Unmounting a drive on macOS ensures that data is not being read or written when you physically disconnect the drive.
Why should you unmount a drive in macOS
Unmounting a drive in macOS (or any operating system) before physically disconnecting it is crucial for several reasons:
- Data Integrity: If any data is being written to the drive when you physically disconnect it, you might interrupt the process. This can result in partial files, corrupted data, or a corrupted file system.
- Data Loss Prevention: Some files may be cached (temporarily stored in your computer’s RAM for quicker access) and not immediately written to the external drive. Unmounting ensures that all cached data is safely written to the drive before it’s disconnected.
- OS Stability: Abruptly removing a drive without unmounting can sometimes cause system errors or software crashes. Unmounting alerts the system that the drive will be disconnected, so it can safely close any processes or references associated with that drive.
- Drive Health: Repeatedly disconnecting a drive without unmounting can wear out the drive’s electronics faster, especially if it’s interrupted during a write or read operation.
- Feedback: When you try to unmount a drive, the OS can warn you if there are applications or processes still using it. This allows you to close those applications or save your work before proceeding.
- Standard Practice: Beyond the technical reasons, it’s a best practice taught to ensure that all processes involving the drive are completed and to cultivate a habit of safe handling of devices and data.
How you can unmount a drive in macOS
- Open Finder.
- In the Finder sidebar, look under the “Devices” or “Locations” section (depending on your macOS version).
- Locate the drive you want to unmount.
- Click the eject icon (a triangle over a horizontal line) next to the drive’s name.
Using Disk Utility:
- Press Command + Space, type “Disk Utility”, and hit Enter to open Disk Utility.
- In the left panel, select the drive or volume you want to unmount.
- Click the Unmount button located at the top of the window. (Note: In some macOS versions, this may be labeled as “Eject”.)
- Open Terminal (you can use Spotlight with Command + Space and type “Terminal”).
- Enter diskutil list to see a list of all drives and their identifiers.
- Find the identifier for the drive or volume you want to unmount (e.g., disk2s1).
- Type diskutil unmount /dev/disk#s# replacing #s# with the identifier of the drive or volume.
- Press Enter.
After you’ve unmounted the drive, it’s safe to physically disconnect it from your Mac. If you’re going to work on the drive using command-line tools or other utilities, unmounting it first ensures data integrity.