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Rebuilding a Theme, Part II: Creating a Subtheme

Install and Enable the Theme

There are several options for developing with Boostrap for Drupal. I have used Radix before, and I liked it, but this time I want to use the Bootstrap5 theme because it isn't so heavily dependent on nodeJS.


  1. Install the Bootstrap5 theme: composer require 'drupal/bootstrap5:^4.0'
  2. Enable the Bootstrap5 theme: drush then bootstrap5

The README file included in the theme also suggests installing the companion module Bootstrap 5 tools, but it doesn't have a stable release, and it hasn't been updated since 2022, so I'm not going to do that.

Create a Subtheme

A subtheme allows developers to customize the theme without having all of their changes obliterated every time the theme is updated. The README provide a drush command: drush --include="web/themes/contrib/bootstrap5/src/Drush" bootstrap5:generate-subtheme MACHINE_NAME --subtheme-name="SUBTHEME_NAME". Obviously, replace MACHINE_NAME with the machine name for the subtheme (I'm using dll_catalog) and SUBTHEME_NAME with a human-readable name (e.g., "DLL Catalog Theme").

If all goes well, there should now be a directory called custom inside of web/themes. There should also be a directory inside of custom with the machine name that was specified in the drush command.

Enable the Subtheme and Set it as the Default

  1. Enable the subtheme: drush then dll_catalog (or whatever the SUBTHEME_NAME is)
  2. Set the subtheme as the default: drush config-set system.theme default dll_catalog

Now, clear the cache (drush cr), go to your browser, and pull up your site. The new subtheme should be in control. Here's a screen shot of mine at this stage:

Screenshot of my bare subtheme

Already I like this implementation of Bootstrap better than what I've found in Radix. Out of the box, as it were, the Bootstrap5 subtheme takes care of some things that I would have to handle with templates and CSS in Radix. Namely:

  1. The content is centered in the browser window. It's not difficult to do that (see, for example,, but it's nice not to have to cope with it.
  2. The footer is already pushed to the bottom of the browser window. That, too, can be dealt with easily, but I'd rather move on to other things.

As much as I like those things, it's time to customize my subtheme.