Shifter now supports a dedicated CDN service for media, and it's called Shifter Media CDN.
We want to introduce how to migrate your media on the external server or storage to Shifter Media CDN on Shifter Static.
How to migrate to Shifter CDN from external CDN
Step 1. Stop WordPress on Shifter dashboard if you're running.
Step 2. Make sure Media CDN is disabled on Shifter dashboard.
For more details, read Shifter Media CDN article
Step 3. Download media to your local machine.
You can media through SFTP/SSH from your media server.
If your media is on AWS S3, you can download it with AWS Command Line Interface (aws-cli), for example:
aws s3 cp s3://my-offload-media/wp-content/uploads --recursive ~/backup/
Step 4. Start WordPress then upload media to upload directory with File Manager plugin.
Note: Keep Media CDN disabled.
Step 5. Stop WordPress and enable Media CDN.
For more details, read Shifter Media CDN article
Step 6. Start WordPress and transfer uploaded media to Shifter CDN.
This backend process may take a while, keep the WordPress dashboard up until all thumbnails appear on the media library page.
Step 7. Rewrite path to the media on your posts with the plugin
Step 8. Regenerate media's thumbnails with regenerating thumbnail plugins after transfer completed.
That's all.