Build containers from scratch and use ca-certificates and zoneinfo from latest alpine.

dockerfile/amd64/Dockerfile

@@ -1,4 +1,20 @@
-FROM centurylink/ca-certs
+#
+# Alpine image to get some needed data
+#
+FROM alpine:latest as alpine
+RUN apk add --no-cache \
+    ca-certificates \
+    tzdata
+
+#
+# Image
+#
+FROM scratch
 LABEL "com.centurylinklabs.watchtower"="true"
+
+# copy files from other containers
+COPY --from=alpine /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+COPY --from=alpine /usr/share/zoneinfo /usr/share/zoneinfo
+
 COPY watchtower /
 ENTRYPOINT ["/watchtower"]

dockerfile/armhf/Dockerfile

@@ -1,4 +1,20 @@
-FROM centurylink/ca-certs
+#
+# Alpine image to get some needed data
+#
+FROM alpine:latest as alpine
+RUN apk add --no-cache \
+    ca-certificates \
+    tzdata
+
+#
+# Image
+#
+FROM scratch
 LABEL "com.centurylinklabs.watchtower"="true"
+
+# copy files from other containers
+COPY --from=alpine /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+COPY --from=alpine /usr/share/zoneinfo /usr/share/zoneinfo
+
 COPY watchtower /
 ENTRYPOINT ["/watchtower"]