How do I delete the data from my external hard drive that is now full and cannot complete any more backups from my iMac with Time Machine? I want to delete then complete a full time machine backup on the external drive.
Erase and re-format the external drive
as per > https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac
Note: erasing and re-formatting will completely wipe everything from the drive, including other none Time Machine data.
+1 Erase and reformat, otherwise buy a higher capacity EHD and move the content on the old drive to the new drive per How to Migrate a Time Machine Backup to Another Drive (howtogeek.com)
Time Machine unable to Backup to full external hard drive.
