Move GitLab Managed Apps to own page

So we can add detailed information, and also point to SSOT

3 files changed, 271 insertions, 132 deletions

diff --git a/doc/user/clusters/applications.md b/doc/user/clusters/applications.md
new file mode 100644
index 00000000000..97abe99fe62
--- /dev/null
+++ b/doc/user/clusters/applications.md
@@ -0,0 +1,263 @@
+# 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.md) when using [Auto DevOps](../../topics/autodevops/index.md).
+You can install them after you
+[create a cluster](../project/clusters/index.md#adding-and-creating-a-new-gke-cluster-via-gitlab).
+
+## Installing applications
+
+Applications managed by GitLab will be 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:
+
+1. For a:
+    - Project-level cluster, navigate to your project's **Operations > Kubernetes**.
+    - Group-level cluster, navigate to your group's **Kubernetes** page.
+
+Install Helm first as it's used to install other applications.
+
+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:
+
+- [Helm](#helm)
+- [Ingress](#ingress)
+- [Cert-Manager](#cert-manager)
+- [Prometheus](#prometheus)
+- [GitLab Runner](#gitlab-runner)
+- [JupyterHub](#jupyterhub)
+- [Knative](#knative)
+
+With the exception of Knative, the applications will be 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.
+For updates, see [the issue tracking
+progress](https://gitlab.com/gitlab-org/gitlab-ce/issues/51989).
+
+CAUTION: **Caution:**
+If you have an existing Kubernetes cluster with Helm already installed,
+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.
+
+### Helm
+
+> - Available for project-level clusters since GitLab 10.2.
+> - Available for group-level clusters since GitLab 11.6.
+
+[Helm](https://docs.helm.sh/) is a package manager for Kubernetes and is
+required to install all the other applications. It is installed in its
+own pod inside the cluster which can run the `helm` CLI in a safe
+environment.
+
+### Cert-Manager
+
+> - Available for project-level clusters since GitLab 11.6.
+> - Available for group-level clusters since GitLab 11.6.
+
+[Cert-Manager](https://docs.cert-manager.io/en/latest/) 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.
+
+NOTE: **Note:**
+The
+[stable/cert-manager](https://github.com/helm/charts/tree/master/stable/cert-manager)
+chart is used to install this application with a
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/cert_manager/values.yaml)
+file.
+
+### GitLab Runner
+
+> - Available for project-level clusters since GitLab 10.6.
+> - Available for group-level clusters since GitLab 11.10.
+
+[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. When installing
+the GitLab Runner via the applications, it will run in **privileged
+mode** by default. Make sure you read the [security
+implications](../project/clusters/index.md/#security-implications) before doing so.
+
+NOTE: **Note:**
+The
+[runner/gitlab-runner](https://gitlab.com/charts/gitlab-runner)
+chart is used to install this application with a
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/runner/values.yaml)
+file.
+
+### Ingress
+
+> - Available for project-level clusters since GitLab 10.2.
+> - Available for group-level clusters since GitLab 11.6.
+
+[Ingress](https://kubernetes.github.io/ingress-nginx/) can provide load
+balancing, SSL termination, and name-based virtual hosting. It acts as a
+web proxy for your applications and is useful if you want to use [Auto
+DevOps] or deploy your own web apps.
+
+NOTE: **Note:**
+The
+[stable/nginx-ingress](https://github.com/helm/charts/tree/master/stable/nginx-ingress)
+chart is used to install this application with a
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/ingress/values.yaml)
+file.
+
+### JupyterHub
+
+> Available for project-level clusters since GitLab 11.0.
+
+[JupyterHub](https://jupyterhub.readthedocs.io/en/stable/) is a
+multi-user service for managing notebooks across a team. [Jupyter
+Notebooks](https://jupyter-notebook.readthedocs.io/en/latest/) provide a
+web-based interactive programming environment used for data analysis,
+visualization, and machine learning.
+
+Authentication will be enabled only for [project
+members](../project/members/index.md) with [Developer or
+higher](../permissions.md) access to the project.
+
+We use a [custom Jupyter
+image](https://gitlab.com/gitlab-org/jupyterhub-user-image/blob/master/Dockerfile)
+that installs additional useful packages on top of the base Jupyter. You
+will also see ready-to-use DevOps Runbooks built with Nurtch's [Rubix library](https://github.com/amit1rrr/rubix).
+
+More information on
