How to be sure a drive has ejected from a Mac

macOS has several ways to properly eject a storage device.

Mac hard drive icon
Credit: Apple

Bob Cronan wonders how to be sure that macOS is no longer using the USB stick he relies on before he physically removes it from his Mac.

How do I know that the ‘stick’ is completely released/powered-off before I remove it? If I recall correctly, other OSes issue a message that it’s safe to remove the volume.

This is one of the most-asked questions we receive, and while we’ve answered aspects of it in recent years, Mac 911 hasn’t offered all the details in one place.

Apple has gotten much better about letting you know the status of a mounted disk or networked volume over the history of OS X and now macOS. It used to be maddening to know what was going on. Later, you received an error, but had no action to take. In the current form of the last few releases, the OS gives you a variety of feedback.

You can eject a physically attached, inserted, or networked volume by:

  • Right-clicking it and selecting Eject “Volume Name”.
  • Selecting it in any view (on the Desktop, in a Finder window, etc.) and choosing File > Eject “Volume Name”.
  • Dragging it on top of what looks like the Trash icon in the Dock, but which changes to an eject symbol when you start dragging.
  • Bringing up any Finder window, and clicking the Eject icon next to the drive’s name in the sidebar. (If you don’t see the sidebar, choose View > Show Sidebar. If drives don’t appear below the Devices label, choose Finder > Preferences > Sidebar, and make sure the appropriate options are checked in the Devices section.)

Once you’ve initiated eject, OS X and macOS fade the device’s icon while the process of removing temporary files and confirming no application or background process has files on the drive that are in use. If all goes well, the drive then disappears from the Desktop and sidebar. Sometimes the grayed-out stage happens so quickly that you don’t even notice it.

If anything running on your Mac still has active and open files, the OS used to just tell you that the drive was in use and left you to your own, er, devices. But the improvement in modern versions is that, after a moment, you’re told either which application has prevented ejection or that one or more applications is making use of it.

At this point, you should see a spinner labeled Trying To Eject while the OS waits to see if file usage changes, which could happen if you quit a program and immediately tried to eject. Failing that or after that attempt has timed out, you should have a dialog with the buttons Try Again, Cancel, and Force Eject. Try Again is useful if you’re still waiting for a program to quit, while Cancel is obvious.

Force Eject is a dangerous choice, because it can render some files on the ejected drive unreadable or in a weird state. It should be a very last resort.

I provided one deeper technical option to track down applications that won’t let go in this column from last year, which requires using the Terminal app and the command line.

You can also check the system log, a low-level text file that tracks certain activities (often failures):

  1. Launch Applications > Utilities > Console.
  2. Click the system.log link in the left sidebar.
  3. Click in the text at right and press Command-F (or choose Edit > Find > Find), and then UnmountAssistantAgent

If anything matches, you’ll see the name of a program or system tool. For instance, items that start with mds have to do with Spotlight indexing.

If all else fails, shutting down the system lets you remove anything attached that the system won’t let go with the least chance of file corruption.

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