I recently needed to re-save all the nodes of a particular content type (after I had added some fields and default configuration) as part of a Drupal 8 site update and deployment. I could go in after deploying the new code and configuration, and manually re-save all content using the built-in bulk operation available on the /admin/content page, but that would not be ideal, because there would be a period of time where the content isn't updated on the live site—plus, manual processes are fragile and prone to failure, so I avoid them at all costs.

In my Drupal 8 module, called custom, I added the following update hook, inside custom.install: