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Merge pull request #15182 from thockin/registry-doc
Add a README for private registry
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Dawn Chen
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cluster/addons/registry/README.md
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cluster/addons/registry/README.md
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# Private Docker Registry in Kubernetes
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Kubernetes offers an optional private Docker registry addon, which you can turn
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on when you bring up a cluster or install later. This gives you a place to
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store truly private Docker images for your cluster.
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## How it works
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The private registry runs as a `Pod` in your cluster. It does not currently
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support SSL or authentication, which triggers Docker's "insecure registry"
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logic. To work around this, we run a proxy on each node in the cluster,
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exposing a port onto the node (via a hostPort), which Docker accepts as
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"secure", since it is accessed by `localhost`.
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## Turning it on
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Some cluster installs (e.g. GCE) support this as a cluster-birth flag. The
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`ENABLE_CLUSTER_REGISTRY` variable in `cluster/gce/config-default.sh` governs
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whether the registry is run or not. To set this flag, you can specify
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`KUBE_ENABLE_CLUSTER_REGISTRY=true` when running `kube-up.sh`. If your cluster
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does not include this flag, the following steps should work. Note that some of
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this is cloud-provider specific, so you may have to customize it a bit.
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### Make some storage
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The primary job of the registry is to store data. To do that we have to decide
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where to store it. For cloud environments that have networked storage, we can
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use Kubernetes's `PersistentVolume` abstraction. The following template is
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expanded by `salt` in the GCE cluster turnup, but can easily be adapted to
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other situations:
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<!-- BEGIN MUNGE: EXAMPLE registry-pv.yaml.in -->
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```yaml
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kind: PersistentVolume
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apiVersion: v1
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metadata:
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name: kube-system-kube-registry-pv
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labels:
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kubernetes.io/cluster-service: "true"
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spec:
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{% if pillar.get('cluster_registry_disk_type', '') == 'gce' %}
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capacity:
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storage: {{ pillar['cluster_registry_disk_size'] }}
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accessModes:
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- ReadWriteOnce
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gcePersistentDisk:
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pdName: "{{ pillar['cluster_registry_disk_name'] }}"
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fsType: "ext4"
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{% endif %}
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```
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<!-- END MUNGE: EXAMPLE registry-pv.yaml.in -->
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If, for example, you wanted to use NFS you would just need to change the
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`gcePersistentDisk` block to `nfs`. See
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[here](../../../docs/user-guide/volumes.md) for more details on volumes.
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Note that in any case, the storage (in the case the GCE PersistentDisk) must be
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created independently - this is not something Kubernetes manages for you (yet).
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### I don't want or don't have persistent storage
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If you are running in a place that doesn't have networked storage, or if you
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just want to kick the tires on this without commiting to it, you can easily
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adapt the `ReplicationController` specification below to use a simple
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`emptyDir` volume instead of a `persistentVolumeClaim`.
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## Claim the storage
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Now that the Kubernetes cluster knows that some storage exists, you can put a
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claim on that storage. As with the `PersistentVolume` above, you can start
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with the `salt` template:
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<!-- BEGIN MUNGE: EXAMPLE registry-pvc.yaml.in -->
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```yaml
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kind: PersistentVolumeClaim
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apiVersion: v1
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metadata:
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name: kube-registry-pvc
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namespace: kube-system
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labels:
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kubernetes.io/cluster-service: "true"
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spec:
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accessModes:
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- ReadWriteOnce
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resources:
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requests:
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storage: {{ pillar['cluster_registry_disk_size'] }}
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```
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<!-- END MUNGE: EXAMPLE registry-pvc.yaml.in -->
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This tells Kubernetes that you want to use storage, and the `PersistentVolume`
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you created before will be bound to this claim (unless you have other
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`PersistentVolumes` in which case those might get bound instead). This claim
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gives you the rigth to use this storage until you release the claim.
