diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..48a6a20
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,4 @@
+.git
+scratchpad
+_build/cache
+_build/pkg
\ No newline at end of file
diff --git a/Makefile b/Makefile
index fccc302..265484c 100644
--- a/Makefile
+++ b/Makefile
@@ -17,15 +17,16 @@
 .DEFAULT_GOAL := help
 SHELL = /bin/bash
 
-REPO=dregsy
-DREGSY_VERSION=$$(git describe --always --tag --dirty)
+REPO = dregsy
+DREGSY_VERSION = $$(git describe --always --tag --dirty)
 
-BUILD_OUTPUT=_build
-BINARIES=$(BUILD_OUTPUT)/bin
-ISOLATED_PKG=$(BUILD_OUTPUT)/pkg
-ISOLATED_CACHE=$(BUILD_OUTPUT)/cache
+ROOT = $(shell pwd)
+BUILD_OUTPUT =_build
+BINARIES = $(BUILD_OUTPUT)/bin
+ISOLATED_PKG = $(BUILD_OUTPUT)/pkg
+ISOLATED_CACHE = $(BUILD_OUTPUT)/cache
 
-GO_IMAGE=golang:1.13.6-buster@sha256:f6cefbdd25f9a66ec7dcef1ee5deb417882b9db9629a724af8a332fe54e3f7b3
+GO_IMAGE = golang:1.13.6-buster@sha256:f6cefbdd25f9a66ec7dcef1ee5deb417882b9db9629a724af8a332fe54e3f7b3
 
 ## makerc
 # You need to set the following parameters in configuration file ${DIM}.makerc${NRM}, with every line
@@ -82,20 +83,20 @@ else
 endif
 
 ifeq ($(MAKECMDGOALS),release)
-	ISOLATED=y
+	ISOLATED = y
 endif
 
 ISOLATED ?=
 ifeq ($(ISOLATED),y)
-    CACHE_VOLS=-v $$(pwd)/$(ISOLATED_PKG):/go/pkg -v $$(pwd)/$(ISOLATED_CACHE):/.cache
+    CACHE_VOLS = -v $(ROOT)/$(ISOLATED_PKG):/go/pkg -v $(ROOT)/$(ISOLATED_CACHE):/.cache
 else
-    CACHE_VOLS=-v $(GOPATH)/pkg:/go/pkg -v /home/$(USER)/.cache:/.cache
+    CACHE_VOLS = -v $(GOPATH)/pkg:/go/pkg -v /home/$(USER)/.cache:/.cache
 endif
 
 ifeq ($(GCP_CREDENTIALS),)
-	GCP_CREDS=
+	GCP_CREDS =
 else
-	GCP_CREDS=-v $(GCP_CREDENTIALS):/var/run/secrets/gcp-creds.json -e GOOGLE_APPLICATION_CREDENTIALS=/var/run/secrets/gcp-creds.json
+	GCP_CREDS = -v $(GCP_CREDENTIALS):/var/run/secrets/gcp-creds.json -e GOOGLE_APPLICATION_CREDENTIALS=/var/run/secrets/gcp-creds.json
 endif
 
 export
@@ -111,7 +112,7 @@ help:
 
 
 .PHONY: release
-release: clean rmi dregsy imgdregsy imgtests registryrestart tests registrydown
+release: clean rmi dregsy imgdregsy imgtests tests registrydown
 #	clean, do an isolated build, create container images, and test
 #
 
