How do I give myself full read/write/admin access to Backups.backupdb on a old Time Machine HD
Time Machine is very much an &quot;all or nothing&quot; black box, with very little customization or control.
Files inside one dated backup folder may actually just be duplicate catalogue entries to the same data as the same 'file' in another dated backup folder. That's why unchanged files don't take up more space each backup, and why TM folders are a huge mass of interconnected trouble.
Deleting files from one snapshot probably won't save you any space at all, until you've deleted them from all of the snapshots, so that all catalog entries to the file data are removed.
Normally, the way to delete files or folders from the entire backup is to do so from within the TM application itself. Right-click on the files, and select the option to delete.
My advice is to copy one snapshot of the files that you want to keep to another disk, and then delete the whole backup (or erase the disk).
Oh, and don't forget to re-enable SIP! ;-)