Error while trying to ssh a docker container : System is booting up

Question

I am trying to build an image and run container as an ssh server. I want to be able to ssh that container (remote_host) from another container (jenkins/jenkins)

I am using a VM with Centos.

I am using this docker file. I run it from my VM host machine(Centos too)

FROM centos

RUN yum -y install openssh-server openssh-clients

RUN useradd -ms /bin/bash remote_user && \
  echo 'remote_user:12345' | chpasswd && \
  mkdir /home/remote_user/.ssh && \
  chmod 700 /home/remote_user/.ssh

COPY remote-key.pub /home/remote_user/.ssh/authorized_keys

RUN chown remote_user:remote_user -R /home/remote_user/.ssh && \
    chmod 600 /home/remote_user/.ssh/authorized_keys

EXPOSE 22
RUN /usr/bin/ssh-keygen -A
CMD ["/usr/sbin/sshd", "-D"]

My docker compose file

---
networks:
  net: ~
services:
  jenkins:
    container_name: jenkins
    image: jenkins/jenkins
    networks:
      - net
    ports:
      - "8080:8080"
    volumes:
      - "$PWD/jenkins_home:/var/jenkins_home"
  remote_host:
    container_name: remote-host
    image: remote-host
    build:
      context: centos7
    networks:
      - net
version: "3"

I run docker-compose build from my host machine

Building remote_host
Step 1/8 : FROM centos
 ---> 0f3e07c0138f
Step 2/8 : RUN yum -y install openssh-server openssh-clients
 ---> Using cache
 ---> 277411f7cc41
Step 3/8 : RUN useradd -ms /bin/bash remote_user &&   echo 'remote_user:12345' | chpasswd &&   mkdir /home/remote_user/.ssh &&   chmod 700 /home/remote_user/.ssh
 ---> Using cache
 ---> c42b15de9da7
Step 4/8 : COPY remote-key.pub /home/remote_user/.ssh/authorized_keys
 ---> Using cache
 ---> f205521e83cb
Step 5/8 : RUN chown remote_user:remote_user -R /home/remote_user/.ssh &&     chmod 600 /home/remote_user/.ssh/authorized_keys
 ---> Using cache
 ---> a7bb438b87ed
Step 6/8 : EXPOSE 22
 ---> Using cache
 ---> 7f28ef8e4ec9
Step 7/8 : RUN /usr/bin/ssh-keygen -A
 ---> Using cache
 ---> a4fae9730627
Step 8/8 : CMD ["/usr/sbin/sshd", "-D"]
 ---> Using cache
 ---> 3fe69c9789a6
Successfully built 3fe69c9789a6
Successfully tagged remote-host:latest

Then I run docker-compose up -d

docker ps give me :

0f9987444fcf        remote-host         "/usr/sbin/sshd -D"      28 minutes ago      Up 16 minutes       22/tcp                              remote-host
4c9ba830f419        jenkins/jenkins     "/sbin/tini -- /usr/…"   7 hours ago         Up 7 hours          0.0.0.0:8080->8080/tcp, 50000/tcp   jenkins 

I ssh my first container:

docker exec -it jenkins bash

Then When I try to ssh the second container from the first one

ssh remote_user@remote_host

I got this error

Are you sure you want to continue connecting (yes/no)?
remote_user@remote_host's password:12345
"System is booting up. Unprivileged users are not permitted to log in yet. Please come back later. For technical details, see pam_nologin(8)."
Authentication failed.

Answer 1

Solution:

Please edit your dockerfile like this:

FROM centos
RUN yum -y install openssh-server
RUN useradd remote_user && \
    echo remote_user:1234 | chpasswd && \
    mkdir /home/remote_user/.ssh && \
    chmod 700 /home/remote_user/.ssh
COPY remote-key.pub /home/remote_user/.ssh/authorized_keys
RUN chown remote_user:remote_user -R /home/remote_user/.ssh && \
    chmod 600 /home/remote_user/.ssh/authorized_keys
RUN /usr/bin/ssh-keygen -A
EXPOSE 22
RUN rm -rf /run/nologin
CMD /usr/sbin/sshd -D

Answer 2

If the remote_host is not in the process of booting then log into the remote_host, become root and remove /run/nologin file.