One of the easiest ways to move an existing Drupal site to Pantheon is to import a Drush archive file using our Terminus command-line interface. This automates the packaging of the existing installation, improving the chances of success.
There are a few things you'll need in order to make this work:
The first thing you'll need to do is to generate a Drush archive of your existing site. If you have Drush access to the site direct via the shell, it's easy with the archive-dump command:
drush archive-dump --destination=drush-archive.tar.gz
Executed from the site root will create a file called drush-archive.tar.gz that's available via the public internet. If you have the file locally, you can put it on Dropbox, S3, or any number of other places. The important thing is that you have a Drush archive that can be downloaded via a URL.
If you haven't already, set up Terminus, the Pantheon CLI, using Composer as described in the installation instructions on GitHub.
Importing a Drush site archive as we've prepared it above is easy.
Authenticate into Pantheon with Terminus:
terminus auth:login --email=<email> --machine-token=<machine_token>
You're now ready to perform command-line operations with Pantheon! For instance, you can run
terminus site:list to get a list of your existing sites.
Start an import:
terminus site:import <site> <url>
At that point the script will poll as the site containers are spun up and the archive is imported. You can wait for that to complete, or cancel out and check back in your Dashboard.
Every aspect of the Terminus process is designed to support automation. You can script out imports like this to run several concurrently (or in serial).
Terminus is a rapidly evolving project, so stay tuned. Let us know what you would like to see, and forks and pull requests are always welcome!