Simple Drupal 6/7 to Drupal 8 Migrations

Christopher Bloom (illepic)

Scenario:

Legacy Drupal 6 site needs a migration to new Drupal 8 site. We want to migrate settings, content types, fields, users, files, content. The Drupal 6 site database is accessible from the freshly installed Drupal 8 database.

Caveats & Considerations

Not "in-place" upgrade like Drupal 6 to 7
No UI, command line only
Lots of contrib
Migrations changed from config to "plugins" in Drupal 8.1. If you're starting fresh in 8.1, no worries.
We can migrate configuration as well as content in Drupal 8

Modules + Tools Required

A Migration Group is a collection of Migrations
A Migration is generally one YAML file.
A Migration contains
- a source plugin: "read rows from source (D6)"
- a processing pipeline: "transform raw source values into what the destination needs"
- a destination plugin: "D8 understands what this thing becomes (nodes, users, entities)"
Processing plugins are simple PHP files to help massage data from source to destination

Looks like this all together as a module

A single Migration YAML file might look like this:

status: true
dependencies: {  }
id: upgrade_d6_node_page
migration_tags:
  - 'Drupal 6'
migration_group: migrate_drupal_6
label: 'Nodes (page)'
source:
  plugin: d6_node
  node_type: page
process:
  nid: nid
  vid: vid
  type:
    plugin: default_value
    default_value: post
  langcode:
    plugin: default_value
    source: language
    default_value: und
  title: title
  uid: node_uid
  status: status
  created: created
  changed: changed
  promote: promote
  sticky: sticky
  body/format:
    plugin: default_value
    default_value: basic_html
  body/value:
    plugin: remove_strings
    source: body

  field_media_primary:
    -
      source: nid
      plugin: img_assist
      type: 'mid'
    -
      plugin: iterator
      process:
        target_id: fid

  field_attachments:
    -
      plugin: iterator
      process:
        target_id: fid
        display:
          plugin: default_value
          default_value: 1
  field_group:
    source: nid
    plugin: og_lookup
destination:
  plugin: 'entity:node'
migration_dependencies:
  required:
    - upgrade_d6_user
    - upgrade_d6_node_type
    - upgrade_d6_file_media
  optional: { }

Tell D8 About Your D6 Database

In Drupal 8 settings.php, right next to your regular database configuration, add a db config FOR THE D6 SITE:

$databases['migrate']['default'] = array (
  'database' => 'dbname',
  'username' => 'dbuser',
  'password' => 'dbpass',
  'prefix' => '',
  'host' => 'localhost',
  'port' => '3306',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
);

You now have configuration for

$databases['my_d8_site']['default']
and $databases['migrate']['default']

This EXACT name for the D6 db config is extremely important:

$databases['migrate']['default']

Aight, D8. Generate a Migration

From the D8 site root, run:

drush migrate-upgrade --configure-only

Boom. D8 just took its best guess at figuring out all the fields, nodes, files, etc. (hopefully)

Now let's dump all this out as YAML files:

drush config-export --destination=/tmp/migrate

Many YAML files will now appear in /tmp/migrate. We're going to move all these to a custom module shortly.

Let's make a module so Drupal understands how to find this config

Use Drupal Console to generate a module for us

drupal generate:module

A series of questions will appear. We'll call the module custom_migration. Use the default options provided except:

Would you like to add module dependencies: yes

Module dependencies separated by commas:

migrate_drupal, migrate_plus

Create a folder in your new module:

custom_migration/config/install

Move our previously generated YAML to the new module:

cp /tmp/migrate/migrate_plus.migration.* \
    /tmp/migrate/migrate_plus.migration_group.migrate_*.yml \
    /path/to/your/module/config/install/

Just make sure you do NOT include the default config group file called migrate_plus.migration_group.default.yml

Let's run it

Running drush migrate-status shows us the individual migrations D8 knows about

$ drush migrate-status
 Group: migrate_drupal_6              Status  Total  Imported  Unprocessed  Last imported       
 upgrade_d6_system_site               Idle    1      1         0             
 upgrade_d6_url_alias                 Idle    6972   0         6972                             
 upgrade_d6_file                      Idle    9914   3499      0             
 upgrade_d6_user_picture_file         Idle    281    281       0             
 upgrade_user_picture_entity_display  Idle    1      1         0             
 upgrade_d6_user                      Idle    1402   1133      0             
 upgrade_d6_file_media                Idle    9914   3495      0             
 upgrade_d6_book_blog                 Idle    822    0         822                              
 upgrade_d6_node_event                Idle    1351   0         1351                             
 upgrade_d6_node_forum                Idle    2305   0         2305                             
 upgrade_d6_node_guild_app            Idle    679    677       0             
 upgrade_d6_node_image                Idle    2243   0         2243                             
 upgrade_d6_node_page                 Idle    9      0         9

Run all migrations:

drush migrate-import --all

Congrats!

Next up:

Modify incoming data with built-in process plugins:

source:
  plugin: d6_file
process:
  fid: fid
  # Skip any filename in the map below
  filename:
    -
      plugin: static_map
      source: filename
      bypass: true
      map:
        'gallery grid': ''
        preview: ''
        thumbnail: ''
        img_assist_properties: ''
        large: ''
    -
      plugin: skip_contains
      skip:
        - 'furiousraid'
    -
      plugin: skip_on_empty
      method: row
    -
      plugin: callback
      callable: basename
      source: filepath

Next up: Write your own process plugins
(in custom_migration/src/Plugin/migrate/process/ImagePath.php)

<?php

/**
 * @file
 * Contains \Drupal\df_migration\Plugin\migrate\process\ImagePath.
 */

namespace Drupal\df_migration\Plugin\migrate\process;

use Drupal\migrate\Annotation\MigrateProcessPlugin;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\Row;

/**
 * This plugin fixes d6 Image file names to be the actual filename from filesystem
 *
 * @MigrateProcessPlugin(
 *   id = "image_path"
 * )
 */
class ImagePath extends ProcessPluginBase {

  /**
   * {@inheritdoc}
   */
  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, 
                            $destination_property) {
    return basename($value);
  }
}

Next up: Edit a migration YAML file, reload it in Drupal, and rerun a migration

# Rollback migration
drush mr upgrade_d6_node_page

# (Edit the migrate_plus.migration.upgrade_d6_node_page.yml file)

# Now, hard reload the file using Config Development module
drush cdi1 modules/custom/df_migration/config/install/migrate_plus.migration.upgrade_d6_node_page.yml \
    && drupal cr all

# Re-run this migration
drush mi upgrade_d6_node_guild_app

Next up: unbork a crashed migration

drush php-eval 'var_dump(Drupal::keyValue("migrate_status")->set('your_migration_name', 0))'

Super Helpful Resources

Drupalize.me: Custom Drupal-to-Drupal Migrations with Migrate Tools
ChapterThree: Drupal to Drupal 8 via Migrate API
Sitepoint: Your First Drupal 8 Migration
DrupalEasy: Drupal 6 to Drupal 8(.1.x) Custom Content Migration

Drupal 8 Migrations

By Christopher Bloom

Drupal 8 Migrations

3,921

Christopher Bloom

Frontend developer, lover of design systems, CSS architecture, and all things javascript.

Simple Drupal 6/7 to Drupal 8 Migrations

Caveats & Considerations

Modules + Tools Required

Looks like this all together as a module

Tell D8 About Your D6 Database

Super Helpful Resources

Drupal 8 Migrations

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