How to build a OCI Compliant image using buildah
Here in this article we will try to build a custom image using buildah to host a Django Web Application.
Test Environment
Fedora 32 installed
What is Buildah
Buildah is a opensource tool developed to build container images which are compliant with Open Container initiative (ie. OCI) image specifications. In this article we will see how we can install buildah tool. Also, we will see how it can be used to build container images.
Image can be built from existing images, from scratch and using Dockerfiles. Buildah is currently supported only for Linux distributions and it does not support Windows or Mac OS platforms at this time.
If you are interested in watching video. Here in the YouTube video on the same step by step procedure outlined below.
Procedure
Step1: Installing Buildah on Fedora Linux
In order to Build OCI compliant Linux containers we first need to install the Buildah utility on our Linxu OS. Installing Buildah is as simple as shown below without the overhead of installing the client and server packages like we do for setting up Docker.
[admin@fed32 ~]$ sudo dnf -y install buildah
Step2: Download the Fedora base image
As a first step, we will try retrieve the fedora base image using the below command. We will use this fedora base image as the initial layer on top of which we will install the required software’s to host or deploy our Django application.
[root@fed32 ~]# buildah from fedora
Getting image source signatures
Copying blob 22cef3226003 done
Copying config e6b57c0d9f done
Writing manifest to image destination
Storing signatures
fedora-working-container
Once we download the fedora base image using buildah it will actually download an image and along with that a working container is also created as shown below.
[root@fed32 ~]# buildah images
REPOSITORY TAG IMAGE ID CREATED SIZE
registry.fedoraproject.org/fedora latest e6b57c0d9f53 5 days ago 208 MB
[root@fed32 ~]# buildah containers
CONTAINER ID BUILDER IMAGE ID IMAGE NAME CONTAINER NAME
f970f6155e37 * e6b57c0d9f53 registry.fedoraproject.org/fe... fedora-working-container
[root@fed32 ~]# buildah run fedora-working-container /bin/bash
[root@f970f6155e37 /]# cat /etc/redhat-release
Fedora release 32 (Thirty Two)
Step3: Install Python 3.8 and pip on the Fedora base image
Once the base image is downloaded, let try to install Python 3.8 along with pip package as shown below using the buildah run command.
Install Python 3.8 in container
[root@fed32 ~]# buildah run fedora-working-container -- dnf -y install python3.8
Fedora 32 openh264 (From Cisco) - x86_64 1.0 kB/s | 2.5 kB 00:02
Fedora Modular 32 - x86_64 228 kB/s | 4.9 MB 00:22
Fedora Modular 32 - x86_64 - Updates 238 kB/s | 3.7 MB 00:15
Fedora 32 - x86_64 - Updates 324 kB/s | 26 MB 01:21
Fedora 32 - x86_64 622 kB/s | 70 MB 01:55
Package python3-3.8.5-5.fc32.x86_64 is already installed.
Dependencies resolved.
Nothing to do.
Complete!
Install and validate pip in container
[root@fed32 ~]# buildah run fedora-working-container -- dnf -y install pip
...
Installed:
libxcrypt-compat-4.4.17-1.fc32.x86_64 python3-pip-19.3.1-4.fc32.noarch python3-setuptools-41.6.0-2.fc32.noarch
Complete!
[root@f970f6155e37 /]# python3 --version
Python 3.8.5
[root@f970f6155e37 /]# pip --version
pip 19.3.1 from /usr/lib/python3.8/site-packages/pip (python 3.8)
Step4: Install Django
Now, we have the pre-requisite software (ie. Python and pip) installed, we can go ahead and install the Django pip package as shown below.
Install and validate Django in container
[root@fed32 ~]# buildah run fedora-working-container -- pip install Django
WARNING: Running pip install with root privileges is generally not a good idea. Try `pip install --user` instead.
