Merge master into dev-1.21 to keep in sync

2021-03-26 21:26:43 +01:00
parent 9442bf8bbd 3db583a9cd
commit ca046d9b1f
200 changed files with 4310 additions and 2439 deletions
@@ -11,20 +11,20 @@ aliases:

 <!-- overview -->

-This document catalogs the communication paths between the control plane (really the apiserver) and the Kubernetes cluster. The intent is to allow users to customize their installation to harden the network configuration such that the cluster can be run on an untrusted network (or on fully public IPs on a cloud provider).
+This document catalogs the communication paths between the control plane (apiserver) and the Kubernetes cluster. The intent is to allow users to customize their installation to harden the network configuration such that the cluster can be run on an untrusted network (or on fully public IPs on a cloud provider).



 <!-- body -->

 ## Node to Control Plane
-Kubernetes has a "hub-and-spoke" API pattern. All API usage from nodes (or the pods they run) terminate at the apiserver (none of the other control plane components are designed to expose remote services). The apiserver is configured to listen for remote connections on a secure HTTPS port (typically 443) with one or more forms of client [authentication](/docs/reference/access-authn-authz/authentication/) enabled.
+Kubernetes has a "hub-and-spoke" API pattern. All API usage from nodes (or the pods they run) terminates at the apiserver. None of the other control plane components are designed to expose remote services. The apiserver is configured to listen for remote connections on a secure HTTPS port (typically 443) with one or more forms of client [authentication](/docs/reference/access-authn-authz/authentication/) enabled.
 One or more forms of [authorization](/docs/reference/access-authn-authz/authorization/) should be enabled, especially if [anonymous requests](/docs/reference/access-authn-authz/authentication/#anonymous-requests) or [service account tokens](/docs/reference/access-authn-authz/authentication/#service-account-tokens) are allowed.

 Nodes should be provisioned with the public root certificate for the cluster such that they can connect securely to the apiserver along with valid client credentials. A good approach is that the client credentials provided to the kubelet are in the form of a client certificate. See [kubelet TLS bootstrapping](/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/) for automated provisioning of kubelet client certificates.

 Pods that wish to connect to the apiserver can do so securely by leveraging a service account so that Kubernetes will automatically inject the public root certificate and a valid bearer token into the pod when it is instantiated.
-The `kubernetes` service (in all namespaces) is configured with a virtual IP address that is redirected (via kube-proxy) to the HTTPS endpoint on the apiserver.
+The `kubernetes` service (in `default` namespace) is configured with a virtual IP address that is redirected (via kube-proxy) to the HTTPS endpoint on the apiserver.

 The control plane components also communicate with the cluster apiserver over the secure port.

@@ -42,7 +42,7 @@ The connections from the apiserver to the kubelet are used for:
 * Attaching (through kubectl) to running pods.
 * Providing the kubelet's port-forwarding functionality.

-These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's serving certificate, which makes the connection subject to man-in-the-middle attacks, and **unsafe** to run over untrusted and/or public networks.
+These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's serving certificate, which makes the connection subject to man-in-the-middle attacks and **unsafe** to run over untrusted and/or public networks.

 To verify this connection, use the `--kubelet-certificate-authority` flag to provide the apiserver with a root certificate bundle to use to verify the kubelet's serving certificate.

@@ -53,20 +53,20 @@ Finally, [Kubelet authentication and/or authorization](/docs/reference/command-l

 ### apiserver to nodes, pods, and services

-The connections from the apiserver to a node, pod, or service default to plain HTTP connections and are therefore neither authenticated nor encrypted. They can be run over a secure HTTPS connection by prefixing `https:` to the node, pod, or service name in the API URL, but they will not validate the certificate provided by the HTTPS endpoint nor provide client credentials so while the connection will be encrypted, it will not provide any guarantees of integrity. These connections **are not currently safe** to run over untrusted and/or public networks.
+The connections from the apiserver to a node, pod, or service default to plain HTTP connections and are therefore neither authenticated nor encrypted. They can be run over a secure HTTPS connection by prefixing `https:` to the node, pod, or service name in the API URL, but they will not validate the certificate provided by the HTTPS endpoint nor provide client credentials. So while the connection will be encrypted, it will not provide any guarantees of integrity. These connections **are not currently safe** to run over untrusted or public networks.

 ### SSH tunnels

 Kubernetes supports SSH tunnels to protect the control plane to nodes communication paths. In this configuration, the apiserver initiates an SSH tunnel to each node in the cluster (connecting to the ssh server listening on port 22) and passes all traffic destined for a kubelet, node, pod, or service through the tunnel.
 This tunnel ensures that the traffic is not exposed outside of the network in which the nodes are running.

-SSH tunnels are currently deprecated so you shouldn't opt to use them unless you know what you are doing. The Konnectivity service is a replacement for this communication channel.
+SSH tunnels are currently deprecated, so you shouldn't opt to use them unless you know what you are doing. The Konnectivity service is a replacement for this communication channel.

 ### Konnectivity service

 {{< feature-state for_k8s_version="v1.18" state="beta" >}}

-As a replacement to the SSH tunnels, the Konnectivity service provides TCP level proxy for the control plane to cluster communication. The Konnectivity service consists of two parts: the Konnectivity server and the Konnectivity agents, running in the control plane network and the nodes network respectively. The Konnectivity agents initiate connections to the Konnectivity server and maintain the network connections.
+As a replacement to the SSH tunnels, the Konnectivity service provides TCP level proxy for the control plane to cluster communication. The Konnectivity service consists of two parts: the Konnectivity server in the control plane network and the Konnectivity agents in the nodes network. The Konnectivity agents initiate connections to the Konnectivity server and maintain the network connections.
 After enabling the Konnectivity service, all control plane to nodes traffic goes through these connections.

 Follow the [Konnectivity service task](/docs/tasks/extend-kubernetes/setup-konnectivity/) to set up the Konnectivity service in your cluster.
@@ -17,7 +17,7 @@ and contains the services necessary to run
 {{< glossary_tooltip text="Pods" term_id="pod" >}}

 Typically you have several nodes in a cluster; in a learning or resource-limited
-environment, you might have just one.
+environment, you might have only one node.

 The [components](/docs/concepts/overview/components/#node-components) on a node include the
 {{< glossary_tooltip text="kubelet" term_id="kubelet" >}}, a
@@ -237,6 +237,7 @@ responsible for:
 - Evicting all the pods from the node using graceful termination if
  the node continues to be unreachable. The default timeouts are 40s to start
  reporting ConditionUnknown and 5m after that to start evicting pods.
+
 The node controller checks the state of each node every `--node-monitor-period` seconds.

 #### Heartbeats
@@ -278,6 +279,7 @@ the same time:
  `--large-cluster-size-threshold` nodes - default 50), then evictions are stopped.
 - Otherwise, the eviction rate is reduced to `--secondary-node-eviction-rate`
  (default 0.01) per second.
+
 The reason these policies are implemented per availability zone is because one
 availability zone might become partitioned from the master while the others remain
 connected. If your cluster does not span multiple cloud provider availability zones,
@@ -427,7 +427,7 @@ poorly-behaved workloads that may be harming system health.
  histogram vector of queue lengths for the queues, broken down by
  the labels `priority_level` and `flow_schema`, as sampled by the
  enqueued requests.  Each request that gets queued contributes one
-  sample to its histogram, reporting the length of the queue just
+  sample to its histogram, reporting the length of the queue immediately
  after the request was added.  Note that this produces different
  statistics than an unbiased survey would.
    {{< note >}}
@@ -278,7 +278,7 @@ pod/my-nginx-2035384211-u3t6x labeled
 ```

 This first filters all pods with the label "app=nginx", and then labels them with the "tier=fe".
-To see the pods you just labeled, run:
+To see the pods you labeled, run:

 ```shell
 kubectl get pods -l app=nginx -L tier
@@ -411,7 +411,7 @@ and

 ## Disruptive updates

-In some cases, you may need to update resource fields that cannot be updated once initialized, or you may just want to make a recursive change immediately, such as to fix broken pods created by a Deployment. To change such fields, use `replace --force`, which deletes and re-creates the resource. In this case, you can modify your original configuration file:
+In some cases, you may need to update resource fields that cannot be updated once initialized, or you may want to make a recursive change immediately, such as to fix broken pods created by a Deployment. To change such fields, use `replace --force`, which deletes and re-creates the resource. In this case, you can modify your original configuration file:

 ```shell
 kubectl replace -f https://k8s.io/examples/application/nginx/nginx-deployment.yaml --force
@@ -39,7 +39,7 @@ There are several different proxies you may encounter when using Kubernetes:
    - proxies UDP, TCP and SCTP
    - does not understand HTTP
    - provides load balancing
-    - is just used to reach services
+    - is only used to reach services

 1.  A Proxy/Load-balancer in front of apiserver(s):

@@ -72,8 +72,7 @@ You cannot overcommit `hugepages-*` resources.
 This is different from the `memory` and `cpu` resources.
 {{< /note >}}

-CPU and memory are collectively referred to as *compute resources*, or just
-*resources*. Compute
+CPU and memory are collectively referred to as *compute resources*, or *resources*. Compute
 resources are measurable quantities that can be requested, allocated, and
 consumed. They are distinct from
 [API resources](/docs/concepts/overview/kubernetes-api/). API resources, such as Pods and
@@ -554,7 +553,7 @@ extender.

 ### Consuming extended resources

-Users can consume extended resources in Pod specs just like CPU and memory.
+Users can consume extended resources in Pod specs like CPU and memory.
 The scheduler takes care of the resource accounting so that no more than the
 available amount is simultaneously allocated to Pods.

@@ -109,7 +109,7 @@ empty-secret   Opaque   0      2m6s
 ```

 The `DATA` column shows the number of data items stored in the Secret.
-In this case, `0` means we have just created an empty Secret.
+In this case, `0` means we have created an empty Secret.

 ###  Service account token Secrets

@@ -50,10 +50,11 @@ A more detailed description of the termination behavior can be found in
 ### Hook handler implementations

 Containers can access a hook by implementing and registering a handler for that hook.
-There are two types of hook handlers that can be implemented for Containers:
+There are three types of hook handlers that can be implemented for Containers:

 * Exec - Executes a specific command, such as `pre-stop.sh`, inside the cgroups and namespaces of the Container.
 Resources consumed by the command are counted against the Container.
+* TCP - Opens a TCP connecton against a specific port on the Container.
 * HTTP - Executes an HTTP request against a specific endpoint on the Container.