+creating executable runbooks can be found in [our Nurtch
+documentation](../project/clusters/runbooks/index.md#nurtch-executable-runbooks). Note that
+Ingress must be installed and have an IP address assigned before
+JupyterHub can be installed.
+
+NOTE: **Note:**
+The
+[jupyter/jupyterhub](https://jupyterhub.github.io/helm-chart/)
+chart is used to install this application with a
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/jupyter/values.yaml)
+file.
+
+### Knative
+
+> Available for project-level clusters since GitLab 11.5.
+
+[Knative](https://cloud.google.com/knative) provides a platform to
+create, deploy, and manage serverless workloads from a Kubernetes
+cluster. It is used in conjunction with, and includes
+[Istio](https://istio.io) to provide an external IP address for all
+programs hosted by Knative.
+
+You will be prompted to enter a wildcard
+domain where your applications will be exposed. Configure your DNS
+server to use the external IP address for that domain. For any
+application created and installed, they will be accessible as
+`<program_name>.<kubernetes_namespace>.<domain_name>`. This will require
+your kubernetes cluster to have [RBAC
+enabled](../project/clusters/index.md#rbac-cluster-resources).
+
+NOTE: **Note:**
+The
+[knative/knative](https://storage.googleapis.com/triggermesh-charts)
+chart is used to install this application.
+
+### Prometheus
+
+> - Available for project-level clusters since GitLab 10.4.
+> - Available for group-level clusters since GitLab 11.11.
+
+[Prometheus](https://prometheus.io/docs/introduction/overview/) is an
+open-source monitoring and alerting system useful to supervise your
+deployed applications.
+
+NOTE: **Note:**
+The
+[stable/prometheus](https://github.com/helm/charts/tree/master/stable/prometheus)
+chart is used to install this application with a
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/prometheus/values.yaml)
+file.
+
+## Upgrading applications
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24789)
+in GitLab 11.8.
+
+The applications below can be upgraded.
+
+| Application | GitLab version |
+| ----------- | -------------- |
+| Runner  | 11.8+          |
+
+To upgrade an application:
+
+1. For a:
+    - Project-level cluster, navigate to your project's **Operations > Kubernetes**.
+    - Group-level cluster, navigate to your group's **Kubernetes** page.
+1. Select your cluster.
+1. If an upgrade is available, the **Upgrade** button is displayed. Click the button to upgrade.
+
+NOTE: **Note:**
+Upgrades will reset values back to the values built into the `runner`
+chart plus the values set by
+[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/runner/values.yaml)
+
+## Uninstalling applications
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/60665) in
+> GitLab 11.11.
+
+The applications below can be uninstalled.
+
+| Application | GitLab version | Notes |
+| ----------- | -------------- | ----- |
+| Prometheus  | 11.11+         | All data will be deleted and cannot be restored. |
+
+To uninstall an application:
+
+1. For a:
+    - Project-level cluster, navigate to your project's **Operations > Kubernetes**.
+    - Group-level cluster, navigate to your group's **Kubernetes** page.
+1. Select your cluster.
+1. Click the **Uninstall** button for the application.
+
+Support for uninstalling all applications is planned for progressive rollout.
+To follow progress, see [the relevant
+epic](https://gitlab.com/groups/gitlab-org/-/epics/1201).
+
+## Troubleshooting applications
+
+Applications can fail with the following error:
+
+```text
+Error: remote error: tls: bad certificate
+```
+
+To avoid installation errors:
+
+- Before starting the installation of applications, make sure that time is synchronized
+  between your GitLab server and your Kubernetes cluster.
+- Ensure certificates are not out of sync. When installing applications, GitLab expects a new cluster with no previous installation of Helm.
+
+  You can confirm that the certificates match via `kubectl`:
+
+  ```sh
+  kubectl get configmaps/values-content-configuration-ingress -n gitlab-managed-apps -o \
+  "jsonpath={.data['cert\.pem']}" | base64 -d > a.pem
+  kubectl get secrets/tiller-secret -n gitlab-managed-apps -o "jsonpath={.data['ca\.crt']}" | base64 -d > b.pem
+  diff a.pem b.pem
+  ```
+
diff --git a/doc/user/group/clusters/index.md b/doc/user/group/clusters/index.md
index ff6aa4f5930..8458b4f5de3 100644
--- a/doc/user/group/clusters/index.md
+++ b/doc/user/group/clusters/index.md
@@ -12,33 +12,10 @@ your group, enabling you to use the same cluster across multiple projects.
 
