Starting Gunicorn Service in Dockerfile : Failed to get D-Bus connection: Operation not permitted - docker

Question

I m trying to start services(gunicorn, nginx) with my dockerfile but I got that error.
This is my dockerfile
FROM centos:centos7
RUN yum -y install epel-release
RUN yum -y --enablerepo=base clean metadata
RUN yum -y install nginx
RUN yum -y install python-pip
RUN pip install --upgrade pip
RUN yum -y install systemd;
RUN yum clean all;
COPY . /
RUN pip install --no-cache-dir -r requirements.txt
RUN ./manage.py makemigrations
RUN ./manage.py migrate
ENV container docker
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i == \
systemd-tmpfiles-setup.service ] || rm -f $i; done); \
rm -f /lib/systemd/system/multi-user.target.wants/*;\
rm -f /etc/systemd/system/*.wants/*;\
rm -f /lib/systemd/system/local-fs.target.wants/*; \
rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
rm -f /lib/systemd/system/basic.target.wants/*;\
rm -f /lib/systemd/system/anaconda.target.wants/*;
#Gunicorn
RUN cp gunicorn_systemd /etc/systemd/system/gunicorn.service
RUN systemctl start gunicorn
RUN systemctl enable gunicorn
And this is my build command
docker build -t guni ./
Any help please ?

Answer 1

You are trying to interact with systemd in your build script:
RUN systemctl start gunicorn
There are a number of problems here. First, trying to "start" a service as part of the build process doesn't make any sense: you're building an image, not starting a container.
Secondly, you're trying to interact with systemd, but you're never starting systemd, and it is unlikely that you want to [1]. Since a docker container is typically a "single process" environment, you don't need any init-like process supervisor to start things for you. You just need to arrange to run the necessary command yourself.
Taking Apache httpd as an example, rather than running:
systemctl start httpd
You would run:
httpd -DFOREGROUND
This runs the webserver and ensures that it stays in the foreground (the Docker container will exit when the foreground process exits). You can surely do something similar with gunicorn.
Your container is also missing a CMD or ENTRYPOINT directive, so it's not going to do anything when you run it unless you provide an explicit command, and that's probably not the behavior you want.
[1] If you really think you need systemd, you would need to arrange to start it when the container starts (e.g, CMD /sbin/init), but systemd is not something that runs well in an unprivileged container environment. It's possible but I wouldn't recommend it.