Add ServiceAccount doc (#2574)

* Add ServiceAccount doc

Signed-off-by: Yuri Sa <[email protected]>

* Add ServiceAccount doc

Signed-off-by: Yuri Sa <[email protected]>

---------

Signed-off-by: Yuri Sa <[email protected]>

Author: yuriolisa

README.md

@@ -189,6 +189,27 @@ EOF
 
 When using sidecar mode the OpenTelemetry collector container will have the environment variable `OTEL_RESOURCE_ATTRIBUTES`set with Kubernetes resource attributes, ready to be consumed by the [resourcedetection](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/resourcedetectionprocessor) processor.
 
+### Using imagePullSecrets
+
+The OpenTelemetry Collector defines a ServiceAccount field which could be set to run collector instances with a specific Service and their properties (e.g. imagePullSecrets). Therefore, if you have a constraint to run your collector with a private container registry, you should follow the procedure below:
+
+* Create Service Account.
+````bash
+kubectl create serviceaccount <service-account-name>
+````
+
+* Create an imagePullSecret.
+````bash
+kubectl create secret docker-registry <secret-name> --docker-server=<registry name> \
+        --docker-username=DUMMY_USERNAME --docker-password=DUMMY_DOCKER_PASSWORD \
+        --docker-email=DUMMY_DOCKER_EMAIL
+````
+
+* Add image pull secret to service account
+````bash
+kubectl patch serviceaccount <service-account-name> -p '{"imagePullSecrets": [{"name": "<secret-name>"}]}'
+````
+
 ### OpenTelemetry auto-instrumentation injection
 
 The operator can inject and configure OpenTelemetry auto-instrumentation libraries. Currently Apache HTTPD, DotNet, Go, Java, Nginx, NodeJS and Python are supported.