 ### Hook handler execution
@@ -135,7 +135,7 @@ Here are the recommended steps to configuring your nodes to use a private regist
 example, run these on your desktop/laptop:

   1. Run `docker login [server]` for each set of credentials you want to use.  This updates `$HOME/.docker/config.json` on your PC.
-   1. View `$HOME/.docker/config.json` in an editor to ensure it contains just the credentials you want to use.
+   1. View `$HOME/.docker/config.json` in an editor to ensure it contains only the credentials you want to use.
   1. Get a list of your nodes; for example:
      - if you want the names: `nodes=$( kubectl get nodes -o jsonpath='{range.items[*].metadata}{.name} {end}' )`
      - if you want to get the IP addresses: `nodes=$( kubectl get nodes -o jsonpath='{range .items[*].status.addresses[?(@.type=="ExternalIP")]}{.address} {end}' )`
@@ -145,7 +145,7 @@ Kubernetes provides several built-in authentication methods, and an [Authenticat

 ### Authorization

-[Authorization](/docs/reference/access-authn-authz/webhook/) determines whether specific users can read, write, and do other operations on API resources. It just works at the level of whole resources -- it doesn't discriminate based on arbitrary object fields. If the built-in authorization options don't meet your needs, and [Authorization webhook](/docs/reference/access-authn-authz/webhook/) allows calling out to user-provided code to make an authorization decision.
+[Authorization](/docs/reference/access-authn-authz/webhook/) determines whether specific users can read, write, and do other operations on API resources. It works at the level of whole resources -- it doesn't discriminate based on arbitrary object fields. If the built-in authorization options don't meet your needs, and [Authorization webhook](/docs/reference/access-authn-authz/webhook/) allows calling out to user-provided code to make an authorization decision.


 ### Dynamic Admission Control
@@ -146,7 +146,7 @@ Kubernetes provides several built-in authentication methods, and an [Authenticat

 ### Authorization

-[Authorization](/docs/reference/access-authn-authz/webhook/) determines whether specific users can read, write, and do other operations on API resources. It just works at the level of whole resources -- it doesn't discriminate based on arbitrary object fields. If the built-in authorization options don't meet your needs, and [Authorization webhook](/docs/reference/access-authn-authz/webhook/) allows calling out to user-provided code to make an authorization decision.
+[Authorization](/docs/reference/access-authn-authz/webhook/) determines whether specific users can read, write, and do other operations on API resources. It works at the level of whole resources -- it doesn't discriminate based on arbitrary object fields. If the built-in authorization options don't meet your needs, and [Authorization webhook](/docs/reference/access-authn-authz/webhook/) allows calling out to user-provided code to make an authorization decision.


 ### Dynamic Admission Control
@@ -28,7 +28,7 @@ resource can only be in one namespace.

 Namespaces are a way to divide cluster resources between multiple users (via [resource quota](/docs/concepts/policy/resource-quotas/)).

-It is not necessary to use multiple namespaces just to separate slightly different
+It is not necessary to use multiple namespaces to separate slightly different
 resources, such as different versions of the same software: use
 [labels](/docs/concepts/overview/working-with-objects/labels) to distinguish
 resources within the same namespace.
@@ -91,7 +91,7 @@ kubectl config view --minify | grep namespace:
 When you create a [Service](/docs/concepts/services-networking/service/),
 it creates a corresponding [DNS entry](/docs/concepts/services-networking/dns-pod-service/).
 This entry is of the form `<service-name>.<namespace-name>.svc.cluster.local`, which means
-that if a container just uses `<service-name>`, it will resolve to the service which
+that if a container only uses `<service-name>`, it will resolve to the service which
 is local to a namespace.  This is useful for using the same configuration across
 multiple namespaces such as Development, Staging and Production.  If you want to reach
 across namespaces, you need to use the fully qualified domain name (FQDN).
@@ -120,12 +120,12 @@ pod is eligible to be scheduled on, based on labels on the node.

 There are currently two types of node affinity, called `requiredDuringSchedulingIgnoredDuringExecution` and
 `preferredDuringSchedulingIgnoredDuringExecution`. You can think of them as "hard" and "soft" respectively,
-in the sense that the former specifies rules that *must* be met for a pod to be scheduled onto a node (just like
+in the sense that the former specifies rules that *must* be met for a pod to be scheduled onto a node (similar to
 `nodeSelector` but using a more expressive syntax), while the latter specifies *preferences* that the scheduler
 will try to enforce but will not guarantee. The "IgnoredDuringExecution" part of the names means that, similar
 to how `nodeSelector` works, if labels on a node change at runtime such that the affinity rules on a pod are no longer
-met, the pod will still continue to run on the node. In the future we plan to offer
-`requiredDuringSchedulingRequiredDuringExecution` which will be just like `requiredDuringSchedulingIgnoredDuringExecution`
+met, the pod continues to run on the node. In the future we plan to offer
+`requiredDuringSchedulingRequiredDuringExecution` which will be identical to `requiredDuringSchedulingIgnoredDuringExecution`
 except that it will evict pods from nodes that cease to satisfy the pods' node affinity requirements.

 Thus an example of `requiredDuringSchedulingIgnoredDuringExecution` would be "only run the pod on nodes with Intel CPUs"
@@ -43,7 +43,7 @@ Authenticators are described in more detail in
 [Authentication](/docs/reference/access-authn-authz/authentication/).

 The input to the authentication step is the entire HTTP request; however, it typically
-just examines the headers and/or client certificate.
+examines the headers and/or client certificate.

 Authentication modules include client certificates, password, and plain tokens,
 bootstrap tokens, and JSON Web Tokens (used for service accounts).
@@ -387,7 +387,7 @@ $ curl https://<EXTERNAL-IP>:<NODE-PORT> -k
 <h1>Welcome to nginx!</h1>
 ```

-Let's now recreate the Service to use a cloud load balancer, just change the `Type` of `my-nginx` Service from `NodePort` to `LoadBalancer`:
+Let's now recreate the Service to use a cloud load balancer. Change the `Type` of `my-nginx` Service from `NodePort` to `LoadBalancer`:

 ```shell
 kubectl edit svc my-nginx
@@ -260,7 +260,7 @@ There are existing Kubernetes concepts that allow you to expose a single Service
 {{< codenew file="service/networking/test-ingress.yaml" >}}

 If you create it using `kubectl apply -f` you should be able to view the state
-of the Ingress you just added:
+of the Ingress you added:

 ```bash
 kubectl get ingress test-ingress
@@ -57,7 +57,7 @@ the first label matches the originating Node's value for that label. If there is
 no backend for the Service on a matching Node, then the second label will be
 considered, and so forth, until no labels remain.

-If no match is found, the traffic will be rejected, just as if there were no
+If no match is found, the traffic will be rejected, as if there were no
 backends for the Service at all. That is, endpoints are chosen based on the first
 topology key with available backends. If this field is specified and all entries
 have no backends that match the topology of the client, the service has no
@@ -87,7 +87,7 @@ traffic as follows.

 * Service topology is not compatible with `externalTrafficPolicy=Local`, and
  therefore a Service cannot use both of these features. It is possible to use
-  both features in the same cluster on different Services, just not on the same
+  both features in the same cluster on different Services, only not on the same
  Service.

 * Valid topology keys are currently limited to `kubernetes.io/hostname`,
@@ -527,7 +527,7 @@ for NodePort use.

 Using a NodePort gives you the freedom to set up your own load balancing solution,
 to configure environments that are not fully supported by Kubernetes, or even
-to just expose one or more nodes' IPs directly.
+to expose one or more nodes' IPs directly.

 Note that this Service is visible as `<NodeIP>:spec.ports[*].nodePort`
 and `.spec.clusterIP:spec.ports[*].port`. (If the `--nodeport-addresses` flag in kube-proxy is set, <NodeIP> would be filtered NodeIP(s).)
@@ -785,8 +785,7 @@ you can use the following annotations:
 ```

 In the above example, if the Service contained three ports, `80`, `443`, and
-`8443`, then `443` and `8443` would use the SSL certificate, but `80` would just
-be proxied HTTP.
+`8443`, then `443` and `8443` would use the SSL certificate, but `80` would be proxied HTTP.

 From Kubernetes v1.9 onwards you can use [predefined AWS SSL policies](https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-security-policy-table.html) with HTTPS or SSL listeners for your Services.
 To see which policies are available for use, you can use the `aws` command line tool:
@@ -958,7 +957,8 @@ groups are modified with the following IP rules:

 | Rule | Protocol | Port(s) | IpRange(s) | IpRange Description |
 |------|----------|---------|------------|---------------------|
-| Health Check | TCP | NodePort(s) (`.spec.healthCheckNodePort` for `.spec.externalTrafficPolicy = Local`) | VPC CIDR | kubernetes.io/rule/nlb/health=\<loadBalancerName\> |
+| Health Check | TCP | NodePort(s) (`.spec.healthCheckNodePort` for `.spec.externalTrafficPolicy = Local`) | Subnet CIDR | kubernetes.io/rule/nlb/health=\<loadBalancerName\> |
+
 | Client Traffic | TCP | NodePort(s) | `.spec.loadBalancerSourceRanges` (defaults to `0.0.0.0/0`) | kubernetes.io/rule/nlb/client=\<loadBalancerName\> |
 | MTU Discovery | ICMP | 3,4 | `.spec.loadBalancerSourceRanges` (defaults to `0.0.0.0/0`) | kubernetes.io/rule/nlb/mtu=\<loadBalancerName\> |

@@ -1107,7 +1107,7 @@ but the current API requires it.

 ## Virtual IP implementation {#the-gory-details-of-virtual-ips}

-The previous information should be sufficient for many people who just want to
+The previous information should be sufficient for many people who want to
 use Services.  However, there is a lot going on behind the scenes that may be
 worth understanding.

@@ -29,7 +29,7 @@ A _PersistentVolume_ (PV) is a piece of storage in the cluster that has been pro

 A _PersistentVolumeClaim_ (PVC) is a request for storage by a user. It is similar to a Pod. Pods consume node resources and PVCs consume PV resources. Pods can request specific levels of resources (CPU and Memory).  Claims can request specific size and access modes (e.g., they can be mounted ReadWriteOnce, ReadOnlyMany or ReadWriteMany, see [AccessModes](#access-modes)).

-While PersistentVolumeClaims allow a user to consume abstract storage resources, it is common that users need PersistentVolumes with varying properties, such as performance, for different problems. Cluster administrators need to be able to offer a variety of PersistentVolumes that differ in more ways than just size and access modes, without exposing users to the details of how those volumes are implemented. For these needs, there is the _StorageClass_ resource.
+While PersistentVolumeClaims allow a user to consume abstract storage resources, it is common that users need PersistentVolumes with varying properties, such as performance, for different problems. Cluster administrators need to be able to offer a variety of PersistentVolumes that differ in more ways than size and access modes, without exposing users to the details of how those volumes are implemented. For these needs, there is the _StorageClass_ resource.

 See the [detailed walkthrough with working examples](/docs/tasks/configure-pod-container/configure-persistent-volume-storage/).

@@ -37,7 +37,7 @@ request a particular class. Administrators set the name and other parameters
 of a class when first creating StorageClass objects, and the objects cannot
 be updated once they are created.

