Standardize ACME instruction details

Backports #9556

* Standardize ACME instruction details

Our Getting Started guides often include instructions for
configuring Let's Encrypt and ACME before starting
Teleport, but not all of these instructions have the same
level of detail, and some are missing some context around
how Teleport uses ACME and why you need to open port 443 on
your Proxy Service host. This change adds an include that
spells out these instructions and invokes the include in the
appropriate guides.

The intention was to include as much relevant information within
the guides themselves to prevent the reader from having to
navigate to other pages.

Closes #6448

* Respond to PR feedback

- Substitute "proxy" for "node" where it was incorrectly used
- Some small stylistic fixes
- Clarify that "teleport configure" does not write the config
  itself

docs/pages/application-access/getting-started.mdx

@@ -31,32 +31,20 @@ $ docker run -d -p 3000:3000 grafana/grafana
 ```
 
 ## Step 2/3. Install and configure Teleport
+(!docs/pages/includes/permission-warning.mdx!)
 
 Download the latest version of Teleport for your platform from our
 [downloads page](https://goteleport.com/teleport/download).
 
-Teleport requires a valid TLS certificate to operate and can fetch one automatically
-using Let's Encrypt [ACME](https://letsencrypt.org/how-it-works/) protocol.
-
 We will assume that you have configured DNS records for `teleport.example.com`
-and `*.teleport.example.com` to point to the Teleport node.
-
-(!docs/pages/includes/permission-warning.mdx!)
+and `*.teleport.example.com` to point to the Teleport Proxy Service.
 
-Let's generate a Teleport config with ACME enabled:
-
-```code
-$ sudo teleport configure --cluster-name=teleport.example.com --acme [email protected] -o file
-```
+### Configure TLS
+Teleport uses TLS to communicate with clients, and can fetch certificates automatically via Let's Encrypt.
 
-<Admonition
-  type="note"
-  title="Web Proxy Port"
->
-  Teleport uses [TLS-ALPN-01](https://letsencrypt.org/docs/challenge-types/#tls-alpn-01)
-  ACME challenge to validate certificate requests which only works on port `443`. Make sure your Teleport proxy is accessible on port `443` when using ACME for certificate management.
-</Admonition>
+(!docs/pages/includes/acme.mdx!)
 
+### Start Teleport
 Now start Teleport and point it to the application endpoint:
 
 ```code
@@ -69,6 +57,7 @@ $ sudo teleport start \
 Make sure to update `--app-name` and `--app-uri` accordingly if you're using
 your own web application.
 
+### Create a user
 Next, let's create a user to access the application we've just connected. Teleport has a built-in role called `access` that allows users to access cluster resources. Create a local user assigned this role:
 
 ```code

docs/pages/application-access/guides/connecting-apps.mdx

@@ -59,31 +59,13 @@ In our example:
 - `teleport.example.com` will host the Access Plane.
 - `*.teleport.example.com` will host all of the applications e.g. `grafana.teleport.example.com`.
 
-Teleport can obtain a certificate automatically from Let's Encrypt using
-[ACME](https://letsencrypt.org/how-it-works/) protocol.
-
-Enable ACME in your proxy config:
-
-```yaml
-proxy_service:
-  enabled: "yes"
-  web_listen_addr: "0.0.0.0:443"
-  public_addr: "teleport.example.com:443"
-  acme:
-    enabled: "yes"
-    email: [email protected]
-```
-
-<Admonition
-  type="note"
-  title="Web Proxy Port"
->
-  Teleport uses [TLS-ALPN-01](https://letsencrypt.org/docs/challenge-types/#tls-alpn-01)
-  ACME challenge to validate certificate requests which only works on port `443`.  Make sure your Teleport proxy is accessible on port `443` when using ACME for certificate management.
-</Admonition>
-
-Alternatively, if you have obtained certificate/key pairs for your domain
-(e.g. using [certbot](https://certbot.eff.org/)), they can be provided directly
+You can either configure Teleport to obtain a TLS certificate via Let's Encrypt or use an existing certificate and private key (e.g. using [certbot](https://certbot.eff.org/)).
+<Tabs>
+<TabItem label="Let's Encrypt">
+(!docs/pages/includes/acme.mdx!)
+</TabItem>
+<TabItem label="Existing Credentials">
+If you have obtained certificate/key pairs for your domain they can be provided directly
 to the proxy service:
 