@@ -131,72 +132,78 @@ dregsy: prep
 
 .PHONY: imgdregsy
 imgdregsy:
-#	build the ${ITL}dregsy${NRM} container image; assumes binary was built
+#	build the ${ITL}dregsy${NRM} container images (Alpine and Ubuntu based);
+#	assumes binary was built
 #
-	docker build -t xelalex/$(REPO) -f ./hack/dregsy.Dockerfile \
-		--build-arg binaries=$(BINARIES) .
+	echo -e "\nBuilding Alpine-based image...\n"
+	docker build -t xelalex/$(REPO):latest-alpine \
+		-f ./hack/dregsy.alpine.Dockerfile --build-arg binaries=$(BINARIES) .
+	# for historical reasons, the `xelalex/dregsy` image is the Alpine image
+	docker tag xelalex/$(REPO):latest-alpine xelalex/$(REPO):latest
+	echo -e "\n\nBuilding Ubuntu-based image...\n"
+	docker build -t xelalex/$(REPO):latest-ubuntu \
+		-f ./hack/dregsy.ubuntu.Dockerfile --build-arg binaries=$(BINARIES) .
+	echo -e "\nDone\n"
 
 
 .PHONY: imgtests
 imgtests:
-#	build the container image for running tests; assumes ${ITL}dregsy${NRM} image was built
+#	build the container images for running tests (Alpine and Ubuntu based);
+#	assumes ${ITL}dregsy-...${NRM} images were built
 #
-	docker build -t xelalex/$(REPO)-tests -f ./hack/tests.Dockerfile .
+	echo -e "\nBuilding Alpine-based test image...\n"
+	docker build -t xelalex/$(REPO)-tests-alpine \
+		-f ./hack/tests.alpine.Dockerfile .
+	echo -e "\n\nBuilding Ubuntu-based test image...\n"
+	docker build -t xelalex/$(REPO)-tests-ubuntu \
+		-f ./hack/tests.ubuntu.Dockerfile .
+	echo -e "\nDone\n"
 
 
 .PHONY: rmi
 rmi:
 #	remove the ${ITL}dregsy${NRM} and testing container images
 #
-	docker rmi -f xelalex/$(REPO)
-	docker rmi -f xelalex/$(REPO)-tests
+	docker rmi -f xelalex/$(REPO):latest
+	docker rmi -f xelalex/$(REPO):latest-alpine
+	docker rmi -f xelalex/$(REPO):latest-ubuntu
+	docker rmi -f xelalex/$(REPO)-tests-alpine
+	docker rmi -f xelalex/$(REPO)-tests-ubuntu
 
 
 .PHONY: tests
 tests: prep
-#	run tests; assumes tests image was built and local ${ITL}Docker${NRM} registry running
-#	on localhost:5000 (start with ${DIM}make registryup${NRM});
+#	run tests; assumes test images were built; local ${ITL}Docker${NRM} registry gets
+#	(re-)started on localhost:5000
 #
 ifeq (,$(wildcard .makerc))
 	$(warning ***** Missing .makerc! Some tests may be skipped or fail!)
 endif
-	@echo -e "\ntests:"
-	docker run --privileged --network host --rm  \
-		-v $(shell pwd):/go/src/$(REPO) -w /go/src/$(REPO) \
-		-v $(shell pwd)/$(BINARIES):/go/bin \
-		-v /var/run/docker.sock:/var/run/docker.sock \
-		$(CACHE_VOLS) \
-		$(GCP_CREDS) \
-		-e CGO_ENABLED=0 -e GOOS=linux -e GOARCH=amd64 \
-		-e LOG_LEVEL=debug -e LOG_FORMAT=text -e LOG_FORCE_COLORS=true \
-		--env-file <(sed -E 's/\ +=\ +/=/g' .makerc) \
-		xelalex/$(REPO)-tests sh -c "\
-			go test $(TEST_OPTS) \
-				-coverpkg=./... -coverprofile=$(BUILD_OUTPUT)/coverage.out \
-				-covermode=count ./... && \
-			go tool cover -html=$(BUILD_OUTPUT)/coverage.out \
-				-o $(BUILD_OUTPUT)/coverage.html"
-	@echo -e "\ncoverage report is in $(BUILD_OUTPUT)/coverage.html\n"
+	$(call utils, registry_restart)
+	$(call utils, run_tests alpine)
+	$(call utils, registry_restart)
+	$(call utils, run_tests ubuntu)
 
