Clarify UI CI variables are'nt available to services

doc/ci/services/gitlab.md

@@ -24,10 +24,9 @@ tests access to the GitLab API.
      GITLAB_ROOT_PASSWORD: "password"  # to access the api with user root:password
    ```
 
-1. To set values for the `GITLAB_HTTPS` and `GITLAB_ROOT_PASSWORD`,
-   [assign them to a variable in the user interface](../variables/index.md#add-a-cicd-variable-to-a-project).
-   Then assign that variable to the corresponding variable in your
-   `.gitlab-ci.yml` file.
+NOTE:
+Variables set in the GitLab UI are not passed down to the service containers.
+[Learn more](../variables/index.md#).
 
 Then, commands in `script:` sections in your `.gitlab-ci.yml` file can access the API at `http://gitlab/api/v4`.
 

doc/ci/services/mysql.md

@@ -16,11 +16,9 @@ If you want to use a MySQL container, you can use [GitLab Runner](../runners/ind
 
 This example shows you how to set a username and password that GitLab uses to access the MySQL container. If you do not set a username and password, you must use `root`.
 
-1. [Create CI/CD variables](../variables/index.md#custom-cicd-variables) for your
-   MySQL database and password by going to **Settings > CI/CD**, expanding **Variables**,
-   and clicking **Add Variable**.
-
-   This example uses `$MYSQL_DB` and `$MYSQL_PASS` as the keys.
+NOTE:
+Variables set in the GitLab UI are not passed down to the service containers.
+[Learn more](../variables/index.md).
 
 1. To specify a MySQL image, add the following to your `.gitlab-ci.yml` file:
 
@@ -39,8 +37,8 @@ This example shows you how to set a username and password that GitLab uses to ac
    ```yaml
    variables:
      # Configure mysql environment variables (https://hub.docker.com/_/mysql/)
-     MYSQL_DATABASE: $MYSQL_DB
-     MYSQL_ROOT_PASSWORD: $MYSQL_PASS
+     MYSQL_DATABASE: $MYSQL_DATABASE
+     MYSQL_ROOT_PASSWORD: $MYSQL_ROOT_PASSWORD
    ```
 
    The MySQL container uses `MYSQL_DATABASE` and `MYSQL_ROOT_PASSWORD` to connect to the database.

doc/ci/services/postgres.md

@@ -16,6 +16,10 @@ do this with the Docker and Shell executors of GitLab Runner.
 If you're using [GitLab Runner](../runners/index.md) with the Docker executor,
 you basically have everything set up already.
 
+NOTE:
+Variables set in the GitLab UI are not passed down to the service containers.
+[Learn more](../variables/index.md).
+
 First, in your `.gitlab-ci.yml` add:
 
 ```yaml
@@ -23,25 +27,19 @@ services:
   - postgres:12.2-alpine
 
 variables:
-  POSTGRES_DB: nice_marmot
-  POSTGRES_USER: runner
-  POSTGRES_PASSWORD: ""
+  POSTGRES_DB: $POSTGRES_DB
+  POSTGRES_USER: $POSTGRES_USER
+  POSTGRES_PASSWORD: $POSTGRES_PASSWORD
   POSTGRES_HOST_AUTH_METHOD: trust
 ```
 
-To set values for the `POSTGRES_DB`, `POSTGRES_USER`,
-`POSTGRES_PASSWORD` and `POSTGRES_HOST_AUTH_METHOD`,
-[assign them to a CI/CD variable in the user interface](../variables/index.md#custom-cicd-variables),
-then assign that variable to the corresponding variable in your
-`.gitlab-ci.yml` file.
-
 And then configure your application to use the database, for example:
 
 ```yaml
 Host: postgres
-User: runner
-Password: ''
-Database: nice_marmot
+User: $PG_USER
+Password: $PG_PASSWORD
+Database: $PG_DB
 ```
 
 If you're wondering why we used `postgres` for the `Host`, read more at

doc/ci/variables/index.md

@@ -20,6 +20,15 @@ You can use [predefined CI/CD variables](#predefined-cicd-variables) or define c
 - [Group CI/CD variables](#add-a-cicd-variable-to-a-group).
 - [Instance CI/CD variables](#add-a-cicd-variable-to-an-instance).
 
+NOTE:
+Variables set in the GitLab UI are **not** passed down to [service containers](../docker/using_docker_images.md).
+To set them, assign them to variables in the UI, then re-assign them in your `.gitlab-ci.yml`:
+
+```yaml
+variables:
+  SA_PASSWORD: $SA_PASSWORD
+```
+
 > For more information about advanced use of GitLab CI/CD:
 >
 > - <i class="fa fa-youtube-play youtube" aria-hidden="true"></i>&nbsp;Get to productivity faster with these [7 advanced GitLab CI workflow hacks](https://about.gitlab.com/webcast/7cicd-hacks/)