Ask Different is a question and answer site for power users of Apple hardware and software. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I recently installed an SSD and made it my boot disk, and installed a 1TB HDD on a Caddy, where the DVD-ROM used to be. The one drawback is that having a second drive actually lowers the battery life quite a bit, so hence my question:

I know I can unmount the drive (eject it) so that it doesn't spin when needed, but, is there a way to re-mount it without having to reboot the Mac? I don't mind if it's a terminal command.

Thanks in advance :)

share|improve this question

I'm assuming that you're talking about ejecting the drive using the the Finder. If so, then simply unmounting the disk, as opposed to ejecting it, should allow it to remain in the list of attached disks so that you can re-mount it later. For example, using

diskutil unmountDisk <device or name>

in the Terminal can be used to unmount the disk, but still leave it in the available drives list which can be seen by using

diskutil list

which can also be used to discover the <device or name> you require. Then to re-mount the disk you can use

diskