Dockerizing Postfix Relay server

Question

I'm trying to build a docker container dedicated to a Postfix SMTP relay. I fail to make it start the postfix service on it after several tries.

Here's the dockerfile

FROM centos:centos7
LABEL Author = "Aurelien HUGON 
LABEL Description = "DOCKERFILE : Creates a Docker Container for a Relay Postfix smtp server"

#Update and soft
RUN yum update -y

RUN yum install -y nano postfix

#Clean install
RUN yum clean all

#Config
COPY /cfg/config.sh /
RUN chmod +x config.sh
RUN ./config.sh
RUN touch /var/log/maillog

CMD ["sh", "-c", "/sbin/postfix start", "tail -f /var/log/maillog"]

The config.sh file contains :

postconf -e 'myhostname = myserverhostname'
postconf -e 'mydomain = domain.com'
postconf -e 'myorigin = $mydomain'
postconf -e 'smtp_generic_maps = hash:/etc/postfix/generic'
postconf -e 'mynetworks = 127.0.0.1/32 192.168.0.0/16 172.16.0.0/12 10.0.0.0/8 [::1]'
postconf -e 'mynetworks_style = class'
postconf -e 'inet_interfaces = all'
postconf -e 'relayhost = [dedicated SMTP server]'
echo "generic@adress.com generic2@adress2.com" > /etc/postfix/generic
postmap /etc/postfix/generic

I tried to use the "postfix start" command as entrypoint in my dockerfile but the container instantly shuts down with return code 0. I tried to start the container with the CMD by removing the /sbin/postfix start part, my container starts and is stable, but i have to start the postfix service manually. And then my relay works. But that's suboptimal.

I found solutions using supervisord, but i want to keep my container as simple as possible. My goal is to have a light interchangeable relay to send my mails from my application hosted on the docker server.

I suggest you look into using this postfix server which runs inside a docker container https://github.com/tomav/docker-mailserver — Scott Stensland, Oct 16 '18 at 22:01

score 5 · Answer 1 · answered Mar 26 '18 at 16:05

5

Postfix v3.3.0 added support for container:

Container support: Postfix 3.3 will run in the foreground with "postfix start-fg".

If you are using a lower version, you might need to use supervisord or an infinite loop or an infinite sleep just to stop the container from exiting.

answered Mar 26 '18 at 16:05

Yuankun

6,875
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Thank you. I will try to dig on this subject. – Aurelien Mar 27 '18 at 08:24
Sorry i couldn't found a repository with Postfix 3.3, the higher i can found is 3.2. – Aurelien Mar 28 '18 at 13:42
@Aurelien the default postfix version on ubuntu 18.04 is 3.3 – Son Jul 12 '19 at 14:34

score 0 · Accepted Answer · answered Mar 29 '18 at 08:54

0

I finally decided to cheat and use Supervisord.

answered Mar 29 '18 at 08:54

Aurelien

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score 0 · Answer 3 · answered Jul 23 '21 at 09:22

0

You could use the following command to start postfix

CMD ["/usr/libexec/postfix/master","-c", "/etc/postfix", "-d"]

answered Jul 23 '21 at 09:22

Naveen Kerati

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Dockerizing Postfix Relay server

3 Answers3