Start sshd automatically with docker container

Question 1

You can try a more elegant way to do that with phusion/baseimage-docker

https://github.com/phusion/baseimage-docker#readme

Question 2

Just try:

ENTRYPOINT service ssh restart && bash

in your dockerfile, it works fun for me!

more details here: How to automatically start a service when running a docker container?

Question 3

Here is a Dockerfile which installs ssh server and runs it:

# Build Ubuntu image with base functionality.
FROM ubuntu:focal AS ubuntu-base
ENV DEBIAN_FRONTEND noninteractive
SHELL ["/bin/bash", "-o", "pipefail", "-c"]

# Setup the default user.
RUN useradd -rm -d /home/ubuntu -s /bin/bash -g root -G sudo ubuntu
RUN echo 'ubuntu:ubuntu' | chpasswd
USER ubuntu
WORKDIR /home/ubuntu

# Build image with Python and SSHD.
FROM ubuntu-base AS ubuntu-with-sshd
USER root

# Install required tools.
RUN apt-get -qq update \
    && apt-get -qq --no-install-recommends install vim-tiny=2:8.1.* \
    && apt-get -qq --no-install-recommends install sudo=1.8.* \
    && apt-get -qq --no-install-recommends install python3-pip=20.0.* \
    && apt-get -qq --no-install-recommends install openssh-server=1:8.* \
    && apt-get -qq clean    \
    && rm -rf /var/lib/apt/lists/*

# Configure SSHD.
# SSH login fix. Otherwise user is kicked off after login
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd
RUN mkdir /var/run/sshd
RUN bash -c 'install -m755 <(printf "#!/bin/sh\nexit 0") /usr/sbin/policy-rc.d'
RUN ex +'%s/^#\zeListenAddress/\1/g' -scwq /etc/ssh/sshd_config
RUN ex +'%s/^#\zeHostKey .*ssh_host_.*_key/\1/g' -scwq /etc/ssh/sshd_config
RUN RUNLEVEL=1 dpkg-reconfigure openssh-server
RUN ssh-keygen -A -v
RUN update-rc.d ssh defaults

# Configure sudo.
RUN ex +"%s/^%sudo.*$/%sudo ALL=(ALL:ALL) NOPASSWD:ALL/g" -scwq! /etc/sudoers

# Generate and configure user keys.
USER ubuntu
RUN ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519
#COPY --chown=ubuntu:root "./files/authorized_keys" /home/ubuntu/.ssh/authorized_keys

# Setup default command and/or parameters.
EXPOSE 22
CMD ["/usr/bin/sudo", "/usr/sbin/sshd", "-D", "-o", "ListenAddress=0.0.0.0"]

Build with the following command:

docker build --target ubuntu-with-sshd -t ubuntu-with-sshd .

Then run with:

docker run -p 2222:22 ubuntu-with-sshd

To connect to container via local port, run: ssh -v localhost -p 2222.

To check for container IP address, use docker ps and docker inspect.

Here is example of docker-compose.yml file:

---
version: '3.4'
services:
  ubuntu-with-sshd:
    image: "ubuntu-with-sshd:latest"
    build:
      context: "."
      target: "ubuntu-with-sshd"
    networks:
      mynet:
        ipv4_address: 172.16.128.2
    ports:
      - "2222:22"
    privileged: true # Required for /usr/sbin/init
networks:
  mynet:
    ipam:
      config:
        - subnet: 172.16.128.0/24

To run, type:

docker-compose up --build

Question 4

I think the correct way to do it would follow docker's instructions to dockerizing the ssh service.

And in correlation to the specific question, the following lines added at the end of the dockerfile will achieve what you were looking for:

EXPOSE 22
CMD ["/usr/sbin/sshd", "-D"]

Dockerize a SSHD service

Question 5

I have created dockerfiler to run ssh inside. I think it is not secure, but for testing/development in DMZ it could be ok:

FROM ubuntu:20.04

USER root

# change root password to `ubuntu`
RUN echo 'root:ubuntu' | chpasswd

ENV DEBIAN_FRONTEND noninteractive

# install ssh server
RUN apt-get update && apt-get install -y \
  openssh-server sudo \
  && rm -rf /var/lib/apt/lists/*

# workdir for ssh
RUN mkdir -p /run/sshd

# generate server keys
RUN ssh-keygen -A

# allow root to login
RUN sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/g' /etc/ssh/sshd_config

EXPOSE 22

# run ssh server
CMD ["/usr/sbin/sshd", "-D", "-o", "ListenAddress=0.0.0.0"]

Question 6

You can start ssh server when starting your container probably. Something like this:

docker run ubuntu /usr/sbin/sshd -D

Check out this official tutorial.

Question 7

This is what I did:

FROM nginx

# install gosu
# seealso:
# https://docs.docker.com/develop/develop-images/dockerfile_best-practices/
# https://github.com/tianon/gosu/blob/master/INSTALL.md
# https://github.com/tianon/gosu
RUN set -eux; \
    apt-get update; \
    apt-get install -y gosu; \
    rm -rf /var/lib/apt/lists/*; \
# verify that the binary works
    gosu nobody true

ENV myenv='default'

RUN apt-get update && apt-get install -y openssh-server
RUN mkdir /var/run/sshd

COPY entrypoint.sh /entrypoint.sh

ENV AIRFLOW_HOME=/usr/local/airflow
RUN mkdir $AIRFLOW_HOME
RUN groupadd --gid 8080 airflow
RUN useradd --uid 8080 --gid 8080 -ms /bin/bash -d $AIRFLOW_HOME airflow
RUN echo 'airflow:mypass' | chpasswd


EXPOSE 22
CMD ["/entrypoint.sh"]

Inside entrypoint.sh:

echo "starting ssh as root"
gosu root service ssh start &
#gosu root /usr/sbin/sshd -D &

echo "starting tail user"
exec gosu airflow tail -f /dev/null

Question 8

Well, I used the following command to solve that

docker run -i -t  mycentos6 /bin/bash -c '/etc/init.d/sshd start && /bin/bash'

Question 9

First login to your container and write an initialization script /bin/init as following:

# execute in the container
cat <<EOT >> /bin/init
#!/bin/bash
service ssh start
while true; do sleep 1; done
EOT

Then make the root user is permitted to logging via ssh:

# execute in the container
echo "PermitRootLogin yes" >> /etc/ssh/sshd_config

Commit the container to a new image after exiting from the container:

# execute in the server
docker commit <YOUR_CONTAINER> <ANY_REPO>:<ANY_TAG>

From now on, as long as you run your container with the following command, the ssh service will be automatically started.

# execute in the server
docker run -it -d --name <NAME> <REPO>:<TAG> /bin/init
docker exec -it <NAME> /bin/bash

Done.