-Administrators can specify a default StorageClass just for PVCs that don't
+Administrators can specify a default StorageClass only for PVCs that don't
 request any particular class to bind to: see the
 [PersistentVolumeClaim section](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims)
 for details.
@@ -569,7 +569,7 @@ parameters:
  `"http(s)://api-server:7860"`
 * `registry`: Quobyte registry to use to mount the volume. You can specify the
  registry as ``<host>:<port>`` pair or if you want to specify multiple
-  registries you just have to put a comma between them e.q.
+  registries, put a comma between them.
  ``<host1>:<port>,<host2>:<port>,<host3>:<port>``.
  The host can be an IP address or if you have a working DNS you can also
  provide the DNS names.
@@ -40,7 +40,7 @@ Users need to be aware of the following when using this feature:

 ## Provisioning

-Clones are provisioned just like any other PVC with the exception of adding a dataSource that references an existing PVC in the same namespace.
+Clones are provisioned like any other PVC with the exception of adding a dataSource that references an existing PVC in the same namespace.

 ```yaml
 apiVersion: v1
@@ -38,7 +38,7 @@ that run within the pod, and data is preserved across container restarts. When a
 ceases to exist, Kubernetes destroys ephemeral volumes; however, Kubernetes does not
 destroy persistent volumes.

-At its core, a volume is just a directory, possibly with some data in it, which
+At its core, a volume is a directory, possibly with some data in it, which
 is accessible to the containers in a pod. How that directory comes to be, the
 medium that backs it, and the contents of it are determined by the particular
 volume type used.
@@ -708,7 +708,7 @@ nginx-deployment-618515232    11        11        11        7m
 You can pause a Deployment before triggering one or more updates and then resume it. This allows you to
 apply multiple fixes in between pausing and resuming without triggering unnecessary rollouts.

-* For example, with a Deployment that was just created:
+* For example, with a Deployment that was created:
  Get the Deployment details:
  ```shell
  kubectl get deploy
@@ -100,7 +100,7 @@ pi-5rwd7
 ```

 Here, the selector is the same as the selector for the Job.  The `--output=jsonpath` option specifies an expression
-that just gets the name from each Pod in the returned list.
+with the name from each Pod in the returned list.

 View the standard output of one of the pods:

@@ -222,7 +222,7 @@ In this manner, a ReplicaSet can own a non-homogenous set of Pods
 ## Writing a ReplicaSet manifest

 As with all other Kubernetes API objects, a ReplicaSet needs the `apiVersion`, `kind`, and `metadata` fields.
-For ReplicaSets, the kind is always just ReplicaSet.
+For ReplicaSets, the `kind` is always a ReplicaSet.
 In Kubernetes 1.9 the API version `apps/v1` on the ReplicaSet kind is the current version and is enabled by default. The API version `apps/v1beta2` is deprecated.
 Refer to the first lines of the `frontend.yaml` example for guidance.

@@ -237,7 +237,7 @@ The `.spec.template` is a [pod template](/docs/concepts/workloads/pods/#pod-temp
 required to have labels in place. In our `frontend.yaml` example we had one label: `tier: frontend`.
 Be careful not to overlap with the selectors of other controllers, lest they try to adopt this Pod.

-For the template's [restart policy](/docs/concepts/workloads/Pods/pod-lifecycle/#restart-policy) field,
+For the template's [restart policy](/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy) field,
 `.spec.template.spec.restartPolicy`, the only allowed value is `Always`, which is the default.

 ### Pod Selector
@@ -110,8 +110,7 @@ nginx-3ntk0 nginx-4ok8v nginx-qrm3m

 Here, the selector is the same as the selector for the ReplicationController (seen in the
 `kubectl describe` output), and in a different form in `replication.yaml`.  The `--output=jsonpath` option
-specifies an expression that just gets the name from each pod in the returned list.
-
+specifies an expression with the name from each pod in the returned list.

 ## Writing a ReplicationController Spec

@@ -312,7 +312,7 @@ can specify a readiness probe that checks an endpoint specific to readiness that
 is different from the liveness probe.

 {{< note >}}
-If you just want to be able to drain requests when the Pod is deleted, you do not
+If you want to be able to drain requests when the Pod is deleted, you do not
 necessarily need a readiness probe; on deletion, the Pod automatically puts itself
 into an unready state regardless of whether the readiness probe exists.
 The Pod remains in the unready state while it waits for the containers in the Pod
@@ -39,8 +39,8 @@ Anyone can write a blog post and submit it for review.
  - Posts about other CNCF projects may or may not be on topic. We recommend asking the blog team before submitting a draft.
    - Many CNCF projects have their own blog. These are often a better choice for posts. There are times of major feature or milestone for a CNCF project that users would be interested in reading on the Kubernetes blog.
 - Blog posts should be original content
-    - The official blog is not for repurposing existing content from a third party as new content.
-    - The [license](https://github.com/kubernetes/website/blob/master/LICENSE) for the blog does allow commercial use of the content for commercial purposes, just not the other way around. 
+  - The official blog is not for repurposing existing content from a third party as new content.
+  - The [license](https://github.com/kubernetes/website/blob/master/LICENSE) for the blog allows commercial use of the content for commercial purposes, but not the other way around.
 - Blog posts should aim to be future proof
  - Given the development velocity of the project, we want evergreen content that won't require updates to stay accurate for the reader. 
  - It can be a better choice to add a tutorial or update official documentation than to write a high level overview as a blog post.
@@ -77,9 +77,8 @@ merged. Keep the following in mind:
  Alpha features.
 - It's hard to test (and therefore to document) a feature that hasn't been merged,
  or is at least considered feature-complete in its PR.
- Determining whether a feature needs documentation is a manual process and
-  just because a feature is not marked as needing docs doesn't mean it doesn't
-  need them.
+- Determining whether a feature needs documentation is a manual process. Even if
+  a feature is not marked as needing docs, you may need to document the feature.

 ## For developers or other SIG members

@@ -19,7 +19,7 @@ Attribute-based access control (ABAC) defines an access control paradigm whereby
 To enable `ABAC` mode, specify `--authorization-policy-file=SOME_FILENAME` and `--authorization-mode=ABAC` on startup.

 The file format is [one JSON object per line](https://jsonlines.org/).  There
-should be no enclosing list or map, just one map per line.
+should be no enclosing list or map, only one map per line.

 Each line is a "policy object", where each such object is a map with the following
 properties:
@@ -193,7 +193,7 @@ This admission controller will deny exec and attach commands to pods that run wi
 allow host access.  This includes pods that run as privileged, have access to the host IPC namespace, and
 have access to the host PID namespace.

-The DenyEscalatingExec admission plugin is deprecated and will be removed in v1.21.
+The DenyEscalatingExec admission plugin is deprecated.

 Use of a policy-based admission plugin (like [PodSecurityPolicy](#podsecuritypolicy) or a custom admission plugin)
 which can be targeted at specific users or Namespaces and also protects against creation of overly privileged Pods
@@ -206,7 +206,7 @@ is recommended instead.
 This admission controller will intercept all requests to exec a command in a pod if that pod has a privileged container.

 This functionality has been merged into [DenyEscalatingExec](#denyescalatingexec).
-The DenyExecOnPrivileged admission plugin is deprecated and will be removed in v1.21.
+The DenyExecOnPrivileged admission plugin is deprecated.

 Use of a policy-based admission plugin (like [PodSecurityPolicy](#podsecuritypolicy) or a custom admission plugin)
 which can be targeted at specific users or Namespaces and also protects against creation of overly privileged Pods
@@ -458,7 +458,7 @@ clusters:
  - name: name-of-remote-authn-service
    cluster:
      certificate-authority: /path/to/ca.pem         # CA for verifying the remote service.
-      server: https://authn.example.com/authenticate # URL of remote service to query. Must use 'https'.
+      server: https://authn.example.com/authenticate # URL of remote service to query. 'https' recommended for production.

 # users refers to the API server's webhook configuration.
 users:
@@ -138,7 +138,7 @@ no
 exposes the API server authorization to external services. Other resources in
 this group include:

-* `SubjectAccessReview` - Access review for any user, not just the current one. Useful for delegating authorization decisions to the API server. For example, the kubelet and extension API servers use this to determine user access to their own APIs.
+* `SubjectAccessReview` - Access review for any user, not only the current one. Useful for delegating authorization decisions to the API server. For example, the kubelet and extension API servers use this to determine user access to their own APIs.
 * `LocalSubjectAccessReview` - Like `SubjectAccessReview` but restricted to a specific namespace.
 * `SelfSubjectRulesReview` - A review which returns the set of actions a user can perform within a namespace. Useful for users to quickly summarize their own access, or for UIs to hide/show actions.

@@ -167,7 +167,7 @@ data:
    users: []
 ```

-The `kubeconfig` member of the ConfigMap is a config file with just the cluster
+The `kubeconfig` member of the ConfigMap is a config file with only the cluster
 information filled out.  The key thing being communicated here is the
 `certificate-authority-data`.  This may be expanded in the future.

@@ -196,8 +196,8 @@ O is the group that this user will belong to. You can refer to
 [RBAC](/docs/reference/access-authn-authz/rbac/) for standard groups.

 ```shell
-openssl genrsa -out john.key 2048
-openssl req -new -key john.key -out john.csr
+openssl genrsa -out myuser.key 2048
+openssl req -new -key myuser.key -out myuser.csr
 ```

 ### Create CertificateSigningRequest
@@ -209,7 +209,7 @@ cat <<EOF | kubectl apply -f -
 apiVersion: certificates.k8s.io/v1
 kind: CertificateSigningRequest
 metadata:
-  name: john
+  name: myuser
 spec:
  groups:
  - system:authenticated
@@ -224,7 +224,7 @@ Some points to note:

 - `usages` has to be '`client auth`'
 - `request` is the base64 encoded value of the CSR file content.
-  You can get the content using this command: ```cat john.csr | base64 | tr -d "\n"```
+  You can get the content using this command: ```cat myuser.csr | base64 | tr -d "\n"```

 ### Approve certificate signing request

@@ -239,7 +239,7 @@ kubectl get csr
 Approve the CSR:

 ```shell
-kubectl certificate approve john
+kubectl certificate approve myuser
 ```

 ### Get the certificate
@@ -247,11 +247,17 @@ kubectl certificate approve john
 Retrieve the certificate from the CSR:

 ```shell
-kubectl get csr/john -o yaml
+kubectl get csr/myuser -o yaml
 ```

 The certificate value is in Base64-encoded format under `status.certificate`.

+Export the issued certificate from the CertificateSigningRequest.
+
+```
+kubectl get csr myuser -o jsonpath='{.status.certificate}'| base64 -d > myuser.crt
+```
+
 ### Create Role and RoleBinding

 With the certificate created. it is time to define the Role and RoleBinding for
@@ -266,31 +272,30 @@ kubectl create role developer --verb=create --verb=get --verb=list --verb=update
 This is a sample command to create a RoleBinding for this new user:

 ```shell
-kubectl create rolebinding developer-binding-john --role=developer --user=john
+kubectl create rolebinding developer-binding-myuser --role=developer --user=myuser
 ```

 ### Add to kubeconfig

 The last step is to add this user into the kubeconfig file.
-This example assumes the key and certificate files are located at "/home/vagrant/work/".

 First, you need to add new credentials:

 ```
-kubectl config set-credentials john --client-key=/home/vagrant/work/john.key --client-certificate=/home/vagrant/work/john.crt --embed-certs=true
+kubectl config set-credentials myuser --client-key=myuser.key --client-certificate=myuser.crt --embed-certs=true

 ```

 Then, you need to add the context:

 ```
-kubectl config set-context john --cluster=kubernetes --user=john
+kubectl config set-context myuser --cluster=kubernetes --user=myuser
 ```

-To test it, change the context to `john`:
+To test it, change the context to `myuser`:

 ```
-kubectl config use-context john
+kubectl config use-context myuser
 ```

 ## Approval or rejection  {#approval-rejection}
@@ -363,7 +368,7 @@ status:

 It's usual to set `status.conditions.reason` to a machine-friendly reason
 code using TitleCase; this is a convention but you can set it to anything
-you like. If you want to add a note just for human consumption, use the
+you like. If you want to add a note for human consumption, use the
 `status.conditions.message` field.

