docker container can not see the data from a shared volume - linux

Question

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:
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
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.

Answer 1

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.

Answer 2

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