updating README

README.md

@@ -190,6 +190,16 @@ docker network create -d overlay emg-extnet
 ```
 Add following .env files with credentials to the cloned copy of the repository /env folder: `vhr18_db.env`, `vhr18_obs.env`, `vhr18_django.env`.
 
+create docker secrets:
+
+Sensitive environment variables are not included in the .env files, and must be generated as docker secrets. To create docker secrets run :
+```bash
+# replace the "<variable>" with the value of the secret
+printf "<OS_PASSWORD_DOWNLOAD>" | docker secret create OS_PASSWORD_DOWNLOAD -
+printf "<DJANGO_PASSWORD>" | docker secret create DJANGO_PASSWORD -
+printf "<OS_PASSWORD>" | docker secret create OS_PASSWORD -
+```
+
 Deploy the stack:
 ```
 docker stack deploy -c docker-compose.vhr18.yml -c docker-compose.vhr18.dev.yml -c docker-compose.logging.yml -c docker-compose.logging.dev.yml vhr18-pvs  # start VHR_IMAGE_2018 stack in dev mode, for example to use local sources