AEM 6.0 on docker - Dbus connection error - docker

Question

I'm trying to dockerize an AEM 6.0 installation, and this is the Dockerfile for my author.
from centos:latest
COPY aem6.0-author-p4502.jar /AEM/aem/author/aem6.0-author-p4502.jar
COPY license.properties /AEM/aem/author/license.properties
RUN yum install dnsmasq -y
RUN systemctl enable dnsmasq
RUN yum install initscripts -y
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/*;
WORKDIR /AEM/aem/author
RUN yum install wget -y
RUN wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F; oraclelicense=accept-securebackup-cookie" "http://download.oracle.com/otn-pub/java/jdk/8u151-b12/e758a0de34e24606bca991d704f6dcbf/jdk-8u151-linux-x64.rpm"
RUN yum localinstall jdk-8u151-linux-x64.rpm -y
RUN java -XX:MaxPermSize=256m -Xmx512M -jar aem6.0-author-p4502.jar -unpack
COPY aem6 /etc/init.d/aem6
RUN chkconfig --add aem6
RUN yum -y install initscripts && yum update -y & yum clean all
RUN chown -R $USER:$(id -G) /etc/init.d
RUN chmod 777 -R /etc/init.d/aem6
RUN systemctl enable aem6.service
RUN service aem6 start
VOLUME /sys/fs/cgroup
CMD /usr/sbin/init
The build fails on starting the service, with the error - failed to get Dbus connection error. I haven't been able to figure out how to fix it.
I've tried these
- https://github.com/CentOS/sig-cloud-instance-images/issues/45
- https://hub.docker.com/_/centos/

Answer 1

Here, the problem is that you're trying to start the aem service during the "build" phase, with this statement:
RUN service aem6 start
This is problematic for a number of reasons. First, you're building an image. Starting a service at this stage is pointless...when the build process completes, nothing is running. An image is just a collection of files. You don't have any processes until you boot a container, at which point your CMD and ENTRYPOINT influence what is running.
Another problem is that at this stage, nothing else is running inside the container environment. The service command in this case is trying to communicate with systemd using the dbus api, but neither of those services are running.
There is a third slightly more subtle problem: the solution you've chosen relies on systemd, the standard CentOS process manager, and as far as things go you've configured things correctly (by both enabling the service with systemctl enable ... and by starting /sbin/init in your CMD statement). However, running systemd in a container can be tricky, although it is possible. In the past, systemd required the container to run with the --privileged flag; I'm not sure if this is necessary any more.
If you weren't running multiple processes (dnsmasq and aem) inside the container, the simplest solution would be to start the aem service directly, rather than relying on a process manager. This would reduce your Dockerfile to something like:
FROM centos:latest
COPY aem6.0-author-p4502.jar /AEM/aem/author/aem6.0-author-p4502.jar
COPY license.properties /AEM/aem/author/license.properties
WORKDIR /AEM/aem/author
RUN yum install wget -y
RUN wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F; oraclelicense=accept-securebackup-cookie" "http://download.oracle.com/otn-pub/java/jdk/8u151-b12/e758a0de34e24606bca991d704f6dcbf/jdk-8u151-linux-x64.rpm"
RUN yum localinstall jdk-8u151-linux-x64.rpm -y
RUN java -XX:MaxPermSize=256m -Xmx512M -jar aem6.0-author-p4502.jar -unpack
CMD some commandline to start aem
If you actually require dnsmasq, you could run it in a second container (potentially sharing the same network environment as the aem container).