Drush is a requirement on the host?

[mjordan]

Drush 9.0+ is in the "Requirements" list. This is on the host where you're running docker-compose?

[dannylamb]

Drush, Composer, PHP and all its extensions, etc... aren't needed for the demo environment. But if you're doing local, then you'll want it b/c you're managing the codebase on the host. You drush cr and composer require on something locally and it gets reflected in the container.

[noahwsmith]

I've been running it inside the containers e.g. docker-compose exec drupal with-contenv bash -lc 'drush updb'

But you could run it on your local if you have it installed there.

[dannylamb]

I personally had to install composer and then a handful of PHP extensions (mbstring, pdo_mysql, and gd are the ones I remember of the top of my head), but once done I could just use the copy of drush in the codebase folder. Specifically, if I'm in codebase, I run vendor/bin/drush cr.