 ## Signing
@@ -438,4 +443,3 @@ status:
 * View the source code for the kube-controller-manager built in [approver](https://github.com/kubernetes/kubernetes/blob/32ec6c212ec9415f604ffc1f4c1f29b782968ff1/pkg/controller/certificates/approver/sarapprove.go)
 * For details of X.509 itself, refer to [RFC 5280](https://tools.ietf.org/html/rfc5280#section-3.1) section 3.1
 * For information on the syntax of PKCS#10 certificate signing requests, refer to [RFC 2986](https://tools.ietf.org/html/rfc2986)
-
@@ -219,7 +219,7 @@ the role that is granted to those subjects.
 1. A binding to a different role is a fundamentally different binding.
 Requiring a binding to be deleted/recreated in order to change the `roleRef`
 ensures the full list of subjects in the binding is intended to be granted
-the new role (as opposed to enabling accidentally modifying just the roleRef
+the new role (as opposed to enabling or accidentally modifying only the roleRef
 without verifying all of the existing subjects should be given the new role's
 permissions).

@@ -333,7 +333,7 @@ as a cluster administrator, include rules for custom resources, such as those se
 or aggregated API servers, to extend the default roles.

 For example: the following ClusterRoles let the "admin" and "edit" default roles manage the custom resource
-named CronTab, whereas the "view" role can perform just read actions on CronTab resources.
+named CronTab, whereas the "view" role can perform only read actions on CronTab resources.
 You can assume that CronTab objects are named `"crontabs"` in URLs as seen by the API server.

 ```yaml
@@ -185,9 +185,9 @@ systemd unit file perhaps) to enable the token file.  See docs
 further details.

 ### Authorize kubelet to create CSR
-Now that the bootstrapping node is _authenticated_ as part of the `system:bootstrappers` group, it needs to be _authorized_ to create a certificate signing request (CSR) as well as retrieve it when done. Fortunately, Kubernetes ships with a `ClusterRole` with precisely these (and just these) permissions, `system:node-bootstrapper`.
+Now that the bootstrapping node is _authenticated_ as part of the `system:bootstrappers` group, it needs to be _authorized_ to create a certificate signing request (CSR) as well as retrieve it when done. Fortunately, Kubernetes ships with a `ClusterRole` with precisely these (and only these) permissions, `system:node-bootstrapper`.

-To do this, you just need to create a `ClusterRoleBinding` that binds the `system:bootstrappers` group to the cluster role `system:node-bootstrapper`.
+To do this, you only need to create a `ClusterRoleBinding` that binds the `system:bootstrappers` group to the cluster role `system:node-bootstrapper`.

 ```
 # enable bootstrapping nodes to create CSR
@@ -345,7 +345,7 @@ The important elements to note are:
 * `token`: the token to use

 The format of the token does not matter, as long as it matches what kube-apiserver expects. In the above example, we used a bootstrap token.
-As stated earlier, _any_ valid authentication method can be used, not just tokens.
+As stated earlier, _any_ valid authentication method can be used, not only tokens.

 Because the bootstrap `kubeconfig` _is_ a standard `kubeconfig`, you can use `kubectl` to generate it. To create the above example file:

@@ -909,7 +909,7 @@ WindowsEndpointSliceProxying=true|false (ALPHA - default=false)<br/>
 <td colspan="2">--pod-infra-container-image string&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Default: `k8s.gcr.io/pause:3.2`</td>
 </tr>
 <tr>
-<td></td><td style="line-height: 130%; word-wrap: break-word;">The image whose network/IPC namespaces containers in each pod will use. This docker-specific flag only works when container-runtime is set to `docker`.</td>
+<td></td><td style="line-height: 130%; word-wrap: break-word;"> Specified image will not be pruned by the image garbage collector. When container-runtime is set to `docker`, all containers in each pod will use the network/ipc namespaces from this image. Other CRI implementations have their own configuration to set this image.</td>
 </tr>

 <tr>
@@ -14,7 +14,7 @@ tags:
 A Kubernetes {{< glossary_tooltip text="control plane" term_id="control-plane" >}} component
 that embeds cloud-specific control logic. The cloud controller manager lets you link your
 cluster into your cloud provider's API, and separates out the components that interact
-with that cloud platform from components that just interact with your cluster.
+with that cloud platform from components that only interact with your cluster.

 <!--more-->

@@ -360,7 +360,7 @@ Other operations for exploring API resources:
 ```bash
 kubectl api-resources --namespaced=true      # All namespaced resources
 kubectl api-resources --namespaced=false     # All non-namespaced resources
-kubectl api-resources -o name                # All resources with simple output (just the resource name)
+kubectl api-resources -o name                # All resources with simple output (only the resource name)
 kubectl api-resources -o wide                # All resources with expanded (aka "wide") output
 kubectl api-resources --verbs=list,get       # All resources that support the "list" and "get" request verbs
 kubectl api-resources --api-group=extensions # All resources in the "extensions" API group
@@ -387,6 +387,9 @@ Examples using `-o=custom-columns`:
 # All images running in a cluster
 kubectl get pods -A -o=custom-columns='DATA:spec.containers[*].image'

+# All images running in namespace: default, grouped by Pod
+kubectl get pods --namespace default --output=custom-columns="NAME:.metadata.name,IMAGE:.spec.containers[*].image"
+
 # All images excluding "k8s.gcr.io/coredns:1.6.2"
 kubectl get pods -A -o=custom-columns='DATA:spec.containers[?(@.image!="k8s.gcr.io/coredns:1.6.2")].image'

@@ -69,7 +69,7 @@ for example `create`, `get`, `describe`, `delete`.
 Flags that you specify from the command line override default values and any corresponding environment variables.
 {{< /caution >}}

-If you need help, just run `kubectl help` from the terminal window.
+If you need help, run `kubectl help` from the terminal window.

 ## Operations

@@ -123,7 +123,7 @@ If your configuration is not using the latest version it is **recommended** that
 the [kubeadm config migrate](/docs/reference/setup-tools/kubeadm/kubeadm-config/) command.

 For more information on the fields and usage of the configuration you can navigate to our API reference
-page and pick a version from [the list](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm#pkg-subdirectories).
+page and pick a version from [the list](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm#section-directories).

 ### Adding kube-proxy parameters {#kube-proxy}

@@ -116,7 +116,7 @@ The **certificates.k8s.io/v1beta1** API version of CertificateSigningRequest wil
 * All existing persisted objects are accessible via the new API
 * Notable changes in `certificates.k8s.io/v1`:
    * For API clients requesting certificates:
-        * `spec.signerName` is now required (see [known Kubernetes signers](https://kubernetes.io/docs/reference/access-authn-authz/certificate-signing-requests/#kubernetes-signers)), and requests for `kubernetes.io/legacy-unknown` are not allowed to be created via the `certificates.k8s.io/v1` API
+        * `spec.signerName` is now required (see [known Kubernetes signers](/docs/reference/access-authn-authz/certificate-signing-requests/#kubernetes-signers)), and requests for `kubernetes.io/legacy-unknown` are not allowed to be created via the `certificates.k8s.io/v1` API
        * `spec.usages` is now required, may not contain duplicate values, and must only contain known usages
    * For API clients approving or signing certificates:
        * `status.conditions` may not contain duplicate types
@@ -327,7 +327,7 @@ supported in API v1 must exist and function until API v1 is removed.

 ### Component config structures

-Component configs are versioned and managed just like REST resources.
+Component configs are versioned and managed similar to REST resources.

 ### Future work

@@ -209,9 +209,8 @@ would have failed due to conflicting ownership.

 The merging strategy, implemented with Server Side Apply, provides a generally
 more stable object lifecycle. Server Side Apply tries to merge fields based on
-the fact who manages them instead of overruling just based on values. This way
-it is intended to make it easier and more stable for multiple actors updating
-the same object by causing less unexpected interference.
+the actor who manages them instead of overruling based on values. This way
+multiple actors can update the same object without causing unexpected interference.

 When a user sends a "fully-specified intent" object to the Server Side Apply
 endpoint, the server merges it with the live object favoring the value in the
@@ -319,7 +318,7 @@ kubectl apply -f https://k8s.io/examples/application/ssa/nginx-deployment-replic
 ```

 If the apply results in a conflict with the HPA controller, then do nothing. The
-conflict just indicates the controller has claimed the field earlier in the
+conflict indicates the controller has claimed the field earlier in the
 process than it sometimes does.

 At this point the user may remove the `replicas` field from their configuration.
@@ -436,7 +435,7 @@ Data: [{"op": "replace", "path": "/metadata/managedFields", "value": [{}]}]

 This will overwrite the managedFields with a list containing a single empty
 entry that then results in the managedFields being stripped entirely from the
-object. Note that just setting the managedFields to an empty list will not
+object. Note that setting the managedFields to an empty list will not
 reset the field. This is on purpose, so managedFields never get stripped by
 clients not aware of the field.

@@ -69,10 +69,9 @@ When creating a cluster, you can (using custom tooling):
 ## Addon resources

 Kubernetes [resource limits](/docs/concepts/configuration/manage-resources-containers/)
-help to minimise the impact of memory leaks and other ways that pods and containers can
-impact on other components. These resource limits can and should apply to
-{{< glossary_tooltip text="addon" term_id="addons" >}} just as they apply to application
-workloads.
+help to minimize the impact of memory leaks and other ways that pods and containers can
+impact on other components. These resource limits apply to
+{{< glossary_tooltip text="addon" term_id="addons" >}} resources just as they apply to application workloads.

 For example, you can set CPU and memory limits for a logging component:

@@ -68,7 +68,7 @@ Kubespray provides the ability to customize many aspects of the deployment:
  * {{< glossary_tooltip term_id="cri-o" >}}
 * Certificate generation methods

-Kubespray customizations can be made to a [variable file](https://docs.ansible.com/ansible/playbooks_variables.html). If you are just getting started with Kubespray, consider using the Kubespray defaults to deploy your cluster and explore Kubernetes.
+Kubespray customizations can be made to a [variable file](https://docs.ansible.com/ansible/playbooks_variables.html). If you are getting started with Kubespray, consider using the Kubespray defaults to deploy your cluster and explore Kubernetes.

 ### (4/5) Deploy a Cluster

@@ -333,7 +333,7 @@ These features were added in Kubernetes v1.15:
 ##### DNS {#dns-limitations}

 * ClusterFirstWithHostNet is not supported for DNS. Windows treats all names with a '.' as a FQDN and skips PQDN resolution
-* On Linux, you have a DNS suffix list, which is used when trying to resolve PQDNs. On Windows, we only have 1 DNS suffix, which is the DNS suffix associated with that pod's namespace (mydns.svc.cluster.local for example). Windows can resolve FQDNs and services or names resolvable with just that suffix. For example, a pod spawned in the default namespace, will have the DNS suffix **default.svc.cluster.local**. On a Windows pod, you can resolve both **kubernetes.default.svc.cluster.local** and **kubernetes**, but not the in-betweens, like **kubernetes.default** or **kubernetes.default.svc**.
+* On Linux, you have a DNS suffix list, which is used when trying to resolve PQDNs. On Windows, we only have 1 DNS suffix, which is the DNS suffix associated with that pod's namespace (mydns.svc.cluster.local for example). Windows can resolve FQDNs and services or names resolvable with only that suffix. For example, a pod spawned in the default namespace, will have the DNS suffix **default.svc.cluster.local**. On a Windows pod, you can resolve both **kubernetes.default.svc.cluster.local** and **kubernetes**, but not the in-betweens, like **kubernetes.default** or **kubernetes.default.svc**.
 * On Windows, there are multiple DNS resolvers that can be used. As these come with slightly different behaviors, using the `Resolve-DNSName` utility for name query resolutions is recommended.