 
 .PHONY: registryup
 registryup:
 #	start local ${ITL}Docker${NRM} registry for running tests
 #
-	docker run -d --rm -p 5000:5000 --name dregsy-test-registry registry:2
+	$(call utils, registry_up)
 
 
 .PHONY: registrydown
 registrydown:
 #	stop local ${ITL}Docker${NRM} registry
 #
-	docker stop dregsy-test-registry || true
+	$(call utils, registry_down) || true
 
 
 .PHONY: registryrestart
-registryrestart: registrydown registryup
+registryrestart:
 #	restart local ${ITL}Docker${NRM} registry
 #
+	$(call utils, registry_restart)
 
 
 .PHONY: clean
diff --git a/hack/devenvutil b/hack/devenvutil
index 21c6e28..4c988db 100755
--- a/hack/devenvutil
+++ b/hack/devenvutil
@@ -38,6 +38,8 @@ function synopsis {
 
     files=()
 
+    command -v gawk > /dev/null || echo "Note: proper help display requires gawk!"
+
     for file in ${MAKEFILE_LIST}; do
         if [[ "$(basename "${file}")" == "Makefile" ]]; then
             files+=( "../${file}" )
@@ -100,6 +102,53 @@ function apply_shell_expansion {
     eval "${command}"
 }
 
+#
+#
+#
+function registry_up {
+    docker run -d --rm -p 5000:5000 --name dregsy-test-registry registry:2
+}
+
+#
+#
+#
+function registry_down {
+    docker stop dregsy-test-registry
+}
+
+#
+#
+#
+function registry_restart {
+    registry_down
+    registry_up
+}
+
+#
+# $1    test image variant (`alpine` or `ubuntu`)
+#
+function run_tests {
+
+    echo -e "\ntesting using $1-based image:"
+
+    docker run --privileged --network host --rm  \
+        -v "${ROOT}:/go/src/${REPO}" -w "/go/src/${REPO}" \
+        -v "${ROOT}/${BINARIES}:/go/bin" \
+        -v /var/run/docker.sock:/var/run/docker.sock \
+        ${CACHE_VOLS} ${GCP_CREDS} \
+        -e CGO_ENABLED=0 -e GOOS=linux -e GOARCH=amd64 \
+        -e LOG_LEVEL=debug -e LOG_FORMAT=text -e LOG_FORCE_COLORS=true \
+        --env-file <(sed -E 's/\ +=\ +/=/g' "${ROOT}/.makerc") \
+        "xelalex/${REPO}-tests-$1" sh -c "\
+            go test ${TEST_OPTS} \
+                -coverpkg=./... -coverprofile=${BUILD_OUTPUT}/coverage.out \
+                -covermode=count ./... && \
+            go tool cover -html=${BUILD_OUTPUT}/coverage.out \
+                -o ${BUILD_OUTPUT}/coverage-$1.html"
+
+    echo -e "\ncoverage report is in ${BUILD_OUTPUT}/coverage-$1.html\n"
+}
+
 #
 #
 #
diff --git a/hack/dregsy.Dockerfile b/hack/dregsy.alpine.Dockerfile
similarity index 100%
rename from hack/dregsy.Dockerfile
rename to hack/dregsy.alpine.Dockerfile
diff --git a/hack/dregsy.ubuntu.Dockerfile b/hack/dregsy.ubuntu.Dockerfile
new file mode 100644
index 0000000..146c73b
--- /dev/null
+++ b/hack/dregsy.ubuntu.Dockerfile
@@ -0,0 +1,50 @@
+#
+# Copyright 2021 Alexander Vollschwitz
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+FROM docker.io/ubuntu:20.04@sha256:c65d2b75a62135c95e2c595822af9b6f6cf0f32c11bcd4a38368d7b7c36b66f5
+
+LABEL maintainer "vollschwitz@gmx.net"
+
+ARG binaries
+
+ENV DEBIAN_FRONTEND=noninteractive
+ENV APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=yes
+
+RUN apt-get update && \
+    apt-get upgrade -y --fix-missing && \
+    apt-get install -y --no-install-recommends --fix-missing \
+        ca-certificates \
+        apt-utils \
+        gpg \
+        curl && \
+    echo 'deb http://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_20.04/ /' \
+        > /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list && \
+    curl -fsSL https://download.opensuse.org/repositories/devel:kubic:libcontainers:stable/xUbuntu_20.04/Release.key \
+        | gpg --dearmor > /etc/apt/trusted.gpg.d/devel_kubic_libcontainers_stable.gpg && \
+    apt-get update && \
+    apt-get install -y --no-install-recommends --fix-missing \
+        skopeo=100:1.2.2-2 && \
+    apt-get clean -y && \
+    rm -rf \
+        /var/cache/debconf/* \
+        /var/lib/apt/lists/* \
+        /var/log/* \
+        /tmp/* \
+        /var/tmp/*
+
+COPY ${binaries}/dregsy /usr/local/bin
+
+CMD ["dregsy", "-config=config.yaml"]
diff --git a/hack/tests.Dockerfile b/hack/tests.alpine.Dockerfile
similarity index 81%
rename from hack/tests.Dockerfile
rename to hack/tests.alpine.Dockerfile
index f11cf42..1d64970 100644
--- a/hack/tests.Dockerfile
+++ b/hack/tests.alpine.Dockerfile
@@ -14,7 +14,7 @@
 # limitations under the License.
 #
 
