Basic docker container files

Dockerfile

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+FROM ubuntu:22.04
+
+ENV DEBIAN_FRONTEND=noninteractive \
+    POSTFIX_OPTS=""
+
+COPY start.sh /start.sh
+RUN apt-get update \
+    && apt-get dist-upgrade -y \
+    && apt-get install -y --no-install-recommends \
+        postfix \
+        swaks \
+        prometheus-postfix-exporter \
+    && rm -rf /var/lib/apt/lists/* \
+    && chmod +x /start.sh
+
+EXPOSE 25
+EXPOSE 587
+
+CMD ["sh", "/start.sh"]

start.sh

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+#!/bin/sh
+
+set -e
+
+mkdir -p /var/spool/postfix
+chown root:root /var/spool/postfix/
+chmod 0755 /var/spool/postfix
+
+mkdir -p \
+    /var/spool/postfix/active \
+    /var/spool/postfix/bounce \
+    /var/spool/postfix/corrupt \
+    /var/spool/postfix/defer \
+    /var/spool/postfix/deferred \
+    /var/spool/postfix/dev \
+    /var/spool/postfix/etc \
+    /var/spool/postfix/flush \
+    /var/spool/postfix/incoming \
+    /var/spool/postfix/lib \
+    /var/spool/postfix/maildrop \
+    /var/spool/postfix/pid \
+    /var/spool/postfix/private \
+    /var/spool/postfix/public \
+    /var/spool/postfix/saved \
+    /var/spool/postfix/usr \
+    /var/spool/postfix/hold \
+    /var/spool/postfix/trace
+
+
+chmod 00700 /var/spool/postfix/active
+chmod 00700 /var/spool/postfix/bounce
+chmod 00700 /var/spool/postfix/corrupt
+chmod 00700 /var/spool/postfix/defer
+chmod 00700 /var/spool/postfix/deferred
+chmod 00755 /var/spool/postfix/dev
+chmod 00755 /var/spool/postfix/etc
+chmod 00700 /var/spool/postfix/flush
+chmod 00700 /var/spool/postfix/incoming
+chmod 00755 /var/spool/postfix/lib
+chmod 01730 /var/spool/postfix/maildrop
+chmod 00755 /var/spool/postfix/pid
+chmod 00700 /var/spool/postfix/private
+chmod 02710 /var/spool/postfix/public
+chmod 00700 /var/spool/postfix/saved
+chmod 00755 /var/spool/postfix/usr
+
+chown -R postfix:postdrop \
+    /var/spool/postfix/maildrop \
+    /var/spool/postfix/public
+
+chown -R postfix:root \
+    /var/spool/postfix/active \
+    /var/spool/postfix/bounce \
+    /var/spool/postfix/corrupt \
+    /var/spool/postfix/defer \
+    /var/spool/postfix/deferred \
+    /var/spool/postfix/flush \
+    /var/spool/postfix/hold \
+    /var/spool/postfix/incoming \
+    /var/spool/postfix/private \
+    /var/spool/postfix/saved \
+    /var/spool/postfix/trace
+
+chown root:root \
+    /var/spool/postfix/dev \
+    /var/spool/postfix/etc \
+    /var/spool/postfix/lib \
+    /var/spool/postfix/pid \
+    /var/spool/postfix/usr
+
+cp /etc/host.conf \
+    /etc/hosts \
+    /etc/nsswitch.conf \
+    /etc/resolv.conf \
+    /etc/services \
+    /var/spool/postfix/etc
+
+exec postfix start-fg $POSTFIX_OPTS