 ##### IPv6
@@ -363,9 +363,9 @@ There are no differences in how most of the Kubernetes APIs work for Windows. Th

 At a high level, these OS concepts are different:

-* Identity - Linux uses userID (UID) and groupID (GID) which are represented as integer types. User and group names are not canonical - they are just an alias in `/etc/groups` or `/etc/passwd` back to UID+GID. Windows uses a larger binary security identifier (SID) which is stored in the Windows Security Access Manager (SAM) database. This database is not shared between the host and containers, or between containers.
+* Identity - Linux uses userID (UID) and groupID (GID) which are represented as integer types. User and group names are not canonical - they are an alias in `/etc/groups` or `/etc/passwd` back to UID+GID. Windows uses a larger binary security identifier (SID) which is stored in the Windows Security Access Manager (SAM) database. This database is not shared between the host and containers, or between containers.
 * File permissions - Windows uses an access control list based on SIDs, rather than a bitmask of permissions and UID+GID
-* File paths - convention on Windows is to use `\` instead of `/`. The Go IO libraries typically accept both and just make it work, but when you're setting a path or command line that's interpreted inside a container, `\` may be needed.
+* File paths - convention on Windows is to use `\` instead of `/`. The Go IO libraries accept both types of file path separators. However, when you're setting a path or command line that's interpreted inside a container, `\` may be needed.
 * Signals - Windows interactive apps handle termination differently, and can implement one or more of these:
  * A UI thread handles well-defined messages including WM_CLOSE
  * Console apps handle ctrl-c or ctrl-break using a Control Handler
@@ -231,7 +231,7 @@ You have several options for connecting to nodes, pods and services from outside
    - Use a service with type `NodePort` or `LoadBalancer` to make the service reachable outside
      the cluster.  See the [services](/docs/concepts/services-networking/service/) and
      [kubectl expose](/docs/reference/generated/kubectl/kubectl-commands/#expose) documentation.
-    - Depending on your cluster environment, this may just expose the service to your corporate network,
+    - Depending on your cluster environment, this may only expose the service to your corporate network,
      or it may expose it to the internet.  Think about whether the service being exposed is secure.
      Does it do its own authentication?
    - Place pods behind services.  To access one specific pod from a set of replicas, such as for debugging,
@@ -283,7 +283,7 @@ at `https://104.197.5.247/api/v1/namespaces/kube-system/services/elasticsearch-l
 As mentioned above, you use the `kubectl cluster-info` command to retrieve the service's proxy URL. To create proxy URLs that include service endpoints, suffixes, and parameters, you append to the service's proxy URL:
 `http://`*`kubernetes_master_address`*`/api/v1/namespaces/`*`namespace_name`*`/services/`*`service_name[:port_name]`*`/proxy`

-If you haven't specified a name for your port, you don't have to specify *port_name* in the URL.
+If you haven't specified a name for your port, you don't have to specify *port_name* in the URL. You can also use the port number in place of the *port_name* for both named and unnamed ports.

 By default, the API server proxies to your service using http. To use https, prefix the service name with `https:`:
 `http://`*`kubernetes_master_address`*`/api/v1/namespaces/`*`namespace_name`*`/services/`*`https:service_name:[port_name]`*`/proxy`
@@ -291,9 +291,9 @@ By default, the API server proxies to your service using http. To use https, pre
 The supported formats for the name segment of the URL are:

 * `<service_name>` - proxies to the default or unnamed port using http
-* `<service_name>:<port_name>` - proxies to the specified port using http
+* `<service_name>:<port_name>` - proxies to the specified port name or port number using http
 * `https:<service_name>:` - proxies to the default or unnamed port using https (note the trailing colon)
-* `https:<service_name>:<port_name>` - proxies to the specified port using https
+* `https:<service_name>:<port_name>` - proxies to the specified port name or port number using https

 ##### Examples

@@ -357,7 +357,7 @@ There are several different proxies you may encounter when using Kubernetes:
    - proxies UDP and TCP
    - does not understand HTTP
    - provides load balancing
-    - is just used to reach services
+    - is only used to reach services

 1.  A Proxy/Load-balancer in front of apiserver(s):

@@ -7,7 +7,7 @@ min-kubernetes-server-version: v1.10

 <!-- overview -->

-This page shows how to use `kubectl port-forward` to connect to a Redis
+This page shows how to use `kubectl port-forward` to connect to a MongoDB
 server running in a Kubernetes cluster. This type of connection can be useful
 for database debugging.

@@ -19,25 +19,25 @@ for database debugging.

 * {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}

-* Install [redis-cli](http://redis.io/topics/rediscli).
+* Install [MongoDB Shell](https://www.mongodb.com/try/download/shell).




 <!-- steps -->

-## Creating Redis deployment and service
+## Creating MongoDB deployment and service

-1. Create a Deployment that runs Redis:
+1. Create a Deployment that runs MongoDB:

    ```shell
-    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-deployment.yaml
+    kubectl apply -f https://k8s.io/examples/application/guestbook/mongo-deployment.yaml
    ```

    The output of a successful command verifies that the deployment was created:

    ```
-    deployment.apps/redis-master created
+    deployment.apps/mongo created
    ```

    View the pod status to check that it is ready:
@@ -49,8 +49,8 @@ for database debugging.
    The output displays the pod created:

    ```
-    NAME                            READY     STATUS    RESTARTS   AGE
-    redis-master-765d459796-258hz   1/1       Running   0          50s
+    NAME                     READY   STATUS    RESTARTS   AGE
+    mongo-75f59d57f4-4nd6q   1/1     Running   0          2m4s
    ```

    View the Deployment's status:
@@ -62,8 +62,8 @@ for database debugging.
    The output displays that the Deployment was created:

    ```
-    NAME         READY   UP-TO-DATE   AVAILABLE   AGE
-    redis-master 1/1     1            1           55s
+    NAME    READY   UP-TO-DATE   AVAILABLE   AGE
+    mongo   1/1     1            1           2m21s
    ```

    The Deployment automatically manages a ReplicaSet.
@@ -76,50 +76,50 @@ for database debugging.
    The output displays that the ReplicaSet was created:

    ```
-    NAME                      DESIRED   CURRENT   READY     AGE
-    redis-master-765d459796   1         1         1         1m
+    NAME               DESIRED   CURRENT   READY   AGE
+    mongo-75f59d57f4   1         1         1       3m12s
    ```


-2. Create a Service to expose Redis on the network:
+2. Create a Service to expose MongoDB on the network:

    ```shell
-    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-service.yaml
+    kubectl apply -f https://k8s.io/examples/application/guestbook/mongo-service.yaml
    ```

    The output of a successful command verifies that the Service was created:

    ```
-    service/redis-master created
+    service/mongo created
    ```

    Check the Service created:

    ```shell
-    kubectl get service redis-master
+    kubectl get service mongo
    ```

    The output displays the service created:

    ```
-    NAME           TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
-    redis-master   ClusterIP   10.0.0.213   <none>        6379/TCP   27s
+    NAME    TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)     AGE
+    mongo   ClusterIP   10.96.41.183   <none>        27017/TCP   11s
    ```

-3. Verify that the Redis server is running in the Pod, and listening on port 6379:
+3. Verify that the MongoDB server is running in the Pod, and listening on port 27017:

    ```shell
-    # Change redis-master-765d459796-258hz to the name of the Pod
-    kubectl get pod redis-master-765d459796-258hz --template='{{(index (index .spec.containers 0).ports 0).containerPort}}{{"\n"}}'
+    # Change mongo-75f59d57f4-4nd6q to the name of the Pod
+    kubectl get pod mongo-75f59d57f4-4nd6q --template='{{(index (index .spec.containers 0).ports 0).containerPort}}{{"\n"}}'
    ```

-    The output displays the port for Redis in that Pod:
+    The output displays the port for MongoDB in that Pod:

    ```
-    6379
+    27017
    ```

-    (this is the TCP port allocated to Redis on the internet).
+    (this is the TCP port allocated to MongoDB on the internet).

 ## Forward a local port to a port on the Pod

@@ -127,39 +127,39 @@ for database debugging.


    ```shell
-    # Change redis-master-765d459796-258hz to the name of the Pod
-    kubectl port-forward redis-master-765d459796-258hz 7000:6379
+    # Change mongo-75f59d57f4-4nd6q to the name of the Pod
+    kubectl port-forward mongo-75f59d57f4-4nd6q 28015:27017
    ```

    which is the same as

    ```shell
-    kubectl port-forward pods/redis-master-765d459796-258hz 7000:6379
+    kubectl port-forward pods/mongo-75f59d57f4-4nd6q 28015:27017
    ```

    or

    ```shell
-    kubectl port-forward deployment/redis-master 7000:6379
+    kubectl port-forward deployment/mongo 28015:27017
    ```

    or

    ```shell
-    kubectl port-forward replicaset/redis-master 7000:6379
+    kubectl port-forward replicaset/mongo-75f59d57f4 28015:27017
    ```

    or

    ```shell
-    kubectl port-forward service/redis-master 7000:redis
+    kubectl port-forward service/mongo 28015:27017
    ```

    Any of the above commands works. The output is similar to this:

    ```
-    Forwarding from 127.0.0.1:7000 -> 6379
-    Forwarding from [::1]:7000 -> 6379
+    Forwarding from 127.0.0.1:28015 -> 27017
+    Forwarding from [::1]:28015 -> 27017
    ```

 {{< note >}}
@@ -168,22 +168,22 @@ for database debugging.

 {{< /note >}}

-2.  Start the Redis command line interface:
+2.  Start the MongoDB command line interface:

    ```shell
-    redis-cli -p 7000
+    mongosh --port 28015
    ```

-3.  At the Redis command line prompt, enter the `ping` command:
+3.  At the MongoDB command line prompt, enter the `ping` command:

    ```
-    ping
+    db.runCommand( { ping: 1 } )
    ```

    A successful ping request returns:

    ```
-    PONG
+    { ok: 1 }
    ```

 ### Optionally let _kubectl_ choose the local port {#let-kubectl-choose-local-port}
@@ -193,15 +193,22 @@ the local port and thus relieve you from having to manage local port conflicts,
 the slightly simpler syntax:

 ```shell
-kubectl port-forward deployment/redis-master :6379
+kubectl port-forward deployment/mongo :27017
+```
+
+The output is similar to this:
+
+```
+Forwarding from 127.0.0.1:63753 -> 27017
+Forwarding from [::1]:63753 -> 27017
 ```

 The `kubectl` tool finds a local port number that is not in use (avoiding low ports numbers,
 because these might be used by other applications). The output is similar to:

 ```
-Forwarding from 127.0.0.1:62162 -> 6379
-Forwarding from [::1]:62162 -> 6379
+Forwarding from 127.0.0.1:63753 -> 27017
+Forwarding from [::1]:63753 -> 27017
 ```


@@ -209,8 +216,8 @@ Forwarding from [::1]:62162 -> 6379

 ## Discussion

-Connections made to local port 7000 are forwarded to port 6379 of the Pod that
-is running the Redis server. With this connection in place, you can use your
+Connections made to local port 28015 are forwarded to port 27017 of the Pod that
+is running the MongoDB server. With this connection in place, you can use your
 local workstation to debug the database that is running in the Pod.

