[Dockerfiles] Used best practices for apt-get

See https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/#apt-get

- Replaced `-y install` with `install -y` (unification)

- Put every package on its own line

- Moved `rm -rf /var/lib/apt/lists/*` in the same `RUN` statement as `apt-get`

- Removed unnecessary `apt-get clean`
  See https://github.com/moby/moby/blob/03e2923e42446dbb830c654d0eec323a0b4ef02a/contrib/mkimage/debootstrap#L82-L105

data/Dockerfiles/clamav/Dockerfile

@@ -8,14 +8,12 @@ ENV DEBIAN_VERSION stretch
 RUN echo "deb http://http.debian.net/debian/ $DEBIAN_VERSION main contrib non-free" > /etc/apt/sources.list && \
 	echo "deb http://http.debian.net/debian/ $DEBIAN_VERSION-updates main contrib non-free" >> /etc/apt/sources.list && \
 	echo "deb http://security.debian.org/ $DEBIAN_VERSION/updates main contrib non-free" >> /etc/apt/sources.list && \
-	apt-get update && \
-	DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y -qq \
+	apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends \
 		clamav-daemon \
 		clamav-freshclam \
 		libclamunrar7 \
-		curl && \
-	apt-get clean && \
-	rm -rf /var/lib/apt/lists/*
+		curl \
+	&& rm -rf /var/lib/apt/lists/*
 
 # initial update of av databases
 COPY dl_files.sh /dl_files.sh

data/Dockerfiles/dovecot/Dockerfile

@@ -7,8 +7,8 @@ ENV LC_ALL C
 ENV DOVECOT_VERSION 2.2.29.1
 ENV PIGEONHOLE_VERSION 0.4.18
 
-RUN apt-get update \
-	&& apt-get -y install libpam-dev \
+RUN apt-get update && apt-get -y install \
+	libpam-dev \
 	default-libmysqlclient-dev \
 	lzma-dev \
 	liblz-dev \
@@ -48,7 +48,8 @@ RUN apt-get update \
 	libdbd-mysql-perl \
 	libipc-run-perl \
 	make \
-	cpanminus
+	cpanminus \
+	&& rm -rf /var/lib/apt/lists/*
 
 
 RUN wget https://www.dovecot.org/releases/2.2/dovecot-$DOVECOT_VERSION.tar.gz -O - | tar xvz  \
@@ -100,8 +101,7 @@ EXPOSE 24 10001
 ENTRYPOINT ["/docker-entrypoint.sh"]
 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf
 
-RUN apt-get clean \
-	&& rm -rf /var/lib/apt/lists/* \
+RUN rm -rf \
 	/tmp/* \
 	/var/tmp/* \
 	/dovecot-2.2-pigeonhole-$PIGEONHOLE_VERSION \

data/Dockerfiles/php-fpm/Dockerfile

@@ -3,14 +3,15 @@ LABEL maintainer "Andre Peters <andre.peters@servercow.de>"
 
 ENV DEBIAN_FRONTEND noninteractive
 
-RUN apt-get update \
-	&& apt-get install -y zlib1g-dev \
+RUN apt-get update && apt-get install -y \
+	zlib1g-dev \
 	libicu-dev \
 	g++ \
 	libidn11-dev \
 	libxml2-dev \
 	redis-tools \
-	mysql-client
+	mysql-client \
+	&& rm -rf /var/lib/apt/lists/*
 
 RUN docker-php-ext-configure intl
 RUN docker-php-ext-install intl pdo pdo_mysql xmlrpc

data/Dockerfiles/postfix/Dockerfile

@@ -9,8 +9,8 @@ RUN dpkg-divert --local --rename --add /sbin/initctl \
 	&& dpkg-divert --local --rename --add /usr/bin/ischroot \
 	&& ln -sf /bin/true /usr/bin/ischroot
 
-RUN apt-get update
-RUN apt-get install -y --no-install-recommends supervisor \
+RUN apt-get update && apt-get install -y --no-install-recommends \
+	supervisor \
 	postfix \
 	sasl2-bin \
 	libsasl2-modules \
@@ -25,7 +25,8 @@ RUN apt-get install -y --no-install-recommends supervisor \
 	python-gpgme \
 	sudo \
 	curl \
-	dirmngr
+	dirmngr \
+	&& rm -rf /var/lib/apt/lists/*
 
