Merge branch 'docs-aqualls-cluster-note-itis' into 'master'

Begin revising applications page for tone/style

See merge request gitlab-org/gitlab!43154

doc/user/clusters/applications.md

@@ -6,37 +6,29 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 # GitLab Managed Apps
 
-GitLab provides **GitLab Managed Apps**, a one-click install for various applications which can
-be added directly to your configured cluster.
-
-These applications are needed for [Review Apps](../../ci/review_apps/index.md)
-and [deployments](../../ci/environments/index.md) when using [Auto DevOps](../../topics/autodevops/index.md).
-
-You can install them after you
-[create a cluster](../project/clusters/add_remove_clusters.md).
+GitLab provides **GitLab Managed Apps**, a one-click install for various
+applications which can be added directly to your configured cluster. These
+applications are needed for [Review Apps](../../ci/review_apps/index.md) and
+[deployments](../../ci/environments/index.md) when using [Auto DevOps](../../topics/autodevops/index.md).
+You can install them after you [create a cluster](../project/clusters/add_remove_clusters.md).
 
 ## Installing applications
 
-Applications managed by GitLab will be installed onto the `gitlab-managed-apps` namespace.
-
-This namespace:
+Applications managed by GitLab are installed onto the `gitlab-managed-apps`
+namespace. This namespace:
 
 - Is different from the namespace used for project deployments.
 - Is created once.
 - Has a non-configurable name.
 
-To see a list of available applications to install. For a:
+To view a list of available applications to install for a:
 
 - [Project-level cluster](../project/clusters/index.md), navigate to your project's
   **Operations > Kubernetes**.
 - [Group-level cluster](../group/clusters/index.md), navigate to your group's
   **Kubernetes** page.
 
-NOTE: **Note:**
-As of GitLab 11.6, Helm will be upgraded to the latest version supported
-by GitLab before installing any of the applications.
-
-The following applications can be installed:
+You can install the following applications:
 
 - [Helm](#helm)
 - [Ingress](#ingress)
@@ -49,10 +41,9 @@ The following applications can be installed:
 - [Elastic Stack](#elastic-stack)
 - [Fluentd](#fluentd)
 
-With the exception of Knative, the applications will be installed in a dedicated
+With the exception of Knative, the applications are installed in a dedicated
 namespace called `gitlab-managed-apps`.
 
-NOTE: **Note:**
 Some applications are installable only for a project-level cluster.
 Support for installing these applications in a group-level cluster is
 planned for future releases.
@@ -65,6 +56,9 @@ you should be careful as GitLab cannot detect it. In this case, installing
 Helm via the applications will result in the cluster having it twice, which
 can lead to confusion during deployments.
 
+In GitLab versions 11.6 and greater, Helm is upgraded to the latest version
+supported by GitLab before installing any of the applications.
+
 ### Helm
 
 > - Introduced in GitLab 10.2 for project-level clusters.
@@ -81,7 +75,6 @@ applications. Prior to [GitLab 13.2](https://gitlab.com/gitlab-org/gitlab/-/issu
 GitLab used an in-cluster Tiller server in the `gitlab-managed-apps`
 namespace. This server can now be safely removed.
 
-NOTE: **Note:**
 GitLab's Helm integration does not support installing applications behind a proxy,
 but a [workaround](../../topics/autodevops/index.md#install-applications-behind-a-proxy)
 is available.
@@ -90,26 +83,25 @@ is available.
 
 > Introduced in GitLab 11.6 for project- and group-level clusters.
 
-[cert-manager](https://cert-manager.io/docs/) is a native
-Kubernetes certificate management controller that helps with issuing
-certificates. Installing cert-manager on your cluster will issue a
-certificate by [Let's Encrypt](https://letsencrypt.org/) and ensure that
-certificates are valid and up-to-date.
+[cert-manager](https://cert-manager.io/docs/) is a native Kubernetes certificate
+management controller that helps with issuing certificates. Installing
+cert-manager on your cluster issues a certificate by [Let's Encrypt](https://letsencrypt.org/)
+and ensures that certificates are valid and up-to-date.
 
