postfix-wrapper.sh for supervisord in docker. Controls postfix as it gets controlled by supervisord.

postfix-wrapper.sh

#!/usr/bin/env bash
# postfix-wrapper.sh, version 0.1.0 
#
# You cannot start postfix in some foreground mode and 
# it's more or less important that docker doesn't kill 
# postfix and its chilren if you stop the container.
#
# Use this script with supervisord and it will take 
# care about starting and stopping postfix correctly.
#
# supervisord config snippet for postfix-wrapper:
# 
# [program:postfix]
# process_name = postfix
# command = /path/to/postfix-wrapper.sh
# startsecs = 0
# autorestart = false
# 

trap "postfix stop" SIGINT
trap "postfix stop" SIGTERM
trap "postfix reload" SIGHUP

# force new copy of hosts there (otherwise links could be outdated)
cp /etc/hosts /var/spool/postfix/etc/hosts

# start postfix
postfix start

# lets give postfix some time to start
sleep 3

# wait until postfix is dead (triggered by trap)
while kill -0 "`cat /var/spool/postfix/pid/master.pid`"; do
  sleep 5
done

So, it works with rsyslog.

This is the run script I call

#!/bin/bash

# generate aliases database
newaliases

# Change syslog to local logging and start it
rm -f /etc/rsyslog.d/listen.conf
echo "Starting rsyslogd..."
rsyslogd
sleep 1
echo "rsyslog started"

echo "Starting postfix..."
postfix start
# lets give postfix some time to start
sleep 3
echo "OK running"

tail -F /var/log/maillog

Thanks! I just had to change the test when running on Docker using the alpine postfix, since the PID file have spaces before the actual number.

# Check every 5 seconds if postfix is still alive
PID_FILE="/var/spool/postfix/pid/master.pid"
while true; do
  sleep 5
  # Stop this script if no PID file is available
  if [ ! -f "$PID_FILE" ]; then
    break;
  else
    # Or if the numeric PID in the file can't receive a signal
    PID="$(cat $PID_FILE | sed 's/[^0-9]*//g')"
    if ! kill -0 "$PID" 2>/dev/null; then
      break;
    fi
  fi
done