 ```yaml
@@ -97,6 +79,8 @@ proxy_service:
   - key_file: "/etc/letsencrypt/live/*.teleport.example.com/privkey.pem"
     cert_file: "/etc/letsencrypt/live/*.teleport.example.com/fullchain.pem"
 ```
+</TabItem>
+</Tabs>
 
 ### Create a user
 

docs/pages/database-access/getting-started.mdx

@@ -14,7 +14,7 @@ Here's an overview of what we will do:
 2. Download and install Teleport (=teleport.version=) and connect it to the Aurora database.
 3. Connect to the Aurora database via Teleport.
 
-## Step 1/3. Setup Aurora
+## Step 1/3. Set up Aurora
 
 In order to allow Teleport connections to an Aurora instance, it needs to support
 IAM authentication.
@@ -73,33 +73,22 @@ GRANT rds_iam TO alice;
 For more information about connecting to the PostgreSQL instance directly,
 see Amazon [documentation](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ConnectToPostgreSQLInstance.html).
 
-## Step 2/3. Setup Teleport
+## Step 2/3. Set up Teleport
 
 Teleport Database Access is available starting from `6.0.0` release.
 
 Download the appropriate version of Teleport for your platform from
 our [downloads page](https://goteleport.com/teleport/download).
 
-Teleport requires a valid TLS certificate to operate and can fetch one automatically
-using Let's Encrypt [ACME](https://letsencrypt.org/how-it-works/) protocol.
 
-We will assume that you have configured DNS records for `teleport.example.com` and
-`*.teleport.example.com` to point to the node where you're launching Teleport.
+### Configure TLS
 
-Let's generate a Teleport config with ACME enabled:
+Teleport requires a valid TLS certificate to operate and can fetch one automatically
+using Let's Encrypt.
 
-```code
-$ teleport configure --cluster-name=teleport.example.com --acme [email protected] > /tmp/teleport.yaml
-```
+(!docs/pages/includes/acme.mdx!)
 
-<Admonition
-  type="warning"
-  title="Web Proxy Port"
->
-  Teleport's ACME protocol integration currently requires web proxy to run on
-  port 443 so open /tmp/teleport.yaml and update `proxy_service.web_listen_addr`
-  and `proxy_service.public_addr` to use port 443 instead of the default 3080.
-</Admonition>
+### Start Teleport
 
 Now start Teleport and point it to your Aurora database instance. Make sure to
 update the database endpoint and region appropriately.
@@ -118,9 +107,11 @@ $ sudo teleport start --config=/tmp/teleport.yaml \
   title="AWS Credentials"
 >
   The node that connects to the database should have AWS credentials configured
-  with the policy from [step 1](#step-13-setup-aurora).
+  with the policy from [step 1](#step-13-set-up-aurora).
 </Admonition>
 
+### Create a user and role
+
 Create the role that will allow a user to connect to any database using any
 database account:
 

docs/pages/getting-started/linux-server.mdx

@@ -61,9 +61,49 @@ Start Teleport:
 $ sudo teleport start
 ```
 