 RUN addgroup --system --gid 600 zeyple
 RUN adduser --system --home /var/lib/zeyple --no-create-home --uid 600 --gid 600 --disabled-login zeyple
@@ -44,4 +45,4 @@ EXPOSE 588
 
 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf
 
-RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+RUN rm -rf /tmp/* /var/tmp/*

data/Dockerfiles/rmilter/Dockerfile

@@ -6,8 +6,13 @@ ENV LC_ALL C
 
 RUN apt-key adv --fetch-keys http://rspamd.com/apt-stable/gpg.key \
 	&& echo "deb http://rspamd.com/apt-stable/ jessie main" > /etc/apt/sources.list.d/rspamd.list \
-	&& apt-get update \
-	&& apt-get --no-install-recommends -y --force-yes install rmilter cron syslog-ng syslog-ng-core supervisor
+	&& apt-get update && apt-get install -y --force-yes --no-install-recommends \
+		rmilter \
+		cron \
+		syslog-ng \
+		syslog-ng-core \
+		supervisor \
+	&& rm -rf /var/lib/apt/lists/*
 
 COPY supervisord.conf /etc/supervisor/supervisord.conf
 
@@ -18,4 +23,4 @@ RUN touch /var/log/mail.log && chmod 640 /var/log/mail.log && chown root:adm /va
 
 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf
 
-RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+RUN rm -rf /tmp/* /var/tmp/*

data/Dockerfiles/rspamd/Dockerfile

@@ -6,8 +6,11 @@ ENV LC_ALL C
 
 RUN apt-key adv --fetch-keys http://rspamd.com/apt-stable/gpg.key \
 	&& echo "deb http://rspamd.com/apt-stable/ jessie main" > /etc/apt/sources.list.d/rspamd.list \
-	&& apt-get update \
-	&& apt-get -y install rspamd ca-certificates python-pip
+	&& apt-get update && apt-get install -y \
+		rspamd \
+		ca-certificates \
+		python-pip \
+	&& rm -rf /var/lib/apt/lists/*
 
 RUN echo '.include $LOCAL_CONFDIR/local.d/rspamd.conf.local' > /etc/rspamd/rspamd.conf.local
 
@@ -18,7 +21,7 @@ RUN pip install -U oletools
 
 CMD /usr/bin/rspamd -f -u _rspamd -g _rspamd
 
-RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+RUN rm -rf /tmp/* /var/tmp/*
 
 USER _rspamd
 

data/Dockerfiles/sogo/Dockerfile

@@ -5,8 +5,9 @@ ENV DEBIAN_FRONTEND noninteractive
 ENV LC_ALL C
 ENV GOSU_VERSION 1.9
 
-RUN apt-get update \
-	&& apt-get install -y --no-install-recommends apt-transport-https gnupg \
+RUN apt-get update && apt-get install -y --no-install-recommends \
+		apt-transport-https \
+		gnupg \
 		ca-certificates \
 		wget \
 		syslog-ng \
@@ -14,6 +15,7 @@ RUN apt-get update \
 		supervisor \
 		mysql-client \
 		cron \
+	&& 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" \
@@ -29,8 +31,10 @@ RUN touch /usr/share/doc/sogo/empty.sh
 
 RUN apt-key adv --keyserver keys.gnupg.net --recv-key 0x810273C4 \
 	&& echo "deb http://packages.inverse.ca/SOGo/nightly/3/debian/ jessie jessie" > /etc/apt/sources.list.d/sogo.list \
-	&& apt-get update \
-	&& apt-get -y --force-yes install sogo sogo-activesync 
+	&& apt-get update && apt-get install -y --force-yes \
+		sogo \
+		sogo-activesync \
+	&& rm -rf /var/lib/apt/lists/*
 
 RUN sed -i -E 's/^(\s*)system\(\);/\1unix-stream("\/dev\/log");/' /etc/syslog-ng/syslog-ng.conf
 RUN echo '* * * * *   sogo   /usr/sbin/sogo-ealarms-notify' > /etc/cron.d/sogo
@@ -42,4 +46,4 @@ COPY supervisord.conf /etc/supervisor/supervisord.conf
 
 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf
 
-RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+RUN rm -rf /tmp/* /var/tmp/*