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docker container can not see the data from a shared volume – CentOS

I’m trying to set up a lab using docker containers with base image centos7 and docker-compose.
Here is my docker-compose.yaml file

version: "3"
services:
  base:
    image: centos_base
    build:
      context: base
  master:
    links:
      - base
    build:
      context: master
    image: centos_master
    container_name: master01
    hostname: master01
    volumes:
      - ansible_vol:/var/ans
    networks:
      - net
  host01:
    links:
      - base
      - master
    build: 
      context: host
    image: centos_host
    container_name: host01
    hostname: host01
    command: ["/var/run.sh"]
    volumes:
     - ansible_vol:/var/ans
    networks:
      - net
networks:
  net:
volumes:
  ansible_vol:

My Docker files are as below

Base Image docker file:

# For centos7.0
FROM centos:7
RUN yum install -y net-tools man vim initscripts openssh-server
RUN echo "12345" | passwd root --stdin
RUN mkdir /root/.ssh

Master Dockerfile :

FROM centos_base:latest
# install ansible package
RUN yum install -y epel-release
RUN yum install -y ansible openssh-clients

RUN mkdir /var/ans
# change working directory
WORKDIR /var/ans

RUN ssh-keygen -t rsa -N 12345 -C "master key" -f master_key

CMD /usr/sbin/sshd -D

Host Image Dockerfile:

FROM centos_base:latest
RUN mkdir /var/ans
COPY run.sh /var/
RUN chmod 755 /var/run.sh

My run.sh file:

#!/bin/bash
cat /var/ans/master_key.pub >> /root/.ssh/authorized_keys
# start SSH server
/usr/sbin/sshd -D

My Problems are:

  1. If I run docker-compose up -d –build, I see no containers coming up. they all getting created but exiting.
Successfully tagged centos_host:latest
Creating working_base_1 ... done
Creating master01       ... done
Creating host01         ... done

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                      PORTS               NAMES
433baf2dd0d8        centos_host         "/var/run.sh"            12 minutes ago      Exited (1) 12 minutes ago                       host01
a2a57e480635        centos_master       "/bin/sh -c '/usr/sb…"   13 minutes ago      Exited (1) 12 minutes ago                       master01
a4acf6fb3e7b        centos_base         "/bin/bash"              13 minutes ago      Exited (0) 13 minutes ago                       working_base_1
  1. ssh keys generated in ‘centos_master’ image are not available in centos_host container, even though I have added a volume mapping ‘ansible_vol:/var/ans’ in docker-compose file
    My intention is these ssh key files generated in master should be available in host containers ,therefore the run.sh script can copy them to authorized_keys section of host containers.

Any help is greatly appreciated.

Tags:

2

Answers


  1. 0

    Try to use external: false, to not attempt the container to create it and override the previous data at creation

    version: "3"
services:
  base:
    image: centos_base
    build:
      context: base
  master:
    links:
      - base
    build:
      context: master
    image: centos_master
    container_name: master01
    hostname: master01
    volumes:
      - ansible_vol:/var/ans
    networks:
      - net
  host01:
    links:
      - base
      - master
    build: 
      context: host
    image: centos_host
    container_name: host01
    hostname: host01
    command: ["/var/run.sh"]
    volumes:
     - ansible_vol:/var/ans
    networks:
      - net
networks:
  net:
volumes:
  ansible_vol:
    external: false
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  2. 0

    Try to put in base/Dockerfile :

    RUN echo "12345" | passwd root --stdin; 
    ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -b 4096 -t rsa

    and rerun docker-compose build

    /etc/ssh/ssh_host_rsa_key is a key used by sshd (ssh daemon), so that containers can be started properly.

    The key you generated and copied into authorized_keys will be used to allow ssh client to connect to container via ssh.

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