viklund/centos-devbox repository overview

⁠centos-devbox

Docker Image of CentOS-6 6.5 x86_64, expanded with SSH and basic development stuff.

This image is a slightly modified version of jdeathe/centos-ssh⁠.

The Dockerfile can be used to build a base image that is the bases for several other docker images.

Included in the build is the EPEL repository and SSH, vi and are installed along with python-pip, supervisor and supervisor-stdout.

Supervisor⁠ is used to start and the sshd daemon when a docker container based on this image is run. To enable simple viewing of stdout for the sshd subprocess, supervisor-stdout is included. This allows you to see output from the supervisord controlled subprocesses with docker logs <docker-container-name>.

SSH access is by public key authentication and, by default, the Vagrant⁠ insecure private key⁠ is required.

⁠Quick Example

Run up a container named 'ssh.pool-1.1.1' from the docker image 'viklund/centos-devbox' on port 2020 of your docker host.

$ docker run -d \
  --name ssh.pool-1.1.1 \
  -p 2020:22 \
  viklund/centos-devbox:latest

⁠Instructions

⁠(Optional) Configuration Data Volume

Create a "data volume" for configuration, this allows you to share the same configuration between multiple docker containers and, by mounting a host directory into the data volume you can override the default configuration files provided.

Make a directory on the docker host for storing container configuration files. This directory needs to contain at least the following files:

• authorized_keys
• ssh-bootstrap.conf
• sshd_config

$ mkdir -p /etc/services-config/ssh.pool-1

Create the data volume, mounting our docker host's configuration directory to /etc/services-config/ssh in the docker container. Note that docker will pull the busybox:latest image if you don't already have available locally.

$ docker run \
  --name volume-config.ssh.pool-1.1.1 \
  -v /etc/services-config/ssh.pool-1:/etc/services-config/ssh \
  busybox:latest \
  /bin/true

⁠Running

To run the a docker container from this image you can use the included run.sh and run.conf scripts. The helper script will stop any running container of the same name, remove it and run a new daemonised container on an unspecified host port. Alternatively you can use the following.

$ docker stop ssh.pool-1.1.1 \
  && docker rm ssh.pool-1.1.1 \
  ; docker run -d \
  --name ssh.pool-1.1.1 \
  -p :22 \
  --volumes-from volume-config.ssh.pool-1.1.1 \
  viklund/centos-devbox:latest

Now you can find out the app-admin, (sudoer), user's password by inspecting the container's logs

$ docker logs ssh.pool-1.1.1

The output of the logs should show the auto-generated password for the app-admin and root users, (if not try again after a few seconds).

sshd_bootstrap stdout | Initialise SSH...
sshd_bootstrap stdout |
--------------------------------------------------------------------------------
SSH Credentials:
root : ut5vZhb5
app-admin : s4pjZwT8
--------------------------------------------------------------------------------

2014-07-05 19:35:35,370 INFO exited: sshd_bootstrap (exit status 0; expected)

⁠Connect to the running container using SSH

If you have not already got one, create the .ssh directory in your home directory with the permissions required by SSH.

$ mkdir -pm 700 ~/.ssh

Get the Vagrant⁠ insecure public key using curl (you could also use wget if you have that installed).

$ curl -LsSO https://raw.githubusercontent.com/mitchellh/vagrant/master/keys/vagrant && \
  mv vagrant ~/.ssh/id_rsa_insecure && \
  chmod 600 ~/.ssh/id_rsa_insecure

If the command ran successfully you should now have a new private SSH key installed in your home "~/.ssh" directory called "id_rsa_insecure"

Next, unless we specified one, we need to determine what port to connect to on the docker host. You can do this with ether docker ps or docker inspect. In the following example we use docker ps to show the list of running containers and pipe to grep to filter out the host port.

$ docker ps | \
  grep ssh.pool-1.1.1 | \
  grep -oe ':[0-9]*->22\/tcp' | \
  grep -oe ':[0-9]*' | \
  cut -c 2-

To connect to the running container use:

$ ssh -p <container-port> -i ~/.ssh/id_rsa_insecure \
  app-admin@<docker-host-ip> \
  -o StrictHostKeyChecking=no

⁠Custom Configuration

If using the optional data volume for container configuration you are able to customise the configuration. In the following examples your custom docker configuration files should be located on the Docker host under the directory /etc/service-config/<container-name>/ where <container-name> should match the applicable container name such as "ssh.pool-1.1.1" or, if the configuration is common across a group of containers, simply "ssh.pool-1" for the given examples.

⁠ssh/authorized_keys⁠

The supplied insecure private key is for demonstration/review purposes only. You should create your own private key if you don't already have one using the following command; pressing the enter key when asked for a passphrase to prevent you being prompted for a passphrase.

$ ssh-keygen -q -t rsa -f ~/.ssh/id_rsa

You should now have an SSH public key, (~/.ssh/id_rsa.pub), that can be used to replace the default one in your custom authorized_keys file.

The following example shows how to copy your file to a remote docker host:

$ scp ~/.ssh/id_rsa.pub \
  <docker-host-user>@<docker-host-ip>:/etc/services-config/ssh.pool-1/authorized_keys

⁠ssh/ssh-bootstrap.conf⁠

The bootstrap script sets up the sudo user and generates a random 8 character password you can override this behavior by supplying your own values in your custom ssh-bootstrap.conf file. You can also change the sudoer username to something other that the default "app-admin".

⁠ssh/sshd_config⁠

The SSH daemon options can be overriden with your custom sshd_config file.

⁠supervisor/supervisord.conf⁠

The supervisor service's configuration can also be overriden by editing the custom supervisord.conf file. It shouldn't be necessary to change the existing configuration here but you could include more [program:x] sections to run additional commands at startup.