Automate Building your Own Atomic Host

Project Atomic hosts are built from standard RPM packages which have been composed into filesystem trees using rpm-ostree. This post provides method for automation of Building Atomic host (Creating new trees).



Clone the Git repo on your working machine Build-Atomic-Host.

$ git clone
$ cd build-atomic-host

Create VM from the QCOW2 Image

The following creates VM from QCOW2 Image where username is atomic-user and password is atomic. Here atomic-nodein the instance name.

$ sudo sh atomic-node /path/to/fedora-atomic25.qcow2
# For example: /var/lib/libvirt/images/Fedora-Atomic-25-20170131.0.x86_64.qcow2

Start HTTP Server

The tree is made available via web server. The following playbook creates directory structure, initializes OSTree repository and starts the HTTP server.

$ ansible-playbook httpserver.yml --ask-sudo-pass

Use ip addr to check IP Address of the HTTP server.

Give OSTree a name and add HTTP Server IP Address

Replace the variables given in vars/atomic.yml with OSTree name and HTTP Server IP Address.

For Instance:

# Variables for Atomic host
atomicname: my-atomic

Here my-atomic is OSTree name and is HTTP Server IP Address.

Run Main Playbook

The following playbook installs requirements, starts HTTP Server, composes OSTree, performs SSH-setup and rebases on created Tree.

$ ansible-playbook main.yml --ask-sudo-pass

Check IP Address of the Atomic instance

The following command returns the IP Address of the running Atomic instance

$ sudo virsh domifaddr atomic-node


Now SSH to the Atomic Host and reboot it so that it can reboot in to the created OSTree:

$ ssh atomic-user@<atomic-hostIP>
$ sudo systemctl reboot

Verify: SSH to the Atomic Host

Wait for 10 minutes, You may want to go for a Coffee now.

$ ssh atomic-user@
[atomic-user@atomic-node ~]$ sudo rpm-ostree status
State: idle
● my-atomic:fedora-atomic/25/x86_64/docker-host
       Version: 25.1 (2017-02-07 05:34:46)
        Commit: 15b70198b8ec7fd54271f9672578544ff03d1f61df8d7f0fa262ff7519438eb6
        OSName: fedora-atomic

       Version: 25.51 (2017-01-30 20:09:59)
        Commit: f294635a1dc62d9ae52151a5fa897085cac8eaa601c52e9a4bc376e9ecee11dd
        OSName: fedora-atomic

Now you have the Updated Tree.

Shout-Out for the following folks:

My future post will have customizing packages (includes addition/deletion) for OSTree.

Talking to Docker daemon of Fedora Atomic Host

This post is now deprecated, Please follow the more enhanced one:

This post will describe how to use Docker daemon of Fedora Atomic host remotely.  Note that we are also going to secure the Docker daemon since we are connecting via Network which we will be doing with TLS.

TLS (Transport Layer Security) provides communication security over computer network. We will create client cert and server cert to secure our Docker daemon. OpenSSL will be used to to create the cert keys for establishing TLS connection.

I am using Fedora Atomic host as remote and workstation as my present host.

Thanks to Chris Houseknecht for writing an Ansible role which creates all the certs required automatically, so that there is no need to issue openssl commands manually. Here is the Ansible role repository: Clone it to your present working host.

$ mkdir secure-docker-daemon
$ cd secure-docker-daemon
$ git clone
$ touch ansible.cfg inventory secure-docker-daemon.yml
$ ls 
ansible.cfg  inventory  role-secure-docker-daemon  secure-docker-daemon.yml

$ vim ansible.cfg

$ vim inventory 
'IP_OF_ATOMIC_HOST' ansible_ssh_private_key_file='PRIVATE_KEY_FILE'

$ vim secure-docker-daemon.yml
- name: Secure Docker daemon for Atomic host
  hosts: serveratomic
  gather_facts: no
  become: yes
    - role: role-secure-docker-daemon
      dds_host: 'IP_OF_ATOMIC_HOST'
      dds_server_cert_path: /etc/docker
      dds_restart_docker: no

Replace ‘USER_OF_ATOMIC_HOST’ with the user of your Atomic host, ‘IP_OF_ATOMIC_HOST’ with the IP of your Atomic host, ‘PRIVATE_KEY_FILE’ with the ssh private key file of your workstation.

Now we will run the ansible playbook. This will create client and server certs on the Atomic host.

$ ansible-playbook secure-docker-daemon.yml

Now ssh to your Atomic host.

We will copy the client certs created on the Atomic host to the workstation. You will find the client certs file in ~/.docker directory as root user. Now create ~/.docker directory on your workstation for regular user and copy the client certs there. You can use scp to copy the cert files from Atomic host to Workstation or do it manually ;-).

We are going to append some Environment variables in the ~/.bashrc file of the workstation for regular user.

$ vim ~/.bashrc
export DOCKER_CERT_PATH=~/.docker/

Docker’s port is 2376 for TLS (secured port).

Now go your Atomic host. We will add tls options to docker command on atomic host.