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## Run the registry
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Now we can run a Docker registry:
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<!-- BEGIN MUNGE: EXAMPLE registry-rc.yaml -->
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```yaml
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apiVersion: v1
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kind: ReplicationController
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metadata:
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name: kube-registry-v0
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namespace: kube-system
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labels:
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k8s-app: kube-registry
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version: v0
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kubernetes.io/cluster-service: "true"
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spec:
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replicas: 1
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selector:
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k8s-app: kube-registry
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version: v0
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template:
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metadata:
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labels:
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k8s-app: kube-registry
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version: v0
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kubernetes.io/cluster-service: "true"
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spec:
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containers:
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- name: registry
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image: registry:2
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resources:
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limits:
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cpu: 100m
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memory: 100Mi
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env:
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- name: REGISTRY_HTTP_ADDR
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value: :5000
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- name: REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY
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value: /var/lib/registry
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volumeMounts:
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- name: image-store
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mountPath: /var/lib/registry
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ports:
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- containerPort: 5000
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name: registry
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protocol: TCP
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volumes:
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- name: image-store
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persistentVolumeClaim:
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claimName: kube-registry-pvc
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```
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<!-- END MUNGE: EXAMPLE registry-rc.yaml -->
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## Expose the registry in the cluster
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Now that we have a registry `Pod` running, we can expose it as a Service:
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<!-- BEGIN MUNGE: EXAMPLE registry-svc.yaml -->
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: kube-registry
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namespace: kube-system
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labels:
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k8s-app: kube-registry
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kubernetes.io/cluster-service: "true"
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kubernetes.io/name: "KubeRegistry"
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spec:
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selector:
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k8s-app: kube-registry
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ports:
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- name: registry
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port: 5000
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protocol: TCP
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```
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<!-- END MUNGE: EXAMPLE registry-svc.yaml -->
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## Expose the registry on each node
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Now that we have a running `Service`, we need to expose it onto each Kubernetes
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`Node` so that Docker will see it as `localhost`. We can load a `Pod` on every
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node by dropping a YAML file into the kubelet config directory
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(/etc/kubernetes/manifests by default).
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<!-- BEGIN MUNGE: EXAMPLE ../../saltbase/salt/kube-registry-proxy/kube-registry-proxy.yaml -->
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: kube-registry-proxy
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namespace: kube-system
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spec:
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containers:
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- name: kube-registry-proxy
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image: gcr.io/google_containers/kube-registry-proxy:0.3
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resources:
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limits:
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cpu: 100m
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memory: 50Mi
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env:
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- name: REGISTRY_HOST
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value: kube-registry.kube-system.svc.cluster.local
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- name: REGISTRY_PORT
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value: "5000"
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- name: FORWARD_PORT
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value: "5000"
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ports:
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- name: registry
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containerPort: 5000
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hostPort: 5000
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```
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<!-- END MUNGE: EXAMPLE ../../saltbase/salt/kube-registry-proxy/kube-registry-proxy.yaml -->
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This ensures that port 5000 on each node is directed to the registry `Service`.
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You should be able to verify that it is running by hitting port 5000 with a web
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browser and getting a 404 error:
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```console
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$ curl localhost:5000
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404 page not found
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```
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## Using the registry
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To use an image hosted by this registry, simply say this in your `Pod`'s
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`spec.containers[].image` field:
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```yaml
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image: localhost:5000/user/container
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```
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Before you can use the registry, you have to be able to get images into it,
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though. If you are building an image on your Kubernetes `Node`, you can spell
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out `localhost:5000` when you build and push. More likely, though, you are
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building locally and want to push to your cluster.
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You can use `kubectl` to set up a port-forward from your local node to a
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running Pod:
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```console
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$ POD=$(kubectl get pods --namespace kube-system -l k8s-app=kube-registry \
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-o template--template '{{range .items}}{{.metadata.name}} {{.status.phase}}{{"\n"}}{{end}}' \
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| grep Running | head -1 | cut -f1 -d' ')
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$ kubectl port-forward --namespace kube-system $POD 5000:5000 &
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```
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Now you can build and push images on your local computer as
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`localhost:5000/yourname/container` and those images will be available inside
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your kubernetes cluster with the same name.
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## Future improvements
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* Use a NodePort Service instead of a per-node proxy process
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* Enable SSL with a cert signed by your cluster CA or provided by the user
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* Enable authentication
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* Allow port-forwarding to a Service rather than a pod (#15180)
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[]()
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@ -38,7 +38,6 @@ spec:
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- containerPort: 5000
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name: registry
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protocol: TCP
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# TODO: use a persistent volume claim
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volumes:
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- name: image-store
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persistentVolumeClaim:
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