 {{< note >}}
@@ -31,7 +31,7 @@ You have several options for connecting to nodes, pods and services from outside
    - Use a service with type `NodePort` or `LoadBalancer` to make the service reachable outside
      the cluster.  See the [services](/docs/concepts/services-networking/service/) and
      [kubectl expose](/docs/reference/generated/kubectl/kubectl-commands/#expose) documentation.
-    - Depending on your cluster environment, this may just expose the service to your corporate network,
+    - Depending on your cluster environment, this may only expose the service to your corporate network,
      or it may expose it to the internet.  Think about whether the service being exposed is secure.
      Does it do its own authentication?
    - Place pods behind services.  To access one specific pod from a set of replicas, such as for debugging,
@@ -70,7 +70,7 @@ for details about addon manager and how to disable individual addons.

 1. Mark a StorageClass as default:

-      Similarly to the previous step, you need to add/set the annotation
+      Similar to the previous step, you need to add/set the annotation
      `storageclass.kubernetes.io/is-default-class=true`.

      ```bash
@@ -125,7 +125,16 @@ the URL schema.

 Similarly, to configure etcd with secure client communication, specify flags
 `--key-file=k8sclient.key` and `--cert-file=k8sclient.cert`, and use HTTPS as
-the URL schema.
+the URL schema. Here is an example on a client command that uses secure
+communication:
+
+```
+ETCDCTL_API=3 etcdctl --endpoints 10.2.0.9:2379 \
+  --cert=/etc/kubernetes/pki/etcd/server.crt \
+  --key=/etc/kubernetes/pki/etcd/server.key \
+  --cacert=/etc/kubernetes/pki/etcd/ca.crt \
+  member list
+```

 ### Limiting access of etcd clusters

@@ -269,6 +278,24 @@ If etcd is running on a storage volume that supports backup, such as Amazon
 Elastic Block Store, back up etcd data by taking a snapshot of the storage
 volume.

+### Snapshot using etcdctl options
+
+We can also take the snapshot using various options given by etcdctl. For example 
+
+```shell
+ETCDCTL_API=3 etcdctl --h 
+``` 
+
+will list various options available from etcdctl. For example, you can take a snapshot by specifying
+the endpoint, certificates etc as shown below:
+
+```shell
+ETCDCTL_API=3 etcdctl --endpoints=[127.0.0.1:2379] \
+  --cacert=<trusted-ca-file> --cert=<cert-file> --key=<key-file> \
+  snapshot save <backup-file-location>
+```
+where `trusted-ca-file`, `cert-file` and `key-file` can be obtained from the description of the etcd Pod.
+
 ## Scaling up etcd clusters

 Scaling up etcd clusters increases availability by trading off performance.
@@ -293,6 +320,12 @@ employed to recover the data of a failed cluster.
 Before starting the restore operation, a snapshot file must be present. It can
 either be a snapshot file from a previous backup operation, or from a remaining
 [data directory]( https://etcd.io/docs/current/op-guide/configuration/#--data-dir).
+Here is an example:
+
+```shell
+ETCDCTL_API=3 etcdctl --endpoints 10.2.0.9:2379 snapshot restore snapshotdb
+```
+
 For more information and examples on restoring a cluster from a snapshot file, see
 [etcd disaster recovery documentation](https://etcd.io/docs/current/op-guide/recovery/#restoring-a-cluster).

@@ -324,4 +357,3 @@ We also recommend restarting any components (e.g. `kube-scheduler`,
 stale data. Note that in practice, the restore takes a bit of time.  During the
 restoration, critical components will lose leader lock and restart themselves.
 {{< /note >}}
-
@@ -54,7 +54,7 @@ Host: k8s-master:8080
 ```

 Note that Kubernetes does not need to know what a dongle is or what a dongle is for.
-The preceding PATCH request just tells Kubernetes that your Node has four things that
+The preceding PATCH request tells Kubernetes that your Node has four things that
 you call dongles.

 Start a proxy, so that you can easily send requests to the Kubernetes API server:
@@ -9,24 +9,17 @@ content_type: concept

 <!-- overview -->

-In addition to Kubernetes core components like api-server, scheduler, controller-manager running on a master machine
-there are a number of add-ons which, for various reasons, must run on a regular cluster node (rather than the Kubernetes master).
+Kubernetes core components such as the API server, scheduler, and controller-manager run on a control plane node. However, add-ons must run on a regular cluster node.
 Some of these add-ons are critical to a fully functional cluster, such as metrics-server, DNS, and UI.
 A cluster may stop working properly if a critical add-on is evicted (either manually or as a side effect of another operation like upgrade)
 and becomes pending (for example when the cluster is highly utilized and either there are other pending pods that schedule into the space
 vacated by the evicted critical add-on pod or the amount of resources available on the node changed for some other reason).

 Note that marking a pod as critical is not meant to prevent evictions entirely; it only prevents the pod from becoming permanently unavailable.
-For static pods, this means it can't be evicted, but for non-static pods, it just means they will always be rescheduled.
-
-
-
+A static pod marked as critical, can't be evicted. However, a non-static pods marked as critical are always rescheduled.

 <!-- body -->

-
 ### Marking pod as critical

 To mark a Pod as critical, set priorityClassName for that Pod to `system-cluster-critical` or `system-node-critical`. `system-node-critical` is the highest available priority, even higher than `system-cluster-critical`.
-
-
@@ -35,7 +35,7 @@ and kubeadm will use this CA for signing the rest of the certificates.

 ## External CA mode {#external-ca-mode}

-It is also possible to provide just the `ca.crt` file and not the
+It is also possible to provide only the `ca.crt` file and not the
 `ca.key` file (this is only available for the root CA file, not other cert pairs).
 If all other certificates and kubeconfig files are in place, kubeadm recognizes
 this condition and activates the "External CA" mode. kubeadm will proceed without the
@@ -170,7 +170,7 @@ controllerManager:

 ### Create certificate signing requests (CSR)

-See [Create CertificateSigningRequest](https://kubernetes.io/docs/reference/access-authn-authz/certificate-signing-requests/#create-certificatesigningrequest) for creating CSRs with the Kubernetes API.
+See [Create CertificateSigningRequest](/docs/reference/access-authn-authz/certificate-signing-requests/#create-certificatesigningrequest) for creating CSRs with the Kubernetes API.

 ## Renew certificates with external CA

@@ -37,7 +37,7 @@ The upgrade workflow at high level is the following:

 ### Additional information

- [Draining nodes](https://kubernetes.io/docs/tasks/administer-cluster/safely-drain-node/) before kubelet MINOR version
+- [Draining nodes](/docs/tasks/administer-cluster/safely-drain-node/) before kubelet MINOR version
  upgrades is required. In the case of control plane nodes, they could be running CoreDNS Pods or other critical workloads.
 - All containers are restarted after upgrade, because the container spec hash value is changed.

@@ -50,7 +50,7 @@ and scheduling of Pods; on each node, the {{< glossary_tooltip text="kubelet" te
 uses the container runtime interface as an abstraction so that you can use any compatible
 container runtime.

-In its earliest releases, Kubernetes offered compatibility with just one container runtime: Docker.
+In its earliest releases, Kubernetes offered compatibility with one container runtime: Docker.
 Later in the Kubernetes project's history, cluster operators wanted to adopt additional container runtimes.
 The CRI was designed to allow this kind of flexibility - and the kubelet began supporting CRI. However,
 because Docker existed before the CRI specification was invented, the Kubernetes project created an
@@ -75,7 +75,7 @@ or execute something inside container using `docker exec`.

 If you're running workloads via Kubernetes, the best way to stop a container is through
 the Kubernetes API rather than directly through the container runtime (this advice applies
-for all container runtimes, not just Docker).
+for all container runtimes, not only Docker).

 {{< /note >}}

@@ -232,7 +232,7 @@ Apply the manifest to create a Deployment
 ```shell
 kubectl apply -f https://k8s.io/examples/admin/snowflake-deployment.yaml
 ```
-We have just created a deployment whose replica size is 2 that is running the pod called `snowflake` with a basic container that just serves the hostname.
+We have created a deployment whose replica size is 2 that is running the pod called `snowflake` with a basic container that serves the hostname.

 ```shell
 kubectl get deployment
@@ -196,7 +196,7 @@ This delete is asynchronous, so for a time you will see the namespace in the `Te
    ```shell
    kubectl create deployment snowflake --image=k8s.gcr.io/serve_hostname  -n=development --replicas=2
    ```
-    We have just created a deployment whose replica size is 2 that is running the pod called `snowflake` with a basic container that just serves the hostname.
+    We have created a deployment whose replica size is 2 that is running the pod called `snowflake` with a basic container that serves the hostname.

    ```shell
    kubectl get deployment -n=development
@@ -302,7 +302,7 @@ Use cases include:

 When you create a [Service](/docs/concepts/services-networking/service/), it creates a corresponding [DNS entry](/docs/concepts/services-networking/dns-pod-service/).
 This entry is of the form `<service-name>.<namespace-name>.svc.cluster.local`, which means
-that if a container just uses `<service-name>` it will resolve to the service which
+that if a container uses `<service-name>` it will resolve to the service which
 is local to a namespace.  This is useful for using the same configuration across
 multiple namespaces such as Development, Staging and Production.  If you want to reach
 across namespaces, you need to use the fully qualified domain name (FQDN).
@@ -20,7 +20,7 @@ Decide whether you want to deploy a [cloud](#creating-a-calico-cluster-with-goog

 **Prerequisite**: [gcloud](https://cloud.google.com/sdk/docs/quickstarts).

-1.  To launch a GKE cluster with Calico, just include the `--enable-network-policy` flag.
+1.  To launch a GKE cluster with Calico, include the `--enable-network-policy` flag.

    **Syntax**
    ```shell
@@ -128,8 +128,8 @@ curl -v -H 'Content-type: application/json' https://your-cluster-api-endpoint.ex

 The API can respond in one of three ways:

- If the eviction is granted, then the Pod is deleted just as if you had sent
-  a `DELETE` request to the Pod's URL and you get back `200 OK`.
+- If the eviction is granted, then the Pod is deleted as if you sent
+  a `DELETE` request to the Pod's URL and received back `200 OK`.
 - If the current state of affairs wouldn't allow an eviction by the rules set
  forth in the budget, you get back `429 Too Many Requests`. This is
  typically used for generic rate limiting of *any* requests, but here we mean
@@ -184,7 +184,7 @@ Where `YWRtaW5pc3RyYXRvcg==` decodes to `administrator`.

