CentOS running with systemd

[ronaldtse]

@drystone as spoken, here's how you enable systemd in a CentOS container.

FROM centos

ENV container docker

# Update yum repos
RUN yum clean expire-cache && yum install -y yum-utils deltarpm && yum upgrade -y

# yum fails on checksums if built on docker host based on overlayfs
# https://github.com/docker/docker/issues/10180
RUN yum install -y yum-plugin-ovl

# elinks and screen for convenience
RUN yum install -y curl sudo tar hostname iproute secure-delete \
    elinks screen \
  && yum clean all

# From https://hub.docker.com/_/centos/
# Dockerfile for systemd base image
# Systemd is now included in both the centos:7 and centos:latest base
# containers, but it is not active by default. In order to use systemd, you
# will need to include text similar to the example Dockerfile below.
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/*;

# We may also want to remove systemd-update-utmp to remove the failures about it
# rm -f /lib/systemd/system/systemd-update-utmp*; \

# FIXME: A RedHat guy's workaround
# https://vpavlin.eu/2015/02/fedora-docker-and-systemd/
# And also from here
RUN systemctl mask systemd-remount-fs.service dev-hugepages.mount \
  sys-fs-fuse-connections.mount systemd-logind.service getty.target \
  console-getty.service
# Unnecessary to mask
# sys-kernel-config.mount sys-kernel-debug.mount systemd-udevd.service

RUN cp /usr/lib/systemd/system/dbus.service /etc/systemd/system/; \
  sed -i 's/OOMScoreAdjust=-900//' /etc/systemd/system/dbus.service

VOLUME ["/sys/fs/cgroup"]

ENTRYPOINT ["/usr/sbin/init"]