the installation in Kubernetes.

Tiller’s primary goal could be accomplished without Tiller, so one of the first decisions we made regarding Helm 3 was to completely remove Tiller.

With Tiller gone, the security model for Helm is radically simplified. Helm 3 now supports all the modern security, identity, and authorization features of modern Kubernetes. Helm’s permissions are evaluated using your kubeconfig file. Cluster administrators can restrict user permissions at whatever granularity they see fit. Releases are still recorded in-cluster, and the rest of Helm’s functionality remains.

업그레이드 전략 개선: 3-방향 전략적 병합 패치

Helm 2 used a two-way strategic merge patch. During an upgrade, it compared the most recent chart's manifest against the proposed chart's manifest (the one supplied during helm upgrade). It compared the differences between these two charts to determine what changes needed to be applied to the resources in Kubernetes. If changes were applied to the cluster out-of-band (such as during a kubectl edit), those changes were not considered. This resulted in resources being unable to roll back to its previous state: because Helm only considered the last applied chart's manifest as its current state, if there were no changes in the chart's state, the live state was left unchanged.

In Helm 3, we now use a three-way strategic merge patch. Helm considers the old manifest, its live state, and the new manifest when generating a patch.

예시

Let's go through a few common examples what this change impacts.

라이브(live) 상태 변경시 롤백

Your team just deployed their application to production on Kubernetes using Helm. The chart contains a Deployment object where the number of replicas is set to three:

$ helm install myapp ./myapp

A new developer joins the team. On their first day while observing the production cluster, a horrible coffee-spilling-on-the-keyboard accident happens and they kubectl scale the production deployment from three replicas down to zero.

$ kubectl scale --replicas=0 deployment/myapp

Another developer on your team notices that the production site is down and decides to rollback the release to its previous state:

$ helm rollback myapp

What happens?

In Helm 2, it would generate a patch, comparing the old manifest against the new manifest. Because this is a rollback, it's the same manifest. Helm would determine that there is nothing to change because there is no difference between the old manifest and the new manifest. The replica count continues to stay at zero. Panic ensues.

In Helm 3, the patch is generated using the old manifest, the live state, and the new manifest. Helm recognizes that the old state was at three, the live state is at zero and the new manifest wishes to change it back to three, so it generates a patch to change the state back to three.

라이브 상태 변경시 업그레이드

Many service meshes and other controller-based applications inject data into Kubernetes objects. This can be something like a sidecar, labels, or other information. Previously if you had the given manifest rendered from a Chart:

containers:
- name: server
  image: nginx:2.0.0

And the live state was modified by another application to

containers:
- name: server
  image: nginx:2.0.0
- name: my-injected-sidecar
  image: my-cool-mesh:1.0.0

Now, you want to upgrade the nginx image tag to 2.1.0. So, you upgrade to a chart with the given manifest:

containers:
- name: server
  image: nginx:2.1.0

What happens?

In Helm 2, Helm generates a patch of the containers object between the old manifest and the new manifest. The cluster's live state is not considered during the patch generation.

The cluster's live state is modified to look like the following:

containers:
- name: server
  image: nginx:2.1.0

The sidecar pod is removed from live state. More panic ensues.

In Helm 3, Helm generates a patch of the containers object between the old manifest, the live state, and the new manifest. It notices that the new manifest changes the image tag to 2.1.0, but live state contains a sidecar container.

The cluster's live state is modified to look like the following:

containers:
- name: server
  image: nginx:2.1.0
- name: my-injected-sidecar
  image: my-cool-mesh:1.0.0

이제 릴리스 이름이 네임스페이스로 구획됨(scope)

With the removal of Tiller, the information about each release had to go somewhere. In Helm 2, this was stored in the same namespace as Tiller. In practice, this meant that once a name was used by a release, no other release could use that same name, even if it was deployed in a different namespace.

In Helm 3, information about a particular release is now stored in the same namespace as the release itself. This means that users can now helm install wordpress stable/wordpress in two separate namespaces, and each can be referred with helm list by changing the current namespace context (e.g. helm list --namespace foo).

With this greater alignment to native cluster namespaces, the helm list command no longer lists all releases by default. Instead, it will list only the releases in the namespace of your current kubernetes context (i.e. the namespace shown when you run kubectl config view --minify). It also means you must supply the --all-namespaces flag to helm list to get behaviour similar to Helm 2.

시크릿(secret)이 기본 스토리지 드라이버로

In Helm 3, Secrets are now used as the default storage driver. Helm 2 used ConfigMaps by default to store release information. In Helm 2.7.0, a new storage backend that uses Secrets for storing release information was implemented, and it is now the default starting in Helm 3.

Changing to Secrets as the Helm 3 default allows for additional security in protecting charts in conjunction with the release of Secret encryption in Kubernetes.

Encrypting secrets at rest became available as an alpha feature in Kubernetes 1.7 and became stable as of Kubernetes 1.13. This allows users to encrypt Helm release metadata at rest, and so it is a good starting point that can be expanded later into using something like Vault.