 ## Clean Up

-To delete the Secret you have just created:
+To delete the Secret you have created:

 ```shell
 kubectl delete secret mysecret
@@ -115,8 +115,7 @@ accidentally to an onlooker, or from being stored in a terminal log.

 ## Decoding the Secret  {#decoding-secret}

-To view the contents of the Secret we just created, you can run the following
-command:
+To view the contents of the Secret you created, run the following command:

 ```shell
 kubectl get secret db-user-pass -o jsonpath='{.data}'
@@ -125,10 +124,10 @@ kubectl get secret db-user-pass -o jsonpath='{.data}'
 The output is similar to:

 ```json
-{"password.txt":"MWYyZDFlMmU2N2Rm","username.txt":"YWRtaW4="}
+{"password":"MWYyZDFlMmU2N2Rm","username":"YWRtaW4="}
 ```

-Now you can decode the `password.txt` data:
+Now you can decode the `password` data:

 ```shell
 echo 'MWYyZDFlMmU2N2Rm' | base64 --decode
@@ -142,7 +141,7 @@ The output is similar to:

 ## Clean Up

-To delete the Secret you have just created:
+To delete the Secret you have created:

 ```shell
 kubectl delete secret db-user-pass
@@ -113,7 +113,7 @@ To check the actual content of the encoded data, please refer to

 ## Clean Up

-To delete the Secret you have just created:
+To delete the Secret you have created:

 ```shell
 kubectl delete secret db-user-pass-96mffmfh4k
@@ -112,7 +112,7 @@ kubectl top pod cpu-demo --namespace=cpu-example
 ```

 This example output shows that the Pod is using 974 milliCPU, which is
-just a bit less than the limit of 1 CPU specified in the Pod configuration.
+slightly less than the limit of 1 CPU specified in the Pod configuration.

 ```
 NAME                        CPU(cores)   MEMORY(bytes)
@@ -204,7 +204,7 @@ seconds.

 In addition to the readiness probe, this configuration includes a liveness probe.
 The kubelet will run the first liveness probe 15 seconds after the container
-starts. Just like the readiness probe, this will attempt to connect to the
+starts. Similar to the readiness probe, this will attempt to connect to the
 `goproxy` container on port 8080. If the liveness probe fails, the container
 will be restarted.

@@ -118,7 +118,7 @@ those secrets might also be visible to other users on your PC during the time th

 ## Inspecting the Secret `regcred`

-To understand the contents of the `regcred` Secret you just created, start by viewing the Secret in YAML format:
+To understand the contents of the `regcred` Secret you created, start by viewing the Secret in YAML format:

 ```shell
 kubectl get secret regcred --output=yaml
@@ -67,7 +67,7 @@ sudo yum -y install kompose
 {{% /tab %}}
 {{% tab name="Fedora package" %}}

-Kompose is in Fedora 24, 25 and 26 repositories. You can install it just like any other package.
+Kompose is in Fedora 24, 25 and 26 repositories. You can install it like any other package.

 ```bash
 sudo dnf -y install kompose
@@ -87,7 +87,7 @@ brew install kompose

 ## Use Kompose

-In just a few steps, we'll take you from Docker Compose to Kubernetes. All
+In a few steps, we'll take you from Docker Compose to Kubernetes. All
 you need is an existing `docker-compose.yml` file.

 1. Go to the directory containing your `docker-compose.yml` file. If you don't have one, test using this one.
@@ -177,7 +177,7 @@ kubectl describe pod nginx-deployment-1370807587-fz9sd

 Here you can see the event generated by the scheduler saying that the Pod failed to schedule for reason `FailedScheduling` (and possibly others).  The message tells us that there were not enough resources for the Pod on any of the nodes.

-To correct this situation, you can use `kubectl scale` to update your Deployment to specify four or fewer replicas. (Or you could just leave the one Pod pending, which is harmless.)
+To correct this situation, you can use `kubectl scale` to update your Deployment to specify four or fewer replicas. (Or you could leave the one Pod pending, which is harmless.)

 Events such as the ones you saw at the end of `kubectl describe pod` are persisted in etcd and provide high-level information on what is happening in the cluster. To list all events you can use

@@ -57,7 +57,7 @@ case you can try several things:
  will never be scheduled.

    You can check node capacities with the `kubectl get nodes -o <format>`
-    command. Here are some example command lines that extract just the necessary
+    command. Here are some example command lines that extract the necessary
    information:

    ```shell
@@ -178,7 +178,7 @@ kubectl expose deployment hostnames --port=80 --target-port=9376
 service/hostnames exposed
 ```

-And read it back, just to be sure:
+And read it back:

 ```shell
 kubectl get svc hostnames
@@ -427,8 +427,7 @@ hostnames-632524106-ly40y   1/1       Running   0          1h
 hostnames-632524106-tlaok   1/1       Running   0          1h
 ```

-The `-l app=hostnames` argument is a label selector - just like our Service
-has.
+The `-l app=hostnames` argument is a label selector configured on the Service.

 The "AGE" column says that these Pods are about an hour old, which implies that
 they are running fine and not crashing.
@@ -607,7 +606,7 @@ iptables-save | grep hostnames
 -A KUBE-PORTALS-HOST -d 10.0.1.175/32 -p tcp -m comment --comment "default/hostnames:default" -m tcp --dport 80 -j DNAT --to-destination 10.240.115.247:48577
 ```

-There should be 2 rules for each port of your Service (just one in this
+There should be 2 rules for each port of your Service (only one in this
 example) - a "KUBE-PORTALS-CONTAINER" and a "KUBE-PORTALS-HOST".

 Almost nobody should be using the "userspace" mode any more, so you won't spend
@@ -294,9 +294,9 @@ a running cluster in the [Deploying section](#deploying).

 ### Changing `DaemonSet` parameters

-When you have the Stackdriver Logging `DaemonSet` in your cluster, you can just modify the
-`template` field in its spec, daemonset controller will update the pods for you. For example,
-let's assume you've just installed the Stackdriver Logging as described above. Now you want to
+When you have the Stackdriver Logging `DaemonSet` in your cluster, you can modify the
+`template` field in its spec. The DaemonSet controller manages the pods for you.
+For example, assume you've installed the Stackdriver Logging as described above. Now you want to
 change the memory limit to give fluentd more memory to safely process more logs.

 Get the spec of `DaemonSet` running in your cluster:
@@ -12,7 +12,7 @@ weight: 20
 Kubernetes ships with a default scheduler that is described
 [here](/docs/reference/command-line-tools-reference/kube-scheduler/).
 If the default scheduler does not suit your needs you can implement your own scheduler.
-Not just that, you can even run multiple schedulers simultaneously alongside the default
+Moreover, you can even run multiple schedulers simultaneously alongside the default
 scheduler and instruct Kubernetes what scheduler to use for each of your pods. Let's
 learn how to run multiple schedulers in Kubernetes with an example.

@@ -30,7 +30,7 @@ in the Kubernetes source directory for a canonical example.
 ## Package the scheduler

 Package your scheduler binary into a container image. For the purposes of this example,
-let's just use the default scheduler (kube-scheduler) as our second scheduler as well.
+you can use the default scheduler (kube-scheduler) as your second scheduler.
 Clone the [Kubernetes source code from GitHub](https://github.com/kubernetes/kubernetes)
 and build the source.

@@ -61,9 +61,9 @@ gcloud docker -- push gcr.io/my-gcp-project/my-kube-scheduler:1.0

 ## Define a Kubernetes Deployment for the scheduler

-Now that we have our scheduler in a container image, we can just create a pod
-config for it and run it in our Kubernetes cluster. But instead of creating a pod
-directly in the cluster, let's use a [Deployment](/docs/concepts/workloads/controllers/deployment/)
+Now that you have your scheduler in a container image, create a pod
+configuration for it and run it in your Kubernetes cluster. But instead of creating a pod
+directly in the cluster, you can use a [Deployment](/docs/concepts/workloads/controllers/deployment/)
 for this example. A [Deployment](/docs/concepts/workloads/controllers/deployment/) manages a
 [Replica Set](/docs/concepts/workloads/controllers/replicaset/) which in turn manages the pods,
 thereby making the scheduler resilient to failures. Here is the deployment
@@ -83,7 +83,7 @@ detailed description of other command line arguments.

 ## Run the second scheduler in the cluster

-In order to run your scheduler in a Kubernetes cluster, just create the deployment
+In order to run your scheduler in a Kubernetes cluster, create the deployment
 specified in the config above in a Kubernetes cluster:

 ```shell
@@ -132,9 +132,9 @@ kubectl edit clusterrole system:kube-scheduler

 ## Specify schedulers for pods

-Now that our second scheduler is running, let's create some pods, and direct them
-to be scheduled by either the default scheduler or the one we just deployed.
-In order to schedule a given pod using a specific scheduler, we specify the name of the
+Now that your second scheduler is running, create some pods, and direct them
+to be scheduled by either the default scheduler or the one you deployed.
+In order to schedule a given pod using a specific scheduler, specify the name of the
 scheduler in that pod spec. Let's look at three examples.

 - Pod spec without any scheduler name
@@ -196,7 +196,7 @@ while the other two pods get scheduled. Once we submit the scheduler deployment
 and our new scheduler starts running, the `annotation-second-scheduler` pod gets
 scheduled as well.

-Alternatively, one could just look at the "Scheduled" entries in the event logs to
+Alternatively, you can look at the "Scheduled" entries in the event logs to
 verify that the pods were scheduled by the desired schedulers.

 ```shell
@@ -404,7 +404,7 @@ how to [authenticate API servers](/docs/reference/access-authn-authz/extensible-
 A conversion webhook must not mutate anything inside of `metadata` of the converted object
 other than `labels` and `annotations`.
 Attempted changes to `name`, `UID` and `namespace` are rejected and fail the request
-which caused the conversion. All other changes are just ignored.  
+which caused the conversion. All other changes are ignored.  

 ### Deploy the conversion webhook service

@@ -520,7 +520,7 @@ CustomResourceDefinition and migrating your objects from one version to another.
 ### Finalizers

 *Finalizers* allow controllers to implement asynchronous pre-delete hooks.
-Custom objects support finalizers just like built-in objects.
+Custom objects support finalizers similar to built-in objects.

 You can add a finalizer to a custom object like this:

@@ -41,7 +41,7 @@ Alternatively, you can use an existing 3rd party solution, such as [apiserver-bu
 1. Make sure that your extension-apiserver loads those certs from that volume and that they are used in the HTTPS handshake.
 1. Create a Kubernetes service account in your namespace.
 1. Create a Kubernetes cluster role for the operations you want to allow on your resources.
-1. Create a Kubernetes cluster role binding from the service account in your namespace to the cluster role you just created.
+1. Create a Kubernetes cluster role binding from the service account in your namespace to the cluster role you created.
 1. Create a Kubernetes cluster role binding from the service account in your namespace to the `system:auth-delegator` cluster role to delegate auth decisions to the Kubernetes core API server.
 1. Create a Kubernetes role binding from the service account in your namespace to the `extension-apiserver-authentication-reader` role. This allows your extension api-server to access the `extension-apiserver-authentication` configmap.
 1. Create a Kubernetes apiservice. The CA cert above should be base64 encoded, stripped of new lines and used as the spec.caBundle in the apiservice. This should not be namespaced. If using the [kube-aggregator API](https://github.com/kubernetes/kube-aggregator/), only pass in the PEM encoded CA bundle because the base 64 encoding is done for you.
@@ -19,7 +19,7 @@ Here is an overview of the steps in this example:
 1. **Start a message queue service.**  In this example, we use RabbitMQ, but you could use another
   one.  In practice you would set up a message queue service once and reuse it for many jobs.
 1. **Create a queue, and fill it with messages.**  Each message represents one task to be done.  In
-   this example, a message is just an integer that we will do a lengthy computation on.
+   this example, a message is an integer that we will do a lengthy computation on.
 1. **Start a Job that works on tasks from the queue**.  The Job starts several pods.  Each pod takes
   one task from the message queue, processes it, and repeats until the end of the queue is reached.

@@ -141,13 +141,12 @@ root@temp-loe07:/#
 ```

 In the last command, the `amqp-consume` tool takes one message (`-c 1`)
-from the queue, and passes that message to the standard input of an arbitrary command.  In this case, the program `cat` is just printing
-out what it gets on the standard input, and the echo is just to add a carriage
+from the queue, and passes that message to the standard input of an arbitrary command.  In this case, the program `cat` prints out the characters read from standard input, and the echo adds a carriage
 return so the example is readable.

