Merge pull request #575 from eclipse-tractusx/docs/trg-403-align-on-userid

docs: adjust trg 4.03 on userid

Author: almadigabor

docs/release/trg-4/trg-4-03.md

@@ -4,6 +4,7 @@ title: TRG 4.03 - Non-root container
 
 | Status | Created      | Post-History                     |
 |--------|--------------|----------------------------------|
+| Active | 04-Jan-2024  | Adjust user ids                  |
 | Active | 29-Dec-2022  | Initial Release                  |
 | Draft  | 14-Sept-2022 | Draft                            |
 
@@ -19,14 +20,19 @@ For security reasons this is **must** be followed.
 
 The container's **Dockerfile** and the **Pod resource file (yaml)** has to be modified to be able to run as a non-root user.
 
-- Modify the image's Dockerfile with a `RUN` command that adds a non-root user and a `USER` command that specifies which user runs the container on startup. The example below can be modified for specific needs/requirements.
+- First it is recommended to check how the base image is built to see if it
+  might already have a non-root user defined and used. In this case it is enough
+  to specify that user in the Dockerfile with the `USER` instruction.
+- Otherwise modify the image's Dockerfile with a `RUN` command that adds a non-root user
+  and a `USER` command that specifies which user runs the container on startup.
+  The example below can be modified for specific needs/requirements.
 
 ```Dockerfile
 #Pull the base image as Ubuntu
 FROM ubuntu:latest
 
-#Add a user with userid 8877 and name nonroot
-RUN useradd −u 8877 nonroot
+#Add a user with userid 1000 and name nonroot
+RUN useradd −u 1000 nonroot
 
 #Run Container as nonroot
 USER nonroot
@@ -46,6 +52,5 @@ spec:
   - name: example-container
     image: gcr.io/google-samples/node-hello:1.0
     securityContext:
-      runAsUser: 1000 # SPECIFY USER ID HERE
       allowPrivilegeEscalation: false # SET THIS TO FALSE
 ```