diff --git a/containers/Dockerfile.base-centos7 b/containers/Dockerfile.base-centos7
index 257a42cc..d0997cdc 100644
--- a/containers/Dockerfile.base-centos7
+++ b/containers/Dockerfile.base-centos7
@@ -1,5 +1,10 @@
-FROM centos:7.8.2003
-# Set default easybuild version
+ARG IMG_REGISTRY=docker.io
+ARG IMG_ORG=library
+ARG IMG_NAME=centos
+ARG IMG_TAG=7.8.2003
+# allow CI/CD to change all of the above
+FROM ${IMG_REGISTRY}/${IMG_ORG}/${IMG_NAME}:${IMG_TAG}
+# set default easybuild version
 ARG EB_VER=4.2.1
 LABEL easybuild_version=${EB_VER}
 # install required packages (EPEL is required for Lmod)
@@ -39,4 +44,5 @@ USER root
 RUN pip3 uninstall -y easybuild
 # switch to 'easybuild' user
 USER easybuild
+# make sure we start in /home/easybuild rather than / when shell in started in container
 WORKDIR /home/easybuild
diff --git a/containers/Dockerfile.centos7-GCC-9.3.0 b/containers/Dockerfile.centos7-GCC-9.3.0
index bdc18968..aa67067a 100644
--- a/containers/Dockerfile.centos7-GCC-9.3.0
+++ b/containers/Dockerfile.centos7-GCC-9.3.0
@@ -1,4 +1,10 @@
-FROM easybuilders/base:centos7-eb4.2.1
+ARG IMG_REGISTRY=docker.io
+ARG IMG_ORG=easybuilders
+ARG IMG_NAME=base
+ARG IMG_TAG=centos7-eb4.2.1
+# allow CI/CD to change all of the above
+FROM ${IMG_REGISTRY}/${IMG_ORG}/${IMG_NAME}:${IMG_TAG}
+
 # CPU_ARCH is expected to be defined in the "docker build" command,
 # for example: docker build --build-arg CPU_ARCH=haswell
 ARG CPU_ARCH
diff --git a/containers/Dockerfile.centos7-foss2020a b/containers/Dockerfile.centos7-foss2020a
index 5c207601..331dfeb3 100644
--- a/containers/Dockerfile.centos7-foss2020a
+++ b/containers/Dockerfile.centos7-foss2020a
@@ -1,4 +1,10 @@
-FROM easybuilders/test:centos7-eb421-gcc930
+ARG IMG_REGISTRY=docker.io
+ARG IMG_ORG=easybuilders
+ARG IMG_NAME=test
+ARG IMG_TAG=centos7-eb421-gcc930
+# allow CI/CD to change all of the above
+FROM ${IMG_REGISTRY}/${IMG_ORG}/${IMG_NAME}:${IMG_TAG}
+
 # install software & accompanying modules
 RUN (eb foss-2020a.eb --robot || tail -100 `eb --last-log`) \
   # clean up everything in /scratch