Go 임포트 경로 변경

In Helm 3, Helm switched the Go import path over from k8s.io/helm to helm.sh/helm/v3. If you intend to upgrade to the Helm 3 Go client libraries, make sure to change your import paths.

수용능력

스테이지 렌더링시에 사용가능한 .Capabilities 빌트인 객체가 간소화되었다.

빌트인 객체

JSON스키마로 차트 값 유효성 검사

A JSON Schema can now be imposed upon chart values. This ensures that values provided by the user follow the schema laid out by the chart maintainer, providing better error reporting when the user provides an incorrect set of values for a chart.

Validation occurs when any of the following commands are invoked:

• helm install
• helm upgrade
• helm template
• helm lint

See the documentation on Schema files for more information.

requirements.yaml이 Chart.yaml 안으로 통합

The Chart dependency management system moved from requirements.yaml and requirements.lock to Chart.yaml and Chart.lock. We recommend that new charts meant for Helm 3 use the new format. However, Helm 3 still understands Chart API version 1 (v1) and will load existing requirements.yaml files

In Helm 2, this is how a requirements.yaml looked:

dependencies:
- name: mariadb
  version: 5.x.x
  repository: https://kubernetes-charts.storage.googleapis.com/
  condition: mariadb.enabled
  tags:
    - database

In Helm 3, the dependency is expressed the same way, but now from your Chart.yaml:

dependencies:
- name: mariadb
  version: 5.x.x
  repository: https://kubernetes-charts.storage.googleapis.com/
  condition: mariadb.enabled
  tags:
    - database

Charts are still downloaded and placed in the charts/ directory, so subcharts vendored into the charts/ directory will continue to work without modification.

이제 설치시 이름(또는 --generate-name)은 필수사항

In Helm 2, if no name was provided, an auto-generated name would be given. In production, this proved to be more of a nuisance than a helpful feature. In Helm 3, Helm will throw an error if no name is provided with helm install.

For those who still wish to have a name auto-generated for you, you can use the --generate-name flag to create one for you.

OCI 레지스트리로 차트 푸시

This is an experimental feature introduced in Helm 3. To use, set the environment variable HELM_EXPERIMENTAL_OCI=1.

At a high level, a Chart Repository is a location where Charts can be stored and shared. The Helm client packs and ships Helm Charts to a Chart Repository. Simply put, a Chart Repository is a basic HTTP server that houses an index.yaml file and some packaged charts.

While there are several benefits to the Chart Repository API meeting the most basic storage requirements, a few drawbacks have started to show:

• Chart Repositories have a very hard time abstracting most of the security implementations required in a production environment. Having a standard API for authentication and authorization is very important in production scenarios.
• Helm’s Chart provenance tools used for signing and verifying the integrity and origin of a chart are an optional piece of the Chart publishing process.
• In multi-tenant scenarios, the same Chart can be uploaded by another tenant, costing twice the storage cost to store the same content. Smarter chart repositories have been designed to handle this, but it’s not a part of the formal specification.
• Using a single index file for search, metadata information, and fetching Charts has made it difficult or clunky to design around in secure multi-tenant implementations.

Docker’s Distribution project (also known as Docker Registry v2) is the successor to the Docker Registry project. Many major cloud vendors have a product offering of the Distribution project, and with so many vendors offering the same product, the Distribution project has benefited from many years of hardening, security best practices, and battle-testing.

Please have a look at helm help chart and helm help registry for more information on how to package a chart and push it to a Docker registry.

For more info, please see this page.

helm serve 제거

helm serve ran a local Chart Repository on your machine for development purposes. However, it didn't receive much uptake as a development tool and had numerous issues with its design. In the end, we decided to remove it and split it out as a plugin.

For a similar experience to helm serve, have a look at the local filesystem storage option in ChartMuseum and the servecm plugin.

라이브러리 차트 지원

Helm 3 supports a class of chart called a “library chart”. This is a chart that is shared by other charts, but does not create any release artifacts of its own. A library chart’s templates can only declare define elements. Globally scoped non-define content is simply ignored. This allows users to re-use and share snippets of code that can be re-used across many charts, avoiding redundancy and keeping charts DRY.

Library charts are declared in the dependencies directive in Chart.yaml, and are installed and managed like any other chart.

dependencies:
  - name: mylib
    version: 1.x.x
    repository: quay.io

We’re very excited to see the use cases this feature opens up for chart developers, as well as any best practices that arise from consuming library charts.

Chart.yaml apiVersion 격상

With the introduction of library chart support and the consolidation of requirements.yaml into Chart.yaml, clients that understood Helm 2's package format won't understand these new features. So, we bumped the apiVersion in Chart.yaml from v1 to v2.

helm create now creates charts using this new format, so the default apiVersion was bumped there as well.

Clients wishing to support both versions of Helm charts should inspect the apiVersion field in Chart.yaml to understand how to parse the package format.