 ## Installing applications
 
-GitLab provides a one-click install for various applications that can be
-added directly to your cluster.
-
-NOTE: **Note:**
-Applications will be installed in a dedicated namespace called
-`gitlab-managed-apps`. If you have added an existing Kubernetes cluster
-with Tiller already installed, you should be careful as GitLab cannot
-detect it. In this event, installing Tiller via the applications will
-result in the cluster having it twice. This can lead to confusion during
-deployments.
-
-| Application                                                                | GitLab version | Description | Helm Chart |
-| -----------                                                                | -------------- | ----------- | ---------- |
-| [Helm Tiller](https://docs.helm.sh)                                        | 11.6+          | Helm is a package manager for Kubernetes and is required to install all the other applications. It is installed in its own pod inside the cluster which can run the `helm` CLI in a safe environment. | n/a |
-| [Ingress](https://kubernetes.io/docs/concepts/services-networking/ingress) | 11.6+          | Ingress can provide load balancing, SSL termination, and name-based virtual hosting. It acts as a web proxy for your applications and is useful if you want to use [Auto DevOps](../../../topics/autodevops/index.md) or deploy your own web apps. | [stable/nginx-ingress](https://github.com/helm/charts/tree/master/stable/nginx-ingress) |
-| [Cert-Manager](https://docs.cert-manager.io/en/latest/) | 11.6+ | Cert-Manager 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. | [stable/cert-manager](https://github.com/helm/charts/tree/master/stable/cert-manager) |
-| [Prometheus](https://prometheus.io/docs/introduction/overview/) | 11.11+ | Prometheus is an open-source monitoring and alerting system useful to supervise your deployed applications. | [stable/prometheus](https://github.com/helm/charts/tree/master/stable/prometheus) |
-| [GitLab Runner](https://docs.gitlab.com/runner/) | 11.10+ | GitLab 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. When installing the GitLab Runner via the applications, it will run in **privileged mode** by default. Make sure you read the [security implications](../../project/clusters/index.md#security-implications) before doing so. | [runner/gitlab-runner](https://gitlab.com/charts/gitlab-runner) |
-
-NOTE: **Note:**
-Some [cluster
-applications](../../project/clusters/index.md#installing-applications)
-are installable only for a project-level cluster. Support for installing these
-applications in a group-level cluster is planned for future releases. For updates, see:
-
-- Support installing [JupyterHub in group-level
-  clusters](https://gitlab.com/gitlab-org/gitlab-ce/issues/51989)
+GitLab can install and manage some applications in your group-level
+cluster. For more information on installing, upgrading, uninstalling,
+and troubleshooting applications for your group cluster, see
+[Gitlab Managed Apps](../../clusters/applications.md).
 
 ## RBAC compatibility
 
diff --git a/doc/user/project/clusters/index.md b/doc/user/project/clusters/index.md
index bc4d732a405..e38e4059117 100644
--- a/doc/user/project/clusters/index.md
+++ b/doc/user/project/clusters/index.md
@@ -347,111 +347,10 @@ install it manually.
 