-FROM xelalex/dregsy:latest
+FROM xelalex/dregsy:latest-alpine
 
 # install & configure Go
 RUN apk add --no-cache go
@@ -28,10 +28,10 @@ RUN mkdir -p ${GOPATH}/src ${GOPATH}/bin ${GOPATH}/pkg ${GOCACHE}
 ARG USER=go
 ENV HOME /home/${USER}
 RUN apk add --update sudo
-RUN adduser -D ${USER} \
-	&& adduser ${USER} ping \
-    && echo "${USER} ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/${USER} \
-    && chmod 0440 /etc/sudoers.d/${USER}
+RUN adduser -D ${USER} && \
+    adduser ${USER} ping && \
+    echo "${USER} ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/${USER} && \
+    chmod 0440 /etc/sudoers.d/${USER}
 USER ${USER}
 
 WORKDIR ${GOPATH}
diff --git a/hack/tests.ubuntu.Dockerfile b/hack/tests.ubuntu.Dockerfile
new file mode 100644
index 0000000..2c18e08
--- /dev/null
+++ b/hack/tests.ubuntu.Dockerfile
@@ -0,0 +1,47 @@
+#
+# Copyright 2021 Alexander Vollschwitz
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+FROM xelalex/dregsy:latest-ubuntu
+
+# install & configure Go
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends --fix-missing \
+        golang && \
+    apt-get clean -y && \
+    rm -rf \
+        /var/cache/debconf/* \
+        /var/lib/apt/lists/* \
+        /var/log/* \
+        /tmp/* \
+        /var/tmp/*
+
+ENV GOROOT /usr/lib/go
+ENV GOPATH /go
+ENV GOCACHE /.cache
+ENV PATH /go/bin:${PATH}
+RUN mkdir -p ${GOPATH}/src ${GOPATH}/bin ${GOPATH}/pkg ${GOCACHE}
+
+# non-root user
+ARG USER=go
+RUN groupadd -g ${GROUP_ID:-1000} ${USER} && \
+    useradd -l -u ${USER_ID:-1000} -g ${USER} ${USER} && \
+    install -d -m 0755 -o ${USER} -g ${USER} /home/${USER}
+ENV HOME /home/${USER}
+USER ${USER}
+
+WORKDIR ${GOPATH}
+
+CMD ["go", "version"]