[ 常見問題 ] systemctl - Failed to get D-Bus connection: Operation not permitted

Source From Here
Question
I'm trying to list services on my CentOS image running in Docker using

# systemctl list-units

but I get this error message:

Failed to get D-Bus connection: Operation not permitted

Any suggestions what the problem might be?

How-To
My guess is that you're running a non-privileged container. systemd requires CAP_SYS_ADMIN capability but Docker drops that capability in the non privileged containers, in order to add more security.

systemd also requires RO access to the cgroup file system within a container. You can add it with –v /sys/fs/cgroup:/sys/fs/cgroup:ro So, here a few steps on how to run CentOS with systemd inside a Docker container:

1. Pull centos image
2. Set up a docker file like the one below:

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1. FROM centos  
2. MAINTAINER “Yourname" @address.com>  

ENV container docker  

RUN yum -y update; yum clean all  

RUN yum -y install systemd; yum clean all; \  

(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/*;  

VOLUME [ “/sys/fs/cgroup” ]  

CMD [“/usr/sbin/init”]  

3. Build it - docker build --rm -t centos7-systemd - < mydockerfile
4. Run a container with docker run --privileged -ti -e container=docker -v /sys/fs/cgroup:/sys/fs/cgroup centos7-systemd /usr/sbin/init
5. You should have systemd in your container

If you want an exist docker image to be capable of systemd, you can try "sethrosetter/centos7-systemd-sshd"