 ## Installing applications
 
-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.md) when using [Auto DevOps](../../../topics/autodevops/index.md).
-You can install them after you
-[create a cluster](#adding-and-creating-a-new-gke-cluster-via-gitlab).
-
-Applications managed by GitLab will be installed onto the `gitlab-managed-apps` namespace. This differrent
-from the namespace used for project deployments. It is only created once and its name is not configurable.
-
-To see a list of available applications to install:
-
-1. Navigate to your project's **Operations > Kubernetes**.
-1. Select your cluster.
-
-Install Helm first as it's used to install other applications.
-
-NOTE: **Note:**
-As of GitLab 11.6, Helm will be upgraded to the latest version supported
-by GitLab before installing any of the applications.
-
-| Application | GitLab version | Description | Helm Chart |
-| ----------- | :------------: | ----------- | --------------- |
-| [Helm](https://docs.helm.sh/) | 10.2+ | Helm is a package manager for Kubernetes and is required to install all the other applications. It is installed in its own pod inside the cluster which can run the `helm` CLI in a safe environment. | n/a |
-| [Ingress](https://kubernetes.io/docs/concepts/services-networking/ingress/) | 10.2+ | Ingress can provide load balancing, SSL termination, and name-based virtual hosting. It acts as a web proxy for your applications and is useful if you want to use [Auto DevOps] or deploy your own web apps. | [stable/nginx-ingress](https://github.com/helm/charts/tree/master/stable/nginx-ingress) |
-| [Cert-Manager](https://docs.cert-manager.io/en/latest/) | 11.6+ | Cert-Manager 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. | [stable/cert-manager](https://github.com/helm/charts/tree/master/stable/cert-manager) |
-| [Prometheus](https://prometheus.io/docs/introduction/overview/) | 10.4+ | Prometheus is an open-source monitoring and alerting system useful to supervise your deployed applications. | [stable/prometheus](https://github.com/helm/charts/tree/master/stable/prometheus) |
-| [GitLab Runner](https://docs.gitlab.com/runner/) | 10.6+ | GitLab 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. When installing the GitLab Runner via the applications, it will run in **privileged mode** by default. Make sure you read the [security implications](#security-implications) before doing so. | [runner/gitlab-runner](https://gitlab.com/charts/gitlab-runner) |
-| [JupyterHub](http://jupyter.org/) | 11.0+ | [JupyterHub](https://jupyterhub.readthedocs.io/en/stable/) is a multi-user service for managing notebooks across a team. [Jupyter Notebooks](https://jupyter-notebook.readthedocs.io/en/latest/) provide a web-based interactive programming environment used for data analysis, visualization, and machine learning. We use a [custom Jupyter image](https://gitlab.com/gitlab-org/jupyterhub-user-image/blob/master/Dockerfile) that installs additional useful packages on top of the base Jupyter. Authentication will be enabled only for [project members](../members/index.md) with [Developer or higher](../../permissions.md) access to the project. You will also see ready-to-use DevOps Runbooks built with Nurtch's [Rubix library](https://github.com/amit1rrr/rubix). More information on creating executable runbooks can be found in [our Nurtch documentation](runbooks/index.md#nurtch-executable-runbooks). Note that Ingress must be installed and have an IP address assigned before JupyterHub can be installed. | [jupyter/jupyterhub](https://jupyterhub.github.io/helm-chart/) |
-| [Knative](https://cloud.google.com/knative) | 11.5+ | Knative provides a platform to create, deploy, and manage serverless workloads from a Kubernetes cluster. It is used in conjunction with, and includes [Istio](https://istio.io) to provide an external IP address for all programs hosted by Knative. You will be prompted to enter a wildcard domain where your applications will be exposed. Configure your DNS server to use the external IP address for that domain. For any application created and installed, they will be accessible as `<program_name>.<kubernetes_namespace>.<domain_name>`. This will require your kubernetes cluster to have [RBAC enabled](#rbac-cluster-resources). | [knative/knative](https://storage.googleapis.com/triggermesh-charts)
-
-With the exception of Knative, the applications will be installed in a dedicated
-namespace called `gitlab-managed-apps`.
-
-CAUTION: **Caution:**
-If you have an existing Kubernetes cluster with Helm already installed,
-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.
-
-### Upgrading applications
-
-> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24789)
-in GitLab 11.8.
-
-Users can perform a one-click upgrade for the GitLab Runner application,
-when there is an upgrade available.
-
-To upgrade the GitLab Runner application:
-
-1. Navigate to your project's **Operations > Kubernetes**.
-1. Select your cluster.
-1. Click the **Upgrade** button for the Runnner application.
-
-The **Upgrade** button will not be shown if there is no upgrade
-available.
-
-NOTE: **Note:**
-Upgrades will reset values back to the values built into the `runner`
-chart plus the values set by
-[`values.yaml`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/vendor/runner/values.yaml)
-
-### Uninstalling applications
-
-> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/60665) in
-> GitLab 11.11.
-
-The applications below can be uninstalled.
-
-| Application | GitLab version | Notes |
-| ----------- | -------------- | ----- |
-| Prometheus  | 11.11+         | All data will be deleted and cannot be restored. |
-
-To uninstall an application:
-
-1. Navigate to your project's **Operations > Kubernetes**.
-1. Select your cluster.
-1. Click the **Uninstall** button for the application.
-
-Support for uninstalling all applications is planned for progressive rollout.
-To follow progress, see [the relevant
-epic](https://gitlab.com/groups/gitlab-org/-/epics/1201).
-
-### Troubleshooting applications
-
-Applications can fail with the following error:
-
-```text
-Error: remote error: tls: bad certificate
-```
-
-To avoid installation errors:
-
-- Before starting the installation of applications, make sure that time is synchronized
-  between your GitLab server and your Kubernetes cluster.
-- Ensure certificates are not out of sync.  When installing applications, GitLab expects a new cluster with no previous installation of Helm.
-
-  You can confirm that the certificates match via `kubectl`:
-
-  ```sh
-  kubectl get configmaps/values-content-configuration-ingress -n gitlab-managed-apps -o \
-  "jsonpath={.data['cert\.pem']}" | base64 -d > a.pem
-  kubectl get secrets/tiller-secret -n gitlab-managed-apps -o "jsonpath={.data['ca\.crt']}" | base64 -d > b.pem
-  diff a.pem b.pem
-  ```
+GitLab can install and manage some applications in your project-level
+cluster. For more information on installing, upgrading, uninstalling,
+and troubleshooting applications for your project cluster, see
+[Gitlab Managed Apps](../../clusters/applications.md).
 
 ## Getting the external endpoint