 The chart used to install this application depends on the version of GitLab used. In:
 
-- GitLab 12.3 and newer, the [jetstack/cert-manager](https://github.com/jetstack/cert-manager)
+- GitLab 12.3 and newer, the [`jetstack/cert-manager`](https://github.com/jetstack/cert-manager)
   chart is used with a [`values.yaml`](https://gitlab.com/gitlab-org/gitlab/blob/master/vendor/cert_manager/values.yaml)
   file.
-- GitLab 12.2 and older, the [stable/cert-manager](https://github.com/helm/charts/tree/master/stable/cert-manager)
+- GitLab 12.2 and older, the [`stable/cert-manager`](https://gi2wthub.com/helm/charts/tree/master/stable/cert-manager)
   chart was used.
 
-If you have installed cert-manager prior to GitLab 12.3, Let's Encrypt will
-[block requests from older versions of cert-manager](https://community.letsencrypt.org/t/blocking-old-cert-manager-versions/98753).
-
-To resolve this:
+If you installed cert-manager prior to GitLab 12.3, Let's Encrypt
+[blocks requests](https://community.letsencrypt.org/t/blocking-old-cert-manager-versions/98753)
+from older versions of `cert-manager`. To resolve this:
 
-1. Uninstall cert-manager (consider [backing up any additional configuration](https://cert-manager.io/docs/tutorials/backup/)).
+1. [Back up any additional configuration](https://cert-manager.io/docs/tutorials/backup/).
+1. Uninstall cert-manager.
 1. Install cert-manager again.
 
 ### GitLab Runner
@@ -117,26 +109,21 @@ To resolve this:
 > - Introduced in GitLab 10.6 for project-level clusters.
 > - Introduced in GitLab 11.10 for group-level clusters.
 
-[GitLab Runner](https://docs.gitlab.com/runner/) is the open source
-project that is used to run your jobs and send the results back to
-GitLab. It is used in conjunction with [GitLab
-CI/CD](../../ci/README.md), the open-source continuous integration
-service included with GitLab that coordinates the jobs.
-
-If the project is on GitLab.com, shared runners are available
-(the first 2000 minutes are free, you can
-[buy more later](../../subscriptions/gitlab_com/index.md#purchase-additional-ci-minutes))
-and you do not have to deploy one if they are enough for your needs. If a
-project-specific runner is desired, or there are no shared runners, it is easy
-to deploy one.
-
-Note that the deployed runner will be set as **privileged**, which means it will essentially
-have root access to the underlying machine. This is required to build Docker images,
-so it is the default. Make sure you read the
-[security implications](../project/clusters/index.md#security-implications)
+[GitLab Runner](https://docs.gitlab.com/runner/) is the open source project that
+is used to run your jobs and send the results back to GitLab. It's used in
+conjunction with [GitLab CI/CD](../../ci/README.md), the open-source continuous
+integration service included with GitLab that coordinates the jobs.
+
+If the project is on GitLab.com, [shared runners](../gitlab_com/index.md#shared-runners)
+are available, and you do not have to deploy one if they are enough for your
+needs. If a project-specific runner is desired, or there are no shared runners,
+you can deploy one.
+
+The deployed runner is set as **privileged**. Root access to the underlying
+server is required to build Docker images, so it is the default. Be sure to read
+the [security implications](../project/clusters/index.md#security-implications)
 before deploying one.
 
-NOTE: **Note:**
 The [`runner/gitlab-runner`](https://gitlab.com/gitlab-org/charts/gitlab-runner)
 chart is used to install this application, using
 [a preconfigured `values.yaml`](https://gitlab.com/gitlab-org/charts/gitlab-runner/-/blob/master/values.yaml)