-You can access Teleport's Web UI on port `443`.
+<Tabs>
+  <TabItem label="Public internet deployment with Let's Encrypt">
+  (!docs/pages/includes/acme.mdx!)
+
+  </TabItem>
+
+  <TabItem label="Private net deployment">
+  On your Teleport host, place a valid private key and a certificate chain in `/var/lib/teleport/privkey.pem`
+  and `/var/lib/teleport/fullchain.pem` respectively.
+
+  The leaf certificate must have a subject that corresponds to the domain of your Teleport host, e.g., `*.teleport.example.com`.
+
+  Configure Teleport, changing the values of the `--cluster-name` and `--public-addr` flags to match the domain name of your Teleport host.
+
+  ```code
+  $ sudo teleport configure -o file \
+      --cluster-name=tele.example.com \
+      --public-addr=tele.example.com:443 \
+      --cert-file=/var/lib/teleport/fullchain.pem \
+      --key-file=/var/lib/teleport/privkey.pem
+  ```
+  </TabItem>
+
+</Tabs>
+
+
+## Start Teleport
+
+<Tabs>
+  <TabItem label="Package manager RPM/DEB">
+    ```code
+    $ sudo systemctl start teleport
+    ```
+  </TabItem>
+
+  <TabItem label="Source or custom install">
+    ```code
+    $ sudo teleport start
+    ```
+  </TabItem>
+</Tabs>
 
-Replace `tele.example.com` with your domain: `https://tele.example.com/`.
+You can access Teleport's Web UI via HTTPS at the domain you created earlier.
 
 ## Step 2/4. Create a Teleport user and set up two-factor authentication
 

docs/pages/includes/acme.mdx

@@ -0,0 +1,23 @@
+Let's Encrypt verifies that you control the domain name of your Teleport deployment by communicating with the HTTPS server listening on port 443 of your Teleport Proxy Service. 
+
+You can configure the Teleport Proxy service to complete the Let's Encrypt verification process when it starts up.
+
+Run the following `teleport configure` command, where `tele.example.com` is the domain name of your Teleport cluster and `[email protected]` is an email address used for notifications (you can use any domain):
+
+```code
+teleport configure --acme [email protected] --cluster-name=tele.example.com > /etc/teleport.yaml
+```
+
+The `--acme`, `--acme-email`, and `--cluster-name` flags will add the following settings to your Teleport configuration file:
+
+```yaml
+proxy_service:
+  enabled: "yes"
+  web_listen_addr: :443
+  public_addr: tele.example.com:443
+  acme:
+    enabled: "yes"
+    email: [email protected]
+```
+
+Port 443 on your Teleport Proxy Service host must allow traffic from all sources.

docs/pages/includes/database-access/start-auth-proxy.mdx

@@ -6,7 +6,7 @@ issue a TLS certificate for the Teleport Proxy host's domain, the ACME protocol
 must verify that an HTTPS server is reachable on port 443 of the host.  
 
 We will assume that you have configured DNS records for `teleport.example.com`
-and `*.teleport.example.com` to point to your Teleport node.
+and `*.teleport.example.com` to point to your Teleport Node.
 
 <Admonition type="note" title="Web Proxy Port">
 To support the ACME protocol, Teleport Proxy must listen on port 443, rather
@@ -17,13 +17,13 @@ Download the latest version of Teleport for your platform from our
 [downloads page](https://goteleport.com/teleport/download) and follow the
 installation [instructions](../../installation.mdx).
 
-Generate a Teleport configuration file with ACME enabled:
+Teleport requires a valid TLS certificate to operate and can fetch one automatically
+using Let's Encrypt. 
+We will assume that you have configured DNS records for `teleport.example.com` and `*.teleport.example.com` to point to the Teleport Node.
 
-```code
-$ teleport configure --cluster-name=teleport.example.com --acme [email protected] -o file
-```
+(!docs/pages/includes/acme.mdx!)
 
-Start the Teleport Auth and Proxy services:
+Next, start the Teleport Auth and Proxy Services:
 
 ```code
 $ sudo teleport start

docs/pages/server-access/getting-started.mdx

@@ -70,15 +70,9 @@ This guide introduces some of these common scenarios and how to interact with Te
 
 3. Configure Teleport on the *Bastion Host*.
 
-   Teleport will now automatically acquire an X.509 certificate using the ACME protocol.
+   Teleport uses TLS to communicate with clients, and can fetch certificates automatically via Let's Encrypt.
 
-   ```code
-   # Configure Teleport with TLS certs
-   $ sudo teleport configure \
-     --acme [email protected] \
-     --cluster-name=tele.example.com \
-     -o file
-   ```
+   (!docs/pages/includes/acme.mdx!)
 
    Run the command above on `tele.example.com`.