Testing Ansible using Docker

You can test Ansible using Docker containers on your local machine.

First you'll need at least one container acting as a target server e.g. linux with OpenSSH installed.

Secondly you will need another container running Ansible, which will be used to do your testing e.g. run ad-hoc commands and test playbooks.

The images required to create these containers can be built using the Dockerfiles provided (in the "/ubuntu-openssh/" and "/ubuntu-ansible/" directories).

For convenience there are also two public automated builds of these images hosted on Docker Hub, which can be pulled from my account.

Using the images on Docker hub

To create one or more containers running Ubuntu linux (with OpenSSH installed), you can pull down the latest "ubuntu-openssh" image from my account as follows:

docker pull robertbarrow/ubuntu-openssh

e.g.

$ docker pull robertbarrow/ubuntu-openssh
Using default tag: latest
latest: Pulling from robertbarrow/ubuntu-openssh
a48c500ed24e: Already exists
1e1de00ff7e1: Already exists
0330ca45a200: Already exists
471db38bcfbf: Already exists
0b4aba487617: Already exists
4f6fa4f06ac8: Pull complete
699075078b83: Pull complete
ea75ecdd0cd0: Pull complete
2042dc99ad05: Pull complete
9540183f34e3: Pull complete
3c604ffaa258: Pull complete
Digest: sha256:e5ce8bb1f865a93e86317c5925ca05685fa9be6e163084e0ef10f9671a3904e1
Status: Downloaded newer image for robertbarrow/ubuntu-openssh:latest

To create a container with Ansible installed, you can pull down the latest "ansible" image from my account as follows:

docker pull robertbarrow/ansible

e.g.

$ docker pull robertbarrow/ansible
Using default tag: latest
latest: Pulling from robertbarrow/ansible
a48c500ed24e: Already exists
1e1de00ff7e1: Already exists
0330ca45a200: Already exists
471db38bcfbf: Already exists
0b4aba487617: Already exists
d2fb17fa3d79: Pull complete
5e7be7e115b6: Pull complete
ee427dc0889c: Pull complete
1f215fee4d80: Pull complete
Digest: sha256:f6cacdcc1ce18d32833f93744cc5461eb46bc7524965e5acabce839681ef06c5
Status: Downloaded newer image for robertbarrow/ansible:latest

Note: to keep things simple, this image is also running Ubuntu linux.

Now that you have the images, you can create your containers as follows...

Creating Docker containers from the images

To create a detached container running Ubuntu linux with OpenSSH installed:

docker run -d --name ubuntu-server-1 robertbarrow/ubuntu-openssh

e.g.

$ docker run -d --name ubuntu-server-1 robertbarrow/ubuntu-openssh
7e928a0774403d92b616b1280527bbf98241557f3c2c4a1f01c3f225396a4825

Note: the string that gets returned is the full Container ID

To create an interactive container running Ubuntu linux with Ansible installed:

docker run -it --rm robertbarrow/ansible

e.g.

$ docker run -it --rm robertbarrow/ansible
root@aad4dfb5aadf:/# ansible --version
ansible 2.5.3
  config file = None
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python2.7/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 2.7.15rc1 (default, Apr 15 2018, 21:51:34) [GCC 7.3.0]
root@aad4dfb5aadf:/# exit
exit

Note: the -it option provides you with the interactive prompt (via a psuedo TTY session) and the --rm option tells the Docker daemon to decompose the container [i.e. shut it down and remove it] once you've exited your interactive session.

To see which containers are still running

The docker ps command will list the containers that you currently have running e.g.

$ docker ps
CONTAINER ID        IMAGE                         COMMAND               CREATED             STATUS              PORTS               NAMES
7e928a077440        robertbarrow/ubuntu-openssh   "/usr/sbin/sshd -D"   2 minutes ago       Up 2 minutes       22/tcp              ubuntu-server-1

The ubuntu-openssh containers are detached, but still actively running the OpenSSH service [listening on port 22].

Adding the "-a" option (i.e. docker ps -a) will also list any stopped containers e.g.

$ docker ps -a
CONTAINER ID        IMAGE                         COMMAND                  CREATED             STATUS                     PORTS                    NAMES
7e928a077440        robertbarrow/ubuntu-openssh   "/usr/sbin/sshd -D"      17 minutes ago      Up 17 minutes              22/tcp                   ubuntu-server-1
08d93e2796a6        tuned/python-35-rhel7         "container-entrypoint"   7 days ago          Exited (255) 3 hours ago   0.0.0.0:8080->8080/tcp   naughty_galileo

As you can see, the ansible container is still not listed. This is due to the "--rm" option that was used, which deleted the container after you exited from the interactive prompt. The ephemeral nature of the ansible container means that it would only ever be listed by the docker ps command if; (A) you ran it from another session [whilst you were still at the interactive prompt], or (B) if you ran the command as soon as you exited the container and the Docker daemon hadn't finished decomposing it.