This is a systemd enabled centos7 image:
https://hub.docker.com/_/centos/
To run for testing:
#If /sys/fs/cgroup/systemd exists: docker run -it --cap-add SYS_ADMIN --security-opt seccomp:unconfined -v /sys/fs/cgroup:/sys/fs/cgroup:ro -v /tmp/$(mktemp -d):/run --name docker-centos7-systemd cmconner156/docker-centos7-systemd /usr/sbin/init
#If it does not exist docker run -it --cap-add SYS_ADMIN --security-opt seccomp:unconfined -v /tmp/$(mktemp -d):/run --name docker-centos7-systemd cmconner156/docker-centos7-systemd /usr/sbin/init