My problem is that I have an external hard drive connected to my Mac. Since it is only used for backup purposes, it is sleeping most of the time.

However if I now want to save something (e.g. a picture from a website) to my internal hard disk, I have to wait for the external one to wake up before the "save as..." dialogue appears.

I know about the question How to save a file quickly and no need to wait for the external hard drives to "wake up"?, but it sounds like it intends a solution about not letting the hard disks go to sleep whereas I would like to let the external hard drive have its well-deserved rest.


  • I do not want to unplug it, because I know that I will forget to reconnect it before the automatic backup
  • various other operating systems deal very well with situations like that


Using Sherwood Botsford's answer I put together the following AppleScript which mounts the hard drive, executes for example an rsync and unmounts it again.

do shell script "diskutil mount 'Name of your Volumn'"

do shell script "rsync -av --delete ~/ '/Volumes/Name of your Volume/.'"

do shell script "diskutil unmountDisk 'Name of your Volume'"
  • 4
    I'm really looking for a real answer to this question, not just answers that revolve around "unplug the drive." When a save dialog opens, there should be zero reason to spin up any external drives, as long as the save location is not on one of those drives. This is bad behavior and Apple has known about it for years.
    – Guillochon
    Jan 29, 2014 at 0:24

1 Answer 1



A: Unmount the disk from the command line.

diskutil unmountDisk Lacie

would be the command to unmount a disk that has a file system named Lacie on it. You can also refer to the device itself, but devices can vary from one mount to another. unmountDisk will take any file system name as the object but will unmount all other file systems if the drive has more than one.

Then, when you want to do a backup,

 diskutil mount Lacie

You also need to disable spotlight from indexing this drive.

  • 1
    You could write a script that mounts the drive periodically to allow backups, but leaves it unmounted most of the time. If you scheduled the script via launchctl, that would achieve the "set it and forget it" behavior that samcarter wants. Feb 7, 2014 at 22:05
  • For all applicable volumes, would you like the option of discreet but distinctive Unmount icons (two arrows, seen in Disk Utility) in both (a) the sidebar of Finder and (b) Columns view at the Computer level? Feb 10, 2014 at 5:31

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