 ## Filling the Queue with tasks

-Now let's fill the queue with some "tasks".  In our example, our tasks are just strings to be
+Now let's fill the queue with some "tasks".  In our example, our tasks are strings to be
 printed.

 In a practice, the content of the messages might be:
@@ -21,7 +21,7 @@ Here is an overview of the steps in this example:
   detect when a finite-length work queue is empty.  In practice you would set up a store such
   as Redis once and reuse it for the work queues of many jobs, and other things.
 1. **Create a queue, and fill it with messages.**  Each message represents one task to be done.  In
-   this example, a message is just an integer that we will do a lengthy computation on.
+   this example, a message is an integer that we will do a lengthy computation on.
 1. **Start a Job that works on tasks from the queue**.  The Job starts several pods.  Each pod takes
   one task from the message queue, processes it, and repeats until the end of the queue is reached.

@@ -55,7 +55,7 @@ You could also download the following files directly:

 ## Filling the Queue with tasks

-Now let's fill the queue with some "tasks".  In our example, our tasks are just strings to be
+Now let's fill the queue with some "tasks".  In our example, our tasks are strings to be
 printed.

 Start a temporary interactive pod for running the Redis CLI.
@@ -25,7 +25,7 @@ You should already know how to [perform a rolling update on a

 ### Step 1: Find the DaemonSet revision you want to roll back to

-You can skip this step if you just want to roll back to the last revision.
+You can skip this step if you only want to roll back to the last revision.

 List all revisions of a DaemonSet:

@@ -111,7 +111,7 @@ kubectl edit ds/fluentd-elasticsearch -n kube-system

 ##### Updating only the container image

-If you just need to update the container image in the DaemonSet template, i.e.
+If you only need to update the container image in the DaemonSet template, i.e.
 `.spec.template.spec.containers[*].image`, use `kubectl set image`:

 ```shell
@@ -167,7 +167,7 @@ If the recent DaemonSet template update is broken, for example, the container is
 crash looping, or the container image doesn't exist (often due to a typo),
 DaemonSet rollout won't progress.

-To fix this, just update the DaemonSet template again. New rollout won't be
+To fix this, update the DaemonSet template again. New rollout won't be
 blocked by previous unhealthy rollouts.

 #### Clock skew
@@ -37,7 +37,7 @@ When the above conditions are true, Kubernetes will expose `amd.com/gpu` or
 `nvidia.com/gpu` as a schedulable resource.

 You can consume these GPUs from your containers by requesting
-`<vendor>.com/gpu` just like you request `cpu` or `memory`.
+`<vendor>.com/gpu` the same way you request `cpu` or `memory`.
 However, there are some limitations in how you specify the resource requirements
 when using GPUs:

@@ -43,8 +43,8 @@ You may need to delete the associated headless service separately after the Stat
 kubectl delete service <service-name>
 ```

-Deleting a StatefulSet through kubectl will scale it down to 0, thereby deleting all pods that are a part of it. 
-If you want to delete just the StatefulSet and not the pods, use `--cascade=false`.
+When deleting a StatefulSet through `kubectl`, the StatefulSet scales down to 0. All Pods that are part of this workload are also deleted. If you want to delete only the StatefulSet and not the Pods, use `--cascade=false`.
+For example:

 ```shell
 kubectl delete -f <file.yaml> --cascade=false
@@ -44,7 +44,7 @@ for StatefulSet Pods. Graceful deletion is safe and will ensure that the Pod
 [shuts down gracefully](/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination)
 before the kubelet deletes the name from the apiserver.

-Kubernetes (versions 1.5 or newer) will not delete Pods just because a Node is unreachable.
+A Pod is not deleted automatically when a node is unreachable.
 The Pods running on an unreachable Node enter the 'Terminating' or 'Unknown' state after a
 [timeout](/docs/concepts/architecture/nodes/#condition).
 Pods may also enter these states when the user attempts graceful deletion of a Pod
@@ -382,7 +382,7 @@ with *external metrics*.

 Using external metrics requires knowledge of your monitoring system; the setup is
 similar to that required when using custom metrics. External metrics allow you to autoscale your cluster
-based on any metric available in your monitoring system. Just provide a `metric` block with a
+based on any metric available in your monitoring system. Provide a `metric` block with a
 `name` and `selector`, as above, and use the `External` metric type instead of `Object`.
 If multiple time series are matched by the `metricSelector`,
 the sum of their values is used by the HorizontalPodAutoscaler.
@@ -23,9 +23,7 @@ Pod Autoscaling does not apply to objects that can't be scaled, for example, Dae

 The Horizontal Pod Autoscaler is implemented as a Kubernetes API resource and a controller.
 The resource determines the behavior of the controller.
-The controller periodically adjusts the number of replicas in a replication controller or deployment
-to match the observed average CPU utilization to the target specified by user.
-
+The controller periodically adjusts the number of replicas in a replication controller or deployment to match the observed metrics such as average CPU utilisation, average memory utilisation or any other custom metric to the target specified by the user.



@@ -162,7 +160,7 @@ can be fetched, scaling is skipped. This means that the HPA is still capable
 of scaling up if one or more metrics give a `desiredReplicas` greater than
 the current value.

-Finally, just before HPA scales the target, the scale recommendation is recorded.  The
+Finally, right before HPA scales the target, the scale recommendation is recorded.  The
 controller considers all recommendations within a configurable window choosing the
 highest recommendation from within that window. This value can be configured using the `--horizontal-pod-autoscaler-downscale-stabilization` flag, which defaults to 5 minutes.
 This means that scaledowns will occur gradually, smoothing out the impact of rapidly
@@ -39,6 +39,7 @@ on general patterns for running stateful applications in Kubernetes.
  [ConfigMaps](/docs/tasks/configure-pod-container/configure-pod-configmap/).
 * Some familiarity with MySQL helps, but this tutorial aims to present
  general patterns that should be useful for other systems.
+* You are using the default namespace or another namespace that does not contain any conflicting objects.



@@ -534,10 +535,9 @@ kubectl delete pvc data-mysql-4
 * Learn more about [debugging a StatefulSet](/docs/tasks/debug-application-cluster/debug-stateful-set/).
 * Learn more about [deleting a StatefulSet](/docs/tasks/run-application/delete-stateful-set/).
 * Learn more about [force deleting StatefulSet Pods](/docs/tasks/run-application/force-delete-stateful-set-pod/).
-* Look in the [Helm Charts repository](https://github.com/kubernetes/charts)
+* Look in the [Helm Charts repository](https://artifacthub.io/)
  for other stateful application examples.




-
@@ -12,10 +12,7 @@ You can use the GCP [Service Catalog Installer](https://github.com/GoogleCloudPl
 tool to easily install or uninstall Service Catalog on your Kubernetes cluster, linking it to
 Google Cloud projects.

-Service Catalog itself can work with any kind of managed service, not just Google Cloud.
-
-
-
+Service Catalog can work with any kind of managed service, not only Google Cloud.

 ## {{% heading "prerequisites" %}}

@@ -17,9 +17,9 @@ and view logs. For more information including a complete list of kubectl operati
 kubectl is installable on a variety of Linux platforms, macOS and Windows. 
 Find your preferred operating system below.

- [Install kubectl on Linux](install-kubectl-linux)
- [Install kubectl on macOS](install-kubectl-macos)
- [Install kubectl on Windows](install-kubectl-windows)
+- [Install kubectl on Linux](/docs/tasks/tools/install-kubectl-linux)
+- [Install kubectl on macOS](/docs/tasks/tools/install-kubectl-macos)
+- [Install kubectl on Windows](/docs/tasks/tools/install-kubectl-windows)

 ## kind

@@ -113,7 +113,7 @@ mind:
    two consecutive lists. **The HTML comment needs to be at the left margin.**
 2.  Numbered lists can have paragraphs or block elements within them.

-    Just indent the content to be the same as the first line of the bullet
+    Indent the content to be the same as the first line of the bullet
    point. **This paragraph and the code block line up with the `N` in
    `Numbered` above.**

@@ -184,7 +184,7 @@ profile k8s-apparmor-example-deny-write flags=(attach_disconnected) {
 ```

 Since we don't know where the Pod will be scheduled, we'll need to load the profile on all our
-nodes. For this example we'll just use SSH to install the profiles, but other approaches are
+nodes. For this example we'll use SSH to install the profiles, but other approaches are
 discussed in [Setting up nodes with profiles](#setting-up-nodes-with-profiles).

 ```shell
@@ -67,8 +67,8 @@ into the cluster.

 For simplicity, [kind](https://kind.sigs.k8s.io/) can be used to create a single
 node cluster with the seccomp profiles loaded. Kind runs Kubernetes in Docker,
-so each node of the cluster is actually just a container. This allows for files
-to be mounted in the filesystem of each container just as one might load files
+so each node of the cluster is a container. This allows for files
+to be mounted in the filesystem of each container similar to loading files
 onto a node.

 {{< codenew file="pods/security/seccomp/kind.yaml" >}}
@@ -46,7 +46,7 @@ This tutorial provides a container image that uses NGINX to echo back all the re
    {{< kat-button >}}

 {{< note >}}
-If you installed minikube locally, run `minikube start`.
+If you installed minikube locally, run `minikube start`. Before you run `minikube dashboard`, you should open a new terminal, start `minikube dashboard` there, and then switch back to the main terminal.
 {{< /note >}}

 2. Open the Kubernetes dashboard in a browser:
@@ -152,7 +152,7 @@ Kubernetes [*Service*](/docs/concepts/services-networking/service/).
    The application code inside the image `k8s.gcr.io/echoserver` only listens on TCP port 8080. If you used
    `kubectl expose` to expose a different port, clients could not connect to that other port.

-2. View the Service you just created:
+2. View the Service you created:

    ```shell
    kubectl get services
@@ -227,7 +227,7 @@ The minikube tool includes a set of built-in {{< glossary_tooltip text="addons"
    metrics-server was successfully enabled
    ```

-3. View the Pod and Service you just created:
+3. View the Pod and Service you created:

    ```shell
    kubectl get pod,svc -n kube-system
@@ -1083,7 +1083,7 @@ above.
 `Parallel` pod management tells the StatefulSet controller to launch or
 terminate all Pods in parallel, and not to wait for Pods to become Running
 and Ready or completely terminated prior to launching or terminating another
-Pod.
+Pod. This option only affects the behavior for scaling operations. Updates are not affected.

 {{< codenew file="application/web/web-parallel.yaml" >}}