I already have images on my disk and I don’t want to exhaust the network bandwidth of the cloud service (its getting too costly now)
How can I migrate to S3 (digital ocean S3 spaces) upload existing images and also use the image source as s3 link? I can make images public.
There are two parts to what you are trying to do.
Follow any tutorial out there for how to upload a folder full of images to S3 and host them as a public website.
The base URL of the images is expected to change. So use a tool like gctools find-replace to find and replace all mentions of the old base URL with the new base URL.
For that, use the Ghost S3 Storage adapter. Docs are here: Official Ghost + Amazon S3 Integration
You’ll also find there some examples of how to migrate photos to S3 if they are stored on Google Drive or Dropbox.