Prevent creation of volumes

ccp/modules/datashield-compose.yml

@@ -43,6 +43,8 @@ services:
     secrets:
       - opal-cert.pem
       - opal-key.pem
+    tmpfs:
+      - /srv
 
   opal-db:
     container_name: bridgehead-opal-db
@@ -57,6 +59,8 @@ services:
   opal-rserver:
     container_name: bridgehead-opal-rserver
     image: docker.verbis.dkfz.de/cache/datashield/rock-base:6.3  # https://datashield.discourse.group/t/ds-aggregate-method-error/416/4
+    tmpfs:
+      - /srv
 
   beam-connect:
     image: docker.verbis.dkfz.de/cache/samply/beam-connect:develop