Django on RHEL9

The reason I am revisiting my Django website is because I am updating the operating system to RHEL9. At the same time I decided to take the opportunity to correct a couple of things I was unhappy with in the previous setup.

I prefer to take a clean VM and build from that. That way we know the exact configuration and can document it.

Set up Linux

We need to install the following (Using YUM)

python3
python3-devel
httpd (i.e. Apache)
postgresql

And the following are installed with pip

Django
social-auth-app-django

Create the database.

Postgresql has instructions for installing on RedHat. However my administrator has already installed postgres for me, so I just used that installation. The difference is that the service is called postgresql without a version number.

Set up the database

Make sure the database accepts passwords. The documentation suggests we should be using sha-256 rather than md5 for passwords, so we can configure them as follows:

Edit /var/lib/pgsql/data/postgresql.conf and ensure the password encryption is scram-sha-256:

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password_encryption = scram-sha-256              # md5 or scram-sha-256

Edit /var/lib/pgsql/data/pg_hba.conf and change the following lines:

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host    all             all             127.0.0.1/32            ident
host    all             all             ::1/128                 ident

To:

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host    all             all             127.0.0.1/32            scram-sha-256
host    all             all             ::1/128                 scram-sha-256

Reload the service:

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systemctl restart postgresql

Export and Import the Data

Since this is a pre-existing website, I chose to export and import the data. This is a tiny database, so exporting in SQL format is fine.

On the old server I ran:

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su - postgres
pg_dump mydb > /tmp/my_db.sql

And on the new server I copied the file across, then ran the SQL into the database:

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# Switch to postgres user
su - postgres
# Run postgres sql interface
psql
-- Create the mydb database and user
create database mydb;
CREATE USER myuser WITH PASSWORD 'password';
-- exit and switch to the new user
\q
psql -U myuser -d mydb -W -h localhost
-- Run the backup file
\i my_db.sql
exit

Set up Django

Create the Project User and Set Up Python

We need to create a new user. It’s home directory will contain the django files, so it will be under /srv. As root:

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useradd appuser -G apache -d /srv/my_app --shell /bin/false
su - appuser --shell=/bin/bash
cd /srv/my_app
python3 -m venv myapp_env
. myapp_env/bin/activate
pip install --upgrade pip psycopg2

Having created the user we switch to it. We have to specify the shell as it’s default shell is /bin/false. Then we create the python environment, activate it and start to install some dependencies.

I packaged up my app, and added requirements as follows in setup.cfg.

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install_requires =
    Django >= 2.2.3
    djangorestframework >= 3.10.2
    Markdown >= 3.1.1
    social-auth-app-django

So I could install it as follows:

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pip install my_app.tar.gz

I then created the Django environment as before:

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mkdir my_app
cd my_app
django-admin startproject my_app

After this it is pretty much the same configuration as before, editing the urls.py, installed apps, DEFAULT_AUTHENTICATION_CLASSES, the database and others in settings.py

Run required utilities

Run the migrations:

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python3 manage.py migrate

Build the static files directory:

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python3 manage.py collectstatic

163 static files copied to '/var/local/www/django/static'.

I check here if the environment works.

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python3 manage.py runserver 0.0.0.0:8000

This isn’t suitable for production use though, I need to set up Apache.

Set up the Django Application Users

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# python3 manage.py createsuperuser
Username (leave blank to use 'root'): me
Email address: me@cam.ac.uk
Password: 
Password (again): 
Superuser created successfully.

Now I can log in to my Django website, and with this username I can create any other users I require.

I am using token authentication for the API, so I need to create a token for the user.

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python3 manage.py drf_create_token username

The token is echoed out to the terminal. This can be copied to the configuration of the API consumer.

Set up Apache

The Digital Ocean documentation is really useful here as is the official Django documentation.

WSGI

Apache uses WSGI to run Python processes. It seems that there is a Python 2 version already installed in the operating system. I couldn’t work out where it was from, but in any case the new one needed to be configured as follows:

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mod_wsgi-express install-module> /etc/httpd/conf.modules.d/02-wsgi.conf

The configuration for the old version was removed as follows:

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rm /etc/httpd/conf.modules.d/10-wsgi.conf

Apache Configuration

An Apache configuration for Django was created by creating /etc/httpd/conf.d/django.conf with the following contents:

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Alias /static /var/local/www/django/static
<Directory  /var/local/www/django/static>
  Require all granted
</Directory>

<Directory /var/local/www/django/myapp/>
  Require all granted
</Directory>

<Directory /var/local/www/django/myapp/myapp>
  <Files wsgi.py>
    Require all granted
  </Files>
</Directory>

WSGIDaemonProcess myapp python-path=/var/local/www/django/myapp:/usr/local/lib64/python3.6/site-packages
WSGIProcessGroup myapp
WSGIScriptAlias / /var/local/www/django/myapp/myapp/wsgi.py
WSGIPassAuthorization On

The static directory is the one that was built earlier using collectstatic.

Note that I haven’t used a virtual environment. Doing so seems quite straightforward, so this might have been a better thing to do. As things stand I had to add the location where Django and the rest framework were installed to the python-path. Should Python be upgraded this will need to change.

A quick test shows this runs on Apache.

Using a self signed certificate.

This VM is inside a NATted network. Nothing on the internet can see us, so we can’t get a Let’s Encrypt certificate. To make sure passwords to login to the admin site aren’t sent in the clear over the network, I will use a self-signed certificate.

There was already a self signed certificate, so just pointing the browser at the website using https worked. I had to accept the warnings that the certificate authority was untrusted. Also the certificate had expired. My understanding is that this means the traffic is encrypted over the network, but we can’t use the certificate to protect from man in the middle attacks, i.e. it won’t verify the server the request comes from. Since this is an internal network I think I am happy with this.

Prevent unencrypted traffic

This requires mod_rewrite which was already installed. I just had to add the following file: /etc/httpd/conf.d/http.conf

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<VirtualHost *:80>
ServerName fully.qualified.domain.name
Redirect permanent / https://fully.qualified.domain.name/
</VirtualHost>

Conclusion

This turned out to be a lot of effort, but now I have an application hosted that uses JSON REST APIs. This can be used by various scripts to keep information about the environments I maintain up to date.

Django on RedHat 9

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