Add distroless Docker image variant

Introduces distroless image using UID/GID 65532 instead of nobody,
and removes VOLUME declaration. Busybox image remains default with
unchanged tags for backwards compatibility.

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>

Dockerfile

@@ -9,7 +9,8 @@ LABEL org.opencontainers.image.authors="The Prometheus Authors" \
       org.opencontainers.image.source="https://github.com/prometheus/prometheus" \
       org.opencontainers.image.url="https://github.com/prometheus/prometheus" \
       org.opencontainers.image.documentation="https://prometheus.io/docs" \
-      org.opencontainers.image.licenses="Apache License 2.0"
+      org.opencontainers.image.licenses="Apache License 2.0" \
+      io.prometheus.image.variant="busybox"
 
 ARG ARCH="amd64"
 ARG OS="linux"

Dockerfile.distroless

@@ -0,0 +1,26 @@
+FROM gcr.io/distroless/static-debian13:nonroot@sha256:f9f84bd968430d7d35e8e6d55c40efb0b980829ec42920a49e60e65eac0d83fc
+# Base image sets USER to 65532:65532 (nonroot user).
+
+ARG ARCH="amd64"
+ARG OS="linux"
+
+LABEL org.opencontainers.image.authors="The Prometheus Authors"
+LABEL org.opencontainers.image.vendor="Prometheus"
+LABEL org.opencontainers.image.title="Prometheus"
+LABEL org.opencontainers.image.description="The Prometheus monitoring system and time series database"
+LABEL org.opencontainers.image.source="https://github.com/prometheus/prometheus"
+LABEL org.opencontainers.image.url="https://github.com/prometheus/prometheus"
+LABEL org.opencontainers.image.documentation="https://prometheus.io/docs"
+LABEL org.opencontainers.image.licenses="Apache License 2.0"
+LABEL io.prometheus.image.variant="distroless"
+
+COPY documentation/examples/prometheus.yml  /etc/prometheus/prometheus.yml
+COPY LICENSE NOTICE npm_licenses.tar.bz2 /
+COPY .build/${OS}-${ARCH}/prometheus        /bin/prometheus
+COPY .build/${OS}-${ARCH}/promtool          /bin/promtool
+
+WORKDIR /prometheus
+EXPOSE     9090
+ENTRYPOINT [ "/bin/prometheus" ]
+CMD        [ "--config.file=/etc/prometheus/prometheus.yml", \
+             "--storage.tsdb.path=/prometheus" ]

Makefile.common

@@ -82,11 +82,32 @@ endif
 PREFIX                  ?= $(shell pwd)
 BIN_DIR                 ?= $(shell pwd)
 DOCKER_IMAGE_TAG        ?= $(subst /,-,$(shell git rev-parse --abbrev-ref HEAD))
-DOCKERFILE_PATH         ?= ./Dockerfile
 DOCKERBUILD_CONTEXT     ?= ./
 DOCKER_REPO             ?= prom
 
+# Check if deprecated DOCKERFILE_PATH is set
+ifdef DOCKERFILE_PATH
+$(error DOCKERFILE_PATH is deprecated. Use DOCKERFILE_VARIANTS ?= $(DOCKERFILE_PATH) in the Makefile)
+endif
+
 DOCKER_ARCHS            ?= amd64
+DOCKERFILE_VARIANTS     ?= Dockerfile $(wildcard Dockerfile.*)
+
+# Function to extract variant from Dockerfile label.
+# Returns the variant name from io.prometheus.image.variant label, or "default" if not found.
+define dockerfile_variant
+$(strip $(or $(shell sed -n 's/.*io\.prometheus\.image\.variant="\([^"]*\)".*/\1/p' $(1)),default))
+endef
+
+# Check for duplicate variant names (including default for Dockerfiles without labels).
+DOCKERFILE_VARIANT_NAMES := $(foreach df,$(DOCKERFILE_VARIANTS),$(call dockerfile_variant,$(df)))
+DOCKERFILE_VARIANT_NAMES_SORTED := $(sort $(DOCKERFILE_VARIANT_NAMES))
+ifneq ($(words $(DOCKERFILE_VARIANT_NAMES)),$(words $(DOCKERFILE_VARIANT_NAMES_SORTED)))
+$(error Duplicate variant names found. Each Dockerfile must have a unique io.prometheus.image.variant label, and only one can be without a label (default))
+endif
+
+# Build variant:dockerfile pairs for shell iteration.
+DOCKERFILE_VARIANTS_WITH_NAMES := $(foreach df,$(DOCKERFILE_VARIANTS),$(call dockerfile_variant,$(df)):$(df))
 
