configure docker variables with ansible - docker

Question

I have a docker image for an FTP server in a repository, this image will be used for several machines, I need to deploy container and change PORT variable depending on the destination machine.
This is my image (I've deleted lines for proftpd installation cause it is not relevant to this case):
FROM alpine:3.5
ARG vcs_ref="Unknown"
ARG build_date="Unknown"
ARG build_number="1"
LABEL org.label-schema.vcs-ref=$vcs_ref \
org.label-schema.build-date=$build_date \
org.label-schema.version="alpine-r${build_number}"
ENV PORT=10000
COPY assets/port.conf /usr/local/etc/ports.conf
COPY replace.sh /replace.sh
#It is for a proFTPD Server
CMD ["/replace.sh"]
My port.conf file (Also deleted not relevant information for this case)
# This is a basic ProFTPD configuration file (rename it to
# 'proftpd.conf' for actual use. It establishes a single server
# and a single anonymous login. It assumes that you have a user/group
# "nobody" and "ftp" for normal operation and anon.
ServerName "ProFTPD Default Installation"
ServerType standalone
DefaultServer on
# Port 21 is the standard FTP port.
Port {{PORT}}
.
.
.
And replace.sh script is:
#!/bin/bash
set -e
[ -z "${PORT}" ] && echo >&2 "PORT is not set" && exit 1
sed -i "s#{{PORT}}#$PORT#g" /usr/local/etc/ports.conf
/usr/local/sbin/proftpd -n -c /usr/local/etc/proftpd.conf
... Is there any way to avoid using replace.sh and use ansible as the one who replace PORT variable in /usr/local/etc/proftpd.conf the file inside the container?
My actual ansible script for container is:
- name: (ftpd) Run container
docker_container:
name: "myimagename"
image: "myimage"
state: present
pull: true
restart_policy: always
env:
"PORT": "{{ myportUsingAnsible}}"
networks:
- name: "{{ network }}"
Resuming all that I need is to use Ansible to replace configuration variable instead of using a shell script that replaces variables before running services, is it possible?
Many thanks

Answer 1

You are using the docker_container module which will need a pre-built image. The file port.conf is baked inside the image. What you need to do is set a static port inside this file. Inside the container, you always use
the static port 21 and depending on the machine, you map this port onto a different port using ansible.
Inside port.conf always use port 21
# Port 21 is the standard FTP port.
Port 21
The ansible task would look like:
- name: (ftpd) Run container
docker_container:
name: "myimagename"
image: "myimage"
state: present
pull: true
restart_policy: always
networks:
- name: "{{ network }}"
ports:
- "{{myportUsingAnsible}}:21"
Now when you connect to the container, you need to use the <hostnamne>:{{myportUsingAnsible}}. This is the standard docker way of doing things. The port inside the image is static and you change the port mappings based on the
available ports that you have.