External hard drive won't free up space after deleting files.

barneyhairball wrote:

Yes, I see what you mean by Enter Time Machine. But Control-click does not give the option of Delete all backups ...

I can think of only one valid reason to do that: one might, for example, wish to delete all existing copies of some sensitive information wherever they may reside. Deleting files from an encrypted source volume takes care of them, but backup copies will remain on backup device(s) until TM decides it requires more space. If you "delete all backups of <...>" it takes care of them, in addition to all earlier versions of that item.

It does take a lot of time. In such circumstances it generally makes more sense to simply erase the entire backup drive. Encrypted copies cannot be resurrected.

The short answer is that you will need to erase that TM backup drive, but before you do that back out of that first screenshot that shows the contents of "MacBook Air":

Next, open that Backups.backupdb folder. It should contain one and only one folder within it, bearing the name of the Mac it's backing up.

Since that screenshot only shows the contents of "MacBook Air" I cannot be certain it is the only folder within Backups.backupdb. If there is another folder within it, that would be the redundant one I speculated might be present. Collapse the "reveal triangle" adjacent to "MacBook Air" to determine if another backup of that Mac is present, under a different name.

If that's the case, you would need to erase the drive anyway because Time Machine "owns" that drive and everything in it.

It gets worse though, because if you manually erased backups using the Finder (which is not clear to me yet) it's very likely the TM database was rendered invalid and and unusable for purposes of restoring an entire system. At best it should be considered unreliable, and an unreliable backup is worse than none at all.

So, my recommendation is to obtain another TM backup drive, create a new backup with it, then erase the existing drive. Not only are external drives inexpensive, one and only one backup device isn't a robust backup strategy anyway. A 2 TB drive will cost only a few dollars more than a 1 TB drive. Time Machine will back up to both of them — or as many additional drives as you may want to give it — in a "rotation" fashion. If one backup drive isn't available, it skips to the next one, and so forth.

By the way get rid of any Western Digital's drive "manager" or "utility" software that they are fond of bundling with their products. They are not required, and using them has been known (in the distant past) to have corrupted perfectly good drives. I mention that only because there is a mounted "WD Apps" volume on that Mac. The first thing anyone should do with any external drive is to format it with Disk Utility. That accomplishes two objectives: it prepares the drive for use with your Mac, and it gets rid of the junk software that may be on it.

Sometimes, a change in your Mac's name or similar circumstance may result in a separate Time Machine backup that you are no longer using. You may or may not need to obtain a larger capacity backup drive, so before drawing that conclusion investigate the following.

Open the Time Machine backup drive in the Finder to examine its contents, but do not alter them. If that TM backup drive is dedicated exclusively for that Mac's backups, there should be one and only one item at its root level. It should be named Backups.backupdb. Is that what yours shows?

Next, open that Backups.backupdb folder. It should contain one and only one folder within it, bearing the name of the Mac it's backing up. Is that what yours shows?

Once again, do not alter any of that drive's contents. If you do that (or if you already altered its contents by erasing files or folders), then you should erase the TM backup drive completely.

I still recommend erasing that backup drive, after getting a replacement of course. The reason is that deleting backup folders in that manner using the Finder is supposed to work, but often results in corrupting the TM backup database.

The reason that happens is unclear to me, so I can only speculate it occurs because deleting folders using the Finder can take a long time. As in, hours. What may happen is people get impatient and unplug the drive, or shut down the Mac, etc. Even then it's not supposed to corrupt the database, but the practice I recommend is to delete backups only through the Time Machine interface: "Enter Time Machine", then control-click the backup file you want to delete, and select "Delete all backups of..." the file. That works reliably.

barneyhairball wrote:

I can open time machine preferences but there are no backup files to be seen; I cannot see the option "Delete all backups of..." the file.

You need to "Enter Time Machine" to do that. Control-click the backup file you want to delete, and select "Delete all backups of..." the file.

Once a TM backup has been altered by manual intervention using the Finder, it should no longer be considered reliable.

Time Machine works best when it's simply left alone. Turn it on and forget about it.

Besides erasing the TM backup drive, which is what I've been recommending all along? No.

I have become increasingly convinced that TM backup should no longer be considered reliable.