Custom Content Type with Custom Fields creation I followed the examples given at: https://www.drupal.org/node/2629550  to create a new content type.  No problems there, the content type exists after I install the module.  However, when I uninstall, and re-install with the custom field yml files it says to have, I get errors saying that the field storage doesn't exists.   So I dug into core/modules/node/config/installand copied the field.storage.body and modified it for the field I wanted (username).  The field created, however, when I install the module now... It says:

Drupal\Core\Field\FieldException: Attempt to create a configurable field for a non-configurable field storage. in Drupal\field\Entity\FieldConfig-&gt;__construct() (line 94 of C:\xampp\htdocs\drupal-8.4.4\drupal-8.4.4\core\modules\field\src\Entity\FieldConfig.php).

Here is the yml for the custom content type: 

#node.type.faculty_bio.yml
langcode: en
status: true
name: "Faculty Bio"
type: faculty_bio
description: "Faculty Bio"
help: ''
display_submitted: true


and the code for the custom field:

#field.field.node.faculty_bio.username.yml
langcode: en
status: true
dependencies:
  config:
    - field.storage.node.body
    - node.type.faculty_bio
  module:
    - text
    - node
id: node.faculty_bio.username
field_name: field.storage.node.username
field_storage: username
entity_type: node
bundle: faculty_bio
label: Username
description: 'The username'
required: true
translatable: true
default_value: {}
default_value_callback: ''
settings:
  display_summary: true
field_type: text
I created the content type in a test environment, and populated all of the fields I wanted using the UI.  Then I went to the site configuration and did an export on the entire site. I pulled all of the yml files I needed for the fields and node types, and it works beautifully.