Add entrypoint and command docs for service containers (#60567)

Co-authored-by: Salil <salilsub@users.noreply.github.com>
Co-authored-by: Sunbrye Ly <56200261+sunbrye@users.noreply.github.com>

Author: 3 people

content/actions/reference/workflows-and-actions/workflow-syntax.md

@@ -1182,6 +1182,45 @@ Additional Docker container resource options. For a list of options, see [`docke
 > [!WARNING]
 > The `--network` option is not supported.
 
+{% ifversion fpt or ghec %}
+
+## `jobs.<job_id>.services.<service_id>.command`
+
+Overrides the Docker image's default command (`CMD`). The value is passed as arguments after the image name in the `docker create` command. If you also specify `entrypoint`, `command` provides the arguments to that entrypoint.
+
+### Example of `jobs.<job_id>.services.<service_id>.command`
+
+```yaml
+services:
+  mysql:
+    image: mysql:8
+    command: --sql_mode=STRICT_TRANS_TABLES --max_allowed_packet=512M
+    env:
+      MYSQL_ROOT_PASSWORD: test
+    ports:
+      - 3306:3306
+```
+
+## `jobs.<job_id>.services.<service_id>.entrypoint`
+
+Overrides the Docker image's default `ENTRYPOINT`. The value is a single string defining the executable to run. Use this when you need to replace the image's entrypoint entirely. You can combine `entrypoint` with `command` to pass arguments to the custom entrypoint.
+
+### Example of `jobs.<job_id>.services.<service_id>.entrypoint`
+
+```yaml
+services:
+  etcd:
+    image: quay.io/coreos/etcd:v3.5.17
+    entrypoint: etcd
+    command: >-
+      --listen-client-urls http://0.0.0.0:2379
+      --advertise-client-urls http://0.0.0.0:2379
+    ports:
+      - 2379:2379
+```
+
+{% endif %}
+
 ## `jobs.<job_id>.uses`
 
 The location and version of a reusable workflow file to run as a job. Use one of the following syntaxes:

content/actions/tutorials/use-containerized-services/use-docker-service-containers.md

@@ -150,6 +150,43 @@ jobs:
 
 {% endraw %}
 
+{% ifversion fpt or ghec %}
+
+## Customizing service container entrypoints and commands
+
+By default, service containers run with the entrypoint and command defined in the Docker image. You can override these using the `entrypoint` and `command` keys. This is useful when you need to pass flags to a service (such as a database) or swap the image entrypoint entirely, without building a custom wrapper image.
+
+The `command` key overrides the image's default command (`CMD`). Most scenarios only need `command`—the image already has the right entrypoint, you just need to pass flags:
+
+```yaml copy
+services:
+  mysql:
+    image: mysql:8
+    command: --sql_mode=STRICT_TRANS_TABLES --max_allowed_packet=512M
+    env:
+      MYSQL_ROOT_PASSWORD: test
+    ports:
+      - 3306:3306
+```
+
+The `entrypoint` key overrides the image's `ENTRYPOINT`. You can combine it with `command` to pass arguments to the custom entrypoint:
+
+```yaml copy
+services:
+  etcd:
+    image: quay.io/coreos/etcd:v3.5.17
+    entrypoint: etcd
+    command: >-
+      --listen-client-urls http://0.0.0.0:2379
+      --advertise-client-urls http://0.0.0.0:2379
+    ports:
+      - 2379:2379
+```
+
+The naming and behavior match Docker Compose. For more information, see [`jobs.<job_id>.services.<service_id>.command`](/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idservicesservice_idcommand) and [`jobs.<job_id>.services.<service_id>.entrypoint`](/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idservicesservice_identrypoint).
+
+{% endif %}
+
 ## Further reading
 
 * [AUTOTITLE](/actions/using-containerized-services/creating-redis-service-containers)