Reduce footprint of UBI images (#717)

* Reduce footprint of UBI images by only keeping relevant packages and rpm DB

Signed-off-by: jack-baines <jack.baines@uk.ibm.com>

* Fix bash syntax error

Signed-off-by: jack-baines <jack.baines@uk.ibm.com>

* Add missing ARG

Signed-off-by: jack-baines <jack.baines@uk.ibm.com>

* TARGETARCH set by buildx and avoids splitting another VAR

Signed-off-by: jack-baines <jack.baines@uk.ibm.com>

* Update Dockerfile.ubi

Change top level build label to avoid confusion

---------

Signed-off-by: jack-baines <jack.baines@uk.ibm.com>

Dockerfile.ubi

@@ -3,16 +3,37 @@ ARG BASE_IMAGE
 
 FROM --platform=${BUILDPLATFORM} ${BUILDER_IMAGE} as SRC
 
-FROM ${BASE_IMAGE:-registry.access.redhat.com/ubi8/ubi-minimal:latest}
+FROM ${BASE_IMAGE:-registry.access.redhat.com/ubi8/ubi:latest} as ubi
+ARG TARGETARCH
 
+
+RUN dnf update -y && dnf install -y binutils
+# prep target rootfs for scratch container
 WORKDIR /
-COPY --from=SRC /manager .
+RUN mkdir /image && \
+    ln -s usr/bin /image/bin && \
+	ln -s usr/sbin /image/sbin && \
+	ln -s usr/lib64 /image/lib64 && \
+	ln -s usr/lib /image/lib && \
+	mkdir -p /image/{usr/bin,usr/lib64,usr/lib,root,home,proc,etc,sys,var,dev}
 
-# Update image
-RUN microdnf update
+COPY ubi-build-files-${TARGETARCH}.txt /tmp
+# Copy all the required files from the base UBI image into the image directory
+# As the go binary is not statically compiled this includes everything needed for CGO to work, cacerts, tzdata and RH release files
+RUN tar cf /tmp/files.tar -T /tmp/ubi-build-files-${TARGETARCH}.txt && tar xf /tmp/files.tar -C /image/ \
+  && strip --strip-unneeded /image/usr/lib64/*[0-9].so
 
-USER 65532:65532
+# Generate a rpm database which contains all the packages that you said were needed in ubi-build-files-*.txt
+RUN rpm --root /image --initdb \
+  && PACKAGES=$(rpm -qf $(cat /tmp/ubi-build-files-${TARGETARCH}.txt) | grep -v "is not owned by any package" | sort -u) \
+  && echo dnf install -y 'dnf-command(download)' \
+  && dnf download --destdir / ${PACKAGES} \
+  && rpm --root /image -ivh --justdb --nodeps `for i in ${PACKAGES}; do echo $i.rpm; done`
 
+FROM scratch
+COPY --from=ubi /image/ /
+COPY --from=SRC /manager .
+USER 65532:65532
 # Port for metrics and probes
 EXPOSE 9090
 

ubi-build-files-amd64.txt

@@ -0,0 +1,15 @@
+etc/pki
+root/buildinfo
+etc/ssl/certs
+etc/redhat-release
+usr/share/zoneinfo
+usr/lib64/ld-2.28.so
+usr/lib64/ld-linux-x86-64.so.2
+usr/lib64/libc-2.28.so
+usr/lib64/libc.so.6
+usr/lib64/libdl-2.28.so
+usr/lib64/libdl.so.2
+usr/lib64/libpthread-2.28.so
+usr/lib64/libpthread.so.0
+usr/lib64/libm-2.28.so
+usr/lib64/libm.so.6

ubi-build-files-arm64.txt

@@ -0,0 +1,15 @@
+etc/pki
+root/buildinfo
+etc/ssl/certs
+etc/redhat-release
+usr/share/zoneinfo
+usr/lib64/ld-2.28.so
+usr/lib64/ld-linux-aarch64.so.1
+usr/lib64/libc-2.28.so
+usr/lib64/libc.so.6
+usr/lib64/libdl-2.28.so
+usr/lib64/libdl.so.2
+usr/lib64/libpthread-2.28.so
+usr/lib64/libpthread.so.0
+usr/lib64/libm-2.28.so
+usr/lib64/libm.so.6