XDG 베이스 디렉토리 지원

The XDG Base Directory Specification is a portable standard defining where configuration, data, and cached files should be stored on the filesystem.

In Helm 2, Helm stored all this information in ~/.helm (affectionately known as helm home), which could be changed by setting the $HELM_HOME environment variable, or by using the global flag --home.

In Helm 3, Helm now respects the following environment variables as per the XDG Base Directory Specification:

• $XDG_CACHE_HOME
• $XDG_CONFIG_HOME
• $XDG_DATA_HOME

Helm plugins are still passed $HELM_HOME as an alias to $XDG_DATA_HOME for backwards compatibility with plugins looking to use $HELM_HOME as a scratchpad environment.

Several new environment variables are also passed in to the plugin's environment to accommodate this change:

• $HELM_PATH_CACHE for the cache path
• $HELM_PATH_CONFIG for the config path
• $HELM_PATH_DATA for the data path

Helm plugins looking to support Helm 3 should consider using these new environment variables instead.

CLI 명령어 이름변경

In order to better align the verbiage from other package managers, helm delete was re-named to helm uninstall. helm delete is still retained as an alias to helm uninstall, so either form can be used.

In Helm 2, in order to purge the release ledger, the --purge flag had to be provided. This functionality is now enabled by default. To retain the previous behavior, use helm uninstall --keep-history.

Additionally, several other commands were re-named to accommodate the same conventions:

• helm inspect -> helm show
• helm fetch -> helm pull

These commands have also retained their older verbs as aliases, so you can continue to use them in either form.

네임스페이스 자동 생성

When creating a release in a namespace that does not exist, Helm 2 created the namespace. Helm 3 follows the behavior of other Kubernetes tooling and returns an error if the namespace does not exist. Helm 3 will create the namespace if you explicitly specify --create-namespace flag.

설치

헬름의 데비안/페도라/... 네이티브 패키지는 왜 없나요?

We'd love to provide these or point you toward a trusted provider. If you're interested in helping, we'd love it. This is how the Homebrew formula was started.

왜 curl ...|bash 스크립트를 제공하나요?

There is a script in our repository (scripts/get-helm-3) that can be executed as a curl ..|bash script. The transfers are all protected by HTTPS, and the script does some auditing of the packages it fetches. However, the script has all the usual dangers of any shell script.

We provide it because it is useful, but we suggest that users carefully read the script first. What we'd really like, though, are better packaged releases of Helm.

헬름 클라이언트 파일들을 기본값 말고 다른 곳에 두려면 어떻게 하나요?

헬름은 파일을 보관할 때 XDG 구조를 사용한다. 그 위치를 오버라이드(override)할 수 있는 환경변수가 있다.

• $XDG_CACHE_HOME: 캐시 파일 보관장소를 다른 곳으로 설정
• $XDG_CONFIG_HOME: 헬름 설정 파일 보관장소를 다른 곳으로 설정
• $XDG_DATA_HOME: 헬름 데이터 보관장소를 다른 곳으로 설정

기존 리포지터리들이 있다면, helm repo add...으로 다시 추가할 필요가 있음을 알아두자.

언인스톨

로컬 헬름을 삭제하고 싶어요. 그 파일들은 모두 어디에 있나요?

helm 바이너리에 따라, Helm는 일부 파일들을 다음 위치에 저장한다.

• $XDG_CACHE_HOME
• $XDG_CONFIG_HOME
• $XDG_DATA_HOME

The following table gives the default folder for each of these, by OS:

트러블슈팅

GKE (Google Container Engine)에서 "No SSH tunnels currently open"라고 나와요

Error: Error forwarding ports: error upgrading connection: No SSH tunnels currently open. Were the targets able to accept an ssh-key for user "gke-[redacted]"?

Another variation of the error message is:

Unable to connect to the server: x509: certificate signed by unknown authority

The issue is that your local Kubernetes config file must have the correct credentials.

When you create a cluster on GKE, it will give you credentials, including SSL certificates and certificate authorities. These need to be stored in a Kubernetes config file (Default: ~/.kube/config so that kubectl and helm can access them.

헬름 2에서 전환 후, helm list에는 릴리스들이 일부만 보여요(또는 안 보여요).

헬름 3는 이제 클러스터 네임스페이스를 사용하여 릴리스들을 구획한다는 사실을 깜빡했을지 모르겠다. 따라서, 릴리스를 참조하는 모든 명령어에 대해:

• 활성 쿠버네티스 컨텍스트(kubectl config view --minify 명령어로 확인)에서의 현재 네임스페이스를 그대로 따르거나
• --namespace/-n 플래그를 사용하여 올바른 네임스페이스를 지정해야 한다.
• 한편 helm list 명령어에 대해서는 --all-namespaces/-A 플래그를 지정할 수 한다.

이는 helm ls, helm uninstall, 그리고 릴리스를 참조하는 나머지 모든 helm 명령어에 적용된다.