Collecting Django
Downloading https://files.pythonhosted.org/packages/50/22/4c91847beceadbb54b5a518909ed5000bb1777168c7d6b087e8f79e5e05b/Django-3.1.2-py3-none-any.whl (7.8MB)
|████████████████████████████████| 7.8MB 347kB/s
Collecting sqlparse>=0.2.2
Downloading https://files.pythonhosted.org/packages/14/05/6e8eb62ca685b10e34051a80d7ea94b7137369d8c0be5c3b9d9b6e3f5dae/sqlparse-0.4.1-py3-none-any.whl (42kB)
|████████████████████████████████| 51kB 2.0MB/s
Collecting asgiref~=3.2.10
Downloading https://files.pythonhosted.org/packages/d5/eb/64725b25f991010307fd18a9e0c1f0e6dff2f03622fc4bcbcdb2244f60d6/asgiref-3.2.10-py3-none-any.whl
Collecting pytz
Downloading https://files.pythonhosted.org/packages/4f/a4/879454d49688e2fad93e59d7d4efda580b783c745fd2ec2a3adf87b0808d/pytz-2020.1-py2.py3-none-any.whl (510kB)
|████████████████████████████████| 512kB 2.6MB/s
Installing collected packages: sqlparse, asgiref, pytz, Django
Successfully installed Django-3.1.2 asgiref-3.2.10 pytz-2020.1 sqlparse-0.4.1
[root@fed32 ~]# buildah run fedora-working-container /bin/bash
[root@f970f6155e37 /]# pip list
Package Version
---------- -------
asgiref 3.2.10
Django 3.1.2
gpg 1.14.0
libcomps 0.1.15
pip 19.3.1
pytz 2020.1
rpm 4.15.1
setuptools 41.6.0
sqlparse 0.4.1
Step5: Create a project named mysite in folder /home/admin/Django_Projects
Right now we have our Python Django web framework libraries installed. We can try to build a Django project as shown below. First we will create a directory and then use django-admin tool to start a new project named mysite. Once the mysite project is built we will set this project folder directory as the working directory in our image.
Create Django project and set the working directory within container
[root@fed32 ~]# buildah run fedora-working-container -- mkdir -p /home/admin/Django_Projects
[root@fed32 ~]# buildah config --workingdir /home/admin/Django_Projects fedora-working-container
[root@fed32 ~]# buildah run fedora-working-container -- django-admin startproject mysite
[root@fed32 ~]# buildah config --workingdir /home/admin/Django_Projects/mysite fedora-working-container
Step6: Configure the command to run with the container
Now, that we can our default project setup ready, we need to set the PATH to point to the python executable as shown below and launch the django lightweight web server on port 8000 when the cmd step is executed.
[root@fed32 ~]# buildah config --env PATH=$PATH:/usr/bin/python3.8 f970f6155e37
[root@fed32 ~]# buildah config --cmd '"/usr/bin/python3.8" "manage.py" "runserver" "0:8000"' fedora-working-container
Step7: Expose the Port to access Django website URL
We need to expose the port 8000 of Django web server that will be used to access the default Django web application.
[root@fed32 ~]# buildah config --port 8000 fedora-working-container
Step8: Commit the changes to the container into a new image
Now, we have all the required software installed and configuration completed. We can commit all these changes to create an image named hellodjango using the buildah commit command.
[root@fed32 ~]# buildah commit fedora-working-container hellodjango
Getting image source signatures
Copying blob 4f51e20f4794 skipped: already exists
Copying blob 09c674fe9922 done
Copying config 05fa2ff411 done
Writing manifest to image destination
Storing signatures
05fa2ff411ad87061e9cc43dee851fef8e3525e8a7c3edb4fa988e676f27a120
Let’s try to list our the images currently available using podman tool once the above commit is completed. This will show our newly built Django web application image.
[root@fed32 ~]# podman images
REPOSITORY TAG IMAGE ID CREATED SIZE
localhost/hellodjango latest 05fa2ff411ad About a minute ago 699 MB
registry.fedoraproject.org/fedora latest e6b57c0d9f53 5 days ago 208 MB
Step9: Create a container for image hellodjango
Lets try to run a container from the image that has been committed in our previous step. We are using port forwarding to access the Django application hosted on port 8000 to be accessible from host machine on port 8000.
[root@fed32 ~]# podman run -dt -p 8000:8000 localhost/hellodjango
Step10: Validate the default Django application
Once the container has been instantiated, we can launch the url to get the default Django page.
URL: http://localhost:8000/
Hope you enjoyed reading this article. Thank you..
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