FROM debian:bookworm-slim

RUN set -eux && \
    apt-get update && \
    DEBIAN_FRONTEND=noninteractive apt-get upgrade -y && \
    DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
        openssh-server \
        curl \
        telnet \
        net-tools \
        screen \
    && \
    rm -rf /var/lib/apt/lists/* && \
    rm /etc/ssh/ssh_host_*key*

ADD start.sh /

EXPOSE 22/tcp

CMD /start.sh

HEALTHCHECK CMD netstat -tnlp | grep '0.0.0.0:22' || exit 1