Change base image from CentOS 7 to alpine linux

Dockerfile

@@ -1,14 +1,13 @@
 #Dockerfile for a Postfix email relay service
-FROM centos:7
+FROM alpine
 MAINTAINER Juan Luis Baptiste juan.baptiste@gmail.com
 
-RUN yum install -y epel-release && yum update -y && \
-    yum install -y cyrus-sasl cyrus-sasl-plain cyrus-sasl-md5 mailx \
+RUN apk update && \
+    apk add bash gawk cyrus-sasl cyrus-sasl-plain cyrus-sasl-crammd5 mailx \
     perl supervisor postfix rsyslog \
-    && rm -rf /var/cache/yum/* \
-    && yum clean all
-RUN sed -i -e "s/^nodaemon=false/nodaemon=true/" /etc/supervisord.conf
-RUN sed -i -e 's/inet_interfaces = localhost/inet_interfaces = all/g' /etc/postfix/main.cf
+    rm -rf /var/cache/apk/* && \
+    mkdir -p /var/log/supervisor/ /var/run/supervisor/ && \
+    sed -i -e 's/inet_interfaces = localhost/inet_interfaces = all/g' /etc/postfix/main.cf
 
 COPY etc/ /etc/
 COPY run.sh /

docker-compose.dev.yml

@@ -1,6 +1,7 @@
 version: '2'
 services:
   postfix:
+    image: juanluisbaptiste/postfix:dev
     build:
       context: .
       dockerfile: Dockerfile

etc/supervisord.conf

@@ -22,7 +22,7 @@ nodaemon=true              ; (start in foreground if true;default false)
 minfds=1024                 ; (min. avail startup file descriptors;default 1024)
 minprocs=200                ; (min. avail process descriptors;default 200)
 ;umask=022                  ; (process file creation umask;default 022)
-;user=chrism                 ; (default is current user, required if root)
+user=root                 ; (default is current user, required if root)
 ;identifier=supervisor       ; (supervisord identifier, default is 'supervisor')
 ;directory=/tmp              ; (default is not to cd during start)
 ;nocleanup=true              ; (don't clean up tempfiles at start;default false)

run.sh

@@ -44,7 +44,7 @@ if [ ! -f /etc/postfix/sasl_passwd ]; then
   fi
 fi
 
-#Set header tag  
+#Set header tag
 if [ ! -z "${SMTP_HEADER_TAG}" ]; then
   postconf -e "header_checks = regexp:/etc/postfix/header_tag"
   echo -e "/^MIME-Version:/i PREPEND RelayTag: $SMTP_HEADER_TAG\n/^Content-Transfer-Encoding:/i PREPEND RelayTag: $SMTP_HEADER_TAG" > /etc/postfix/header_tag
@@ -70,4 +70,4 @@ add_config_value "mynetworks" "${nets}"
 # starting services
 rm -f /var/spool/postfix/pid/master.pid
 
-exec supervisord
+exec supervisord -c /etc/supervisord.conf