Base all on xenial to save some space loading chunks, clean-up images

data/Dockerfiles/dovecot/Dockerfile

@@ -2,22 +2,28 @@ From ubuntu:xenial
 MAINTAINER Andre Peters <andre.peters@servercow.de>
 
 ENV DEBIAN_FRONTEND noninteractive
+ENV LC_ALL C
 
-RUN apt-get update \
-	&& apt-get -y install dovecot-common \
-		dovecot-core \
-		dovecot-imapd \
-		dovecot-lmtpd \
-		dovecot-managesieved \
-		dovecot-sieve \
-		dovecot-mysql \
-		dovecot-pop3d \
-		dovecot-dev \
-		wget \
-		curl \
-		build-essential \
-		autotools-dev \
-		automake
+RUN dpkg-divert --local --rename --add /sbin/initctl \
+    && ln -sf /bin/true /sbin/initctl \
+    && dpkg-divert --local --rename --add /usr/bin/ischroot \
+    && ln -sf /bin/true /usr/bin/ischroot
+
+RUN apt-get update
+RUN apt-get -y install dovecot-common \
+	dovecot-core \
+	dovecot-imapd \
+	dovecot-lmtpd \
+	dovecot-managesieved \
+	dovecot-sieve \
+	dovecot-mysql \
+	dovecot-pop3d \
+	dovecot-dev \
+	wget \
+	curl \
+	build-essential \
+	autotools-dev \
+	automake
 
 WORKDIR /tmp
 RUN wget http://hg.dovecot.org/dovecot-antispam-plugin/archive/tip.tar.gz -O - | tar xvz  \
@@ -31,6 +37,7 @@ COPY ./rspamd-pipe /usr/local/bin/rspamd-pipe
 COPY ./docker-entrypoint.sh /
 
 RUN chmod +x /usr/local/bin/rspamd-pipe
+
 RUN groupadd -g 5000 vmail
 RUN useradd -g vmail -u 5000 vmail -d /var/vmail
 
@@ -38,3 +45,5 @@ EXPOSE 24 10001
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 CMD ["/usr/sbin/dovecot", "-F"]
+
+RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*