Does ejecting an external disk during a TM Backup result in a bad backup?

Just to add, you can stop a Time Machine backup, you can eject a Time Machine drive while it's backing up, you can restart or shutdown a Mac while Time Machine is backing up. In all those scenarios a Mac will close the backup safely. Just don't unplug it while backing up.

If you’re particularly concerned about this, get a NAS with Time Machine support and teach the users to shut down the Mac before they leave the Wi-Fi network with their equipment. This reduces the opportunities to yank cables.

With direct-attached storage, teach them to shut down before they disconnect cables.

Or disable automatic backups, and teach the folks to request a manual backup and to leave it running and leave it cabled until completion: Start, pause, or resume a Time Machine backup on Mac - Apple Support

Your fundamental issue is people, and there is no technical solution to a people problem. Yanking cables mid-backup or mid-anything-actively-transferring is bad.

I am not aware of any app which takes additional control of macOS and Time Machine.

Or disable backups entirely, as nobody here cares a whit about their data, and that’s not your issue. Nor is fixing the results.

If you should decide to continue in your current role here, welcome to IT. This is one of the ongoing sources of tension and conflict when IT is supporting users. Some users will routinely derail backups, but it’s IT’s problem to fix problems when data goes missing or dropped or dunked or corrupted.

I usually suggest shutdown, as it’s simpler. And it cleans up other messes, too. Various apps (and macOS itself, in some cases) have too often had resource leaks.

Yes, TM should clean up from a clean dismount, but TM should be stopped first, and then the dismount.

I haven’t met a TM corruption on a clean dismount or a clean shutdown.

I have met TM corruptions on yanked cables, and on power outages.

NAS beats DAS around forgetting, and around yanking, and around sharing a storage pool or two.

I don’t generally prefer AppleScript, as it too has too often fallen short of local needs and expectations.

You should see a backupd process active when TM is active, if you want to script this with AppleScript or zsh or bash or some Swift app. The app will need system access sufficient to spot the active backupd, obviously.

FWIW, you should never unplug an external drive without ejecting it first, Time Machine or not.

No idea what "Mountain" is.

Bryan Schmiedeler wrote:

My wife is not going to do this. Many people I help with Macs are not going to do this.

Would this be useful?

Most computer users know not to unplug a drive without ejecting it first, and not just Mac users. Not sure how having an app to eject all drives in the menu bar will guarantee someone will use it.

Bryan Schmiedeler wrote:

Just to confirm, if there is a Time Machine backup in progress and the user tries to eject the disk, the OS will safely stop the TM backup and then eject the disk?

Didn't believe me aye? 😎