To whom it may concern:
When you deploy an app based on a Buildpack (such as a Ruby on Rails application, but also e.g. a NodeJS or Go application), you might be wondering how to run the tasks which one would normally manage using e.g.
heroku run taskname.
In our case, we were deploying a Rails application, and wanted to enter the Rails console.
/ap/bin/bundle exec rails console did not work, because the Ruby version which is installed globally in the container was Ruby 2.7.0, while the app was running on Ruby 2.6.6.
It turns out that the tasks you are looking for live in the
/cnb/process/ directory. (‘cnb’ stands for ‘Cloud Native Buildpacks’).
In our case,
/cnb/process/console would open up the Rails console.
It was impossible to find any information about this elsewhere and it was only by trial and error that we found out how it works. I hope that by writing this post some other people might be helped in the future if they are searching for the same thing .