Add –tlsverify –tlscacert=/etc/docker/ca.pem –tlscert=/etc/docker/server-cert.pem –tlskey=/etc/docker/server-key.pem -H= -H=unix:///var/run/docker.sock in the /etc/sysconfig/docker file.

$ vi /etc/sysconfig/docker
OPTIONS='--selinux-enabled --log-driver=journald --tlsverify --tlscacert=/etc/docker/ca.pem --tlscert=/etc/docker/server-cert.pem --tlskey=/etc/docker/server-key.pem -H= -H=unix:///var/run/docker.sock'

We will need to reload and restart the docker daemon.

$ sudo systemctl docker-reload
$ sudo systemctl restart docker.service

Reboot both of your Atomic host and Workstation.

So now if you try running any docker command as regular user on your workstation it will talk to the docker daemon of the Atomic host and execute the command there. You do not need to manually ssh and issue docker command on your Atomic host :-).

Here are some screenshots for demonstration:

Atomic Host:








Containerization and Deployment of Application on Atomic Host using Ansible Playbook

This article describes how to build Docker image and deploy containerized application on Atomic host (any Remote host) using Ansible Playbook.

Building Docker image for an application and run container/cluster of containers is nothing new. But the idea is to automate the whole process and this is where Ansible playbooks come in to play.

Note that you can use Cloud/Workstation based Image to execute the following task. Here I am issuing the commands on Fedora Workstation.

Let’s see How to automate the containerization and deployment process for a simple Flask application:

We are going to deploy container on Fedora Atomic host.

First, Let’s Create a simple Flask Hello-World Application.

This is the Directory structure of the entire Application:

├── ansible
│   ├── ansible.cfg
│   ├── inventory
│   └── main.yml
├── Dockerfile
└── flask-helloworld
    ├── static
    │   └── style.css
    └── templates
        ├── index.html
        └── master.html

from flask import Flask, render_template

APP = Flask(__name__)

def index():
    return render_template('index.html')

if __name__ == '__main__':, host='')


body {
  background: #F8A434;
  font-family: 'Lato', sans-serif;
  color: #FDFCFB;
  text-align: center;
  position: relative;
  bottom: 35px;
  top: 65px;
.description {
  position: relative;
  top: 55px;
  font-size: 50px;
  letter-spacing: 1.5px;
  line-height: 1.3em;
  margin: -2px 0 45px;


<!doctype html>
    {% block head %}
    <title>{% block title %}{% endblock %}</title>
    {% endblock %}
    												<link rel="stylesheet" href="" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" crossorigin="anonymous">
    												<link href="" rel="stylesheet" integrity="sha384-T8Gy5hrqNKT+hzMclPo118YTQO6cYprQmhrYwIiQ/3axmI1hQomh7Ud2hPOy8SP1" crossorigin="anonymous">
    												<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
    												<link href=',700' rel='stylesheet' type='text/css'>

<div id="container">
    {% block content %}
    {% endblock %}</div>


{% extends "master.html" %}

{% block title %}Welcome to Flask App{% endblock %}

{% block content %}
<div class="description">

Hello World</div>
{% endblock %}

Let’s write the Dockerfile.

FROM fedora
MAINTAINER Trishna Guha<>

RUN dnf -y update && dnf -y install python-flask python-jinja2 && dnf clean all
RUN mkdir -p /app

COPY files/ /app/

ENTRYPOINT ["python"]
CMD [""]

Now we will work on Ansible playbook for our application that deals with the automation part:

Create inventory file:

IP_ADDRESS_OF_HOST ansible_ssh_private_key_file=<'PRIVATE_KEY_FILE'>

Replace IP_ADDRESS_OF_HOST with the IP address of the atomic/remote host and ‘PRIVATE_KEY_FILE’ with your private key file.

Create ansible.cfg file:



Replace USER with the user of your remote host.

Create main.yml file:

- name: Deploy Flask App
  hosts: atomic
  become: yes

    src_dir: [Source Directory]
    dest_dir: [Destination Directory]

    - name: Create Destination Directory
       path: "{{ dest_dir }}/files"
       state: directory
       recurse: yes

    - name: Copy Dockerfile to host
       src: "{{ src_dir }}/Dockerfile"
       dest: "{{ dest_dir }}"

    - name: Copy Application to host
       src: "{{ src_dir }}/flask-helloworld/"
       dest: "{{ dest_dir }}/files/"

    - name: Make sure that the current directory is {{ dest_dir }}
      command: cd {{ dest_dir }}

    - name: Build Docker Image
      command: docker build --rm -t fedora/flask-app:test -f "{{ dest_dir }}/Dockerfile" "{{ dest_dir }}"

    - name: Run Docker Container
      command: docker run -d --name helloworld -p 5000:5000 fedora/flask-app:test

Replace [Source Directory] in src_dir field in main.yml with your /path/to/src_dir of your current host.

Replace [Destination Directory] in dest_dir field in main.yml with your /path/to/dest_dir of your remote atomic host.

Now simply run $ ansible-playbook main.yml :).  To verify if the application is running issue this command $ curl http://localhost:5000 on your atomic/remote host.

You can also manage your containers running on remote host using Cockpit. Check this article to know how to use Cockpit to manage your containers:



Here is the repository of the above example:

My future post will be related to ansible-container where I will describe how we can build Docker image and orchestrate container without writing any Dockerfile :).


What is if __name__ == ‘__main__’ ?


Module is simply Python file that has .py extension. Module can contain variables, functions, classes that can be reused.

In order to use module we need to import the module using import command. Check the full list of built-in modules in Python here

The first time a module is loaded in to running Python script, it is initialized by executing the code in the module once. To know various ways of importing modules visit here:

if __name__ == ‘__main__’:

We see if __name__ == ‘__main__’: quite often. Let’s see what this actually is.

__name__ is global variable in Python that exists in all namespaces. It is attribute of module. It is basically the name of the module as str (string) type.

Show Me Code:

Create a file named ‘’ and type the following code and save it. We have defined a simple mathematical square method here.


Now create another file named ‘’ in the same directory and type the following code and save it.


Now on terminal run the program with ‘python3’

Here we have defined a method in a module and using it in another file.

Now let’s look into if __name__ == ‘__main__’:

Open the ‘’ file and edit it as given in following:


Leave ‘’ unchanged.

Now on your terminal run ‘’. 


Here we have imported the module mymath. The variable __name__ is set to the name of the module that is imported.

Now on terminal run ‘’


We have run the file as program itself. And you can see here the variable __name__ is set to the string “__main__”.
And we have checked if __name__ == “__main__” is True execute the following instructions which means if the file is run as standalone program itself execute the following instructions.

If you do  print(type(__name__)) in the program, you will see it returns ‘str’ (string) type.

Happy Coding!

Run commands on Fedora Atomic host from Remote host using Ansible

This post will show how to run commands on your atomic host from remote.

I am using Fedora Atomic host. Boot up your atomic instance. Make your you have Ansible installed on your control host.

The user of fedora instance is “fedora” by default and there is no password authentication. So first we will need to create password on the atomic for user “fedora”.

For that type the following command. It will ask for new password.

$ passwd

Now we will need to change PasswordAuthentication to YES . Open /etc/ssh/sshd_config on atomic host and change PasswordAuthentication to YES. Now The atomic host is all set :).

Go to your Remote host/Control host. I am using Fedora Workstation.

Now we need to generate ssh key on our control host.

Type the following command. This will create ssh key(private and public) on your host. The default location is of public key is ~/.ssh/

$ ssh-keygen

It is time to add the ssh key to the Atomic host.
Type the following command. This will add your ssh public key to .ssh/authorized_keys on atomic host.

$ ssh-copy-id username@IPofAtomicHost

Now we will create inventory and config file for Ansible.

$ mkdir test && cd test
$ touch inventory
$ touch ansible.cfg

Inside the inventory file add the following:


Inside the ansible.cfg file add the following:


Now let’s ping the atomic host :).

$ ansible atomic -i inventory -m ping

If the above returns Success we will try to run command on atomic host from our remote host :).
Type the following to run command on your atomic host.

$ ansible atomic -i inventory -m command -a "sudo atomic host upgrade"


NOTE: If you have you atomic instance running on Openstack make sure to add icmp to the security groups of the instance.



Run Apache on Fedora Atomic Host

This post describes how to run Apache on Atomic host. I am using Fedora atomic host.

Boot up an atomic instance (Fedora preferred).

To test the Apache container, just run

atomic run

Make sure you are using


After the container has started successfully, Now do

curl http://localhost:80

This will display


Now If you want to build your own image copy the source down to your host. 

Then Edit the Dockerfile and make your changes.

Now Build the image:

# docker build --rm -t /httpd .

After the build is successful, Run the container:

# docker run -d -p 80:80 /httpd #To assign port 80 of your host that maps to port 80 on the container
# docker run -d -p 80 /httpd #To assign random port that maps to port 80 on the container

If you do curl http://localhost you will see the required output.

Screenshot from 2016-09-06 10-55-07

Screenshot from 2016-09-06 10-58-21

IRC Client: Irssi On Atomic Host

If you are a terminal geek you will always want to do things using terminal ;). And when it comes to Atomic host, YES you will have to do stuffs using terminal.

If you don’t know about Atomic, you must visit 🙂

This post will describe how to setup and use IRC client on Atomic host. This will be applicable for any Cloud host also.

Irssi is a terminal based IRC client for Unix/Linux systems. And the best part is we will not need to setup things manually because we have containers :).

Let’s Get Stared:

I am using Fedora Atomic host here. Get Fedora atomic host from here

Make Sure you have Docker installed.

Copy the Dockerfile from here:

Now run docker build -t username/irssi .This will build image.

There after you just need to run the container 🙂  docker run -it username/irssi.

Later on sometime you will be able to do the whole set up only docker run -it fedora/irssi once Fedora adds Irssi to its Docker hub :).

After you start the container you will see something like this:

Screenshot from 2016-08-19 14-12-05

Let’s join a channel

Screenshot from 2016-08-19 14-14-16

You will find the Irssi Commands here: Irssi Commands.