 BUILD_DOCKER_ARCHS = $(addprefix common-docker-,$(DOCKER_ARCHS))
 PUBLISH_DOCKER_ARCHS = $(addprefix common-docker-publish-,$(DOCKER_ARCHS))
@@ -226,28 +247,82 @@ common-docker-repo-name:
 .PHONY: common-docker $(BUILD_DOCKER_ARCHS)
 common-docker: $(BUILD_DOCKER_ARCHS)
 $(BUILD_DOCKER_ARCHS): common-docker-%:
-	docker build -t "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" \
+	@for variant in $(DOCKERFILE_VARIANTS_WITH_NAMES); do \
-		-f $(DOCKERFILE_PATH) \
+		dockerfile=$${variant#*:}; \
-		--build-arg ARCH="$*" \
+		variant_name=$${variant%%:*}; \
-		--build-arg OS="linux" \
+		if [ "$$dockerfile" = "Dockerfile" ]; then \
-		$(DOCKERBUILD_CONTEXT)
+			echo "Building default variant ($$variant_name) for linux-$* using $$dockerfile"; \
+			docker build -t "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" \
+				-f $$dockerfile \
+				--build-arg ARCH="$*" \
+				--build-arg OS="linux" \
+				$(DOCKERBUILD_CONTEXT); \
+			if [ "$$variant_name" != "default" ]; then \
+				echo "Tagging default variant with $$variant_name suffix"; \
+				docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" \
+					"$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name"; \
+			fi; \
+		else \
+			echo "Building $$variant_name variant for linux-$* using $$dockerfile"; \
+			docker build -t "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name" \
+				-f $$dockerfile \
+				--build-arg ARCH="$*" \
+				--build-arg OS="linux" \
+				$(DOCKERBUILD_CONTEXT); \
+		fi; \
+	done
 
 .PHONY: common-docker-publish $(PUBLISH_DOCKER_ARCHS)
 common-docker-publish: $(PUBLISH_DOCKER_ARCHS)
 $(PUBLISH_DOCKER_ARCHS): common-docker-publish-%:
-	docker push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)"
+	@for variant in $(DOCKERFILE_VARIANTS_WITH_NAMES); do \
+		dockerfile=$${variant#*:}; \
+		variant_name=$${variant%%:*}; \
+		if [ "$$dockerfile" != "Dockerfile" ] || [ "$$variant_name" != "default" ]; then \
+			echo "Pushing $$variant_name variant for linux-$*"; \
+			docker push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name"; \
+		fi; \
+		if [ "$$dockerfile" = "Dockerfile" ]; then \
+			echo "Pushing default variant ($$variant_name) for linux-$*"; \
+			docker push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)"; \
+		fi; \
+	done
 
 DOCKER_MAJOR_VERSION_TAG = $(firstword $(subst ., ,$(shell cat VERSION)))
 .PHONY: common-docker-tag-latest $(TAG_DOCKER_ARCHS)
 common-docker-tag-latest: $(TAG_DOCKER_ARCHS)
 $(TAG_DOCKER_ARCHS): common-docker-tag-latest-%:
-	docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:latest"
+	@for variant in $(DOCKERFILE_VARIANTS_WITH_NAMES); do \
-	docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:v$(DOCKER_MAJOR_VERSION_TAG)"
+		dockerfile=$${variant#*:}; \
+		variant_name=$${variant%%:*}; \
+		if [ "$$dockerfile" != "Dockerfile" ] || [ "$$variant_name" != "default" ]; then \
+			echo "Tagging $$variant_name variant for linux-$* as latest"; \
+			docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:latest-$$variant_name"; \
+			docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:v$(DOCKER_MAJOR_VERSION_TAG)-$$variant_name"; \
+		fi; \
+		if [ "$$dockerfile" = "Dockerfile" ]; then \
+			echo "Tagging default variant ($$variant_name) for linux-$* as latest"; \
+			docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:latest"; \
+			docker tag "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:$(SANITIZED_DOCKER_IMAGE_TAG)" "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$*:v$(DOCKER_MAJOR_VERSION_TAG)"; \
+		fi; \
+	done
 
 .PHONY: common-docker-manifest
 common-docker-manifest:
-	DOCKER_CLI_EXPERIMENTAL=enabled docker manifest create -a "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)" $(foreach ARCH,$(DOCKER_ARCHS),$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$(ARCH):$(SANITIZED_DOCKER_IMAGE_TAG))
+	@for variant in $(DOCKERFILE_VARIANTS_WITH_NAMES); do \
-	DOCKER_CLI_EXPERIMENTAL=enabled docker manifest push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)"
+		dockerfile=$${variant#*:}; \
+		variant_name=$${variant%%:*}; \
+		if [ "$$dockerfile" != "Dockerfile" ] || [ "$$variant_name" != "default" ]; then \
+			echo "Creating manifest for $$variant_name variant"; \
+			DOCKER_CLI_EXPERIMENTAL=enabled docker manifest create -a "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name" $(foreach ARCH,$(DOCKER_ARCHS),$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$(ARCH):$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name); \
+			DOCKER_CLI_EXPERIMENTAL=enabled docker manifest push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)-$$variant_name"; \
+		fi; \
+		if [ "$$dockerfile" = "Dockerfile" ]; then \
+			echo "Creating default variant ($$variant_name) manifest"; \
+			DOCKER_CLI_EXPERIMENTAL=enabled docker manifest create -a "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)" $(foreach ARCH,$(DOCKER_ARCHS),$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME)-linux-$(ARCH):$(SANITIZED_DOCKER_IMAGE_TAG)); \
+			DOCKER_CLI_EXPERIMENTAL=enabled docker manifest push "$(DOCKER_REPO)/$(DOCKER_IMAGE_NAME):$(SANITIZED_DOCKER_IMAGE_TAG)"; \
+		fi; \
+	done
 
 .PHONY: promu
 promu: $(PROMU)