Dockerfile

FROM ubuntu:focal

ENV LC_ALL C
ENV DEBIAN_FRONTEND noninteractive

RUN apt-get update \
    && apt-get install -y --no-install-recommends systemd python3 sudo bash net-tools openssh-server openssh-client vim git\
    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
RUN sed -i 's/#PermitRootLogin/PermitRootLogin/' /etc/ssh/sshd_config
RUN sed -i 's/#PubkeyAuthentication yes/PubkeyAuthentication yes/' /etc/ssh/sshd_config
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd
RUN rm -f /lib/systemd/system/multi-user.target.wants/* \
    /etc/systemd/system/*.wants/* \
    /lib/systemd/system/local-fs.target.wants/* \
    /lib/systemd/system/sockets.target.wants/*udev* \
    /lib/systemd/system/sockets.target.wants/*initctl* \
    /lib/systemd/system/sysinit.target.wants/systemd-tmpfiles-setup* \
    /lib/systemd/system/systemd-update-utmp*

RUN ln -s /lib/systemd/system /sbin/init
RUN systemctl set-default multi-user.target
#set password to "password"
RUN sed -i 's#root:\*#root:sa3tHJ3/KuYvI#' /etc/shadow
ENV init /lib/systemd/systemd
VOLUME [ "/sys/fs/cgroup" ]

ENTRYPOINT ["/lib/systemd/systemd"]