add gosu

Dockerfile

@@ -29,4 +29,25 @@ RUN set -eux && \
 	locale -a | grep 'en_US.utf8'
 ENV LANG=en_US.utf8
 
+ENV GOSU_VERSION 1.19
+RUN set -eux; \
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends ca-certificates gnupg wget; \
+	rm -rf /var/lib/apt/lists/*; \
+	dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')"; \
+	wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch"; \
+	wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch.asc"; \
+	export GNUPGHOME="$(mktemp -d)"; \
+	gpg --batch --keyserver hkps://keys.openpgp.org --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4; \
+	gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu; \
+	gpgconf --kill all; \
+	rm -rf "$GNUPGHOME" /usr/local/bin/gosu.asc; \
+	apt-mark auto '.*' > /dev/null; \
+	[ -z "$savedAptMark" ] || apt-mark manual $savedAptMark > /dev/null; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	chmod +x /usr/local/bin/gosu; \
+	gosu --version; \
+	gosu nobody true
+
 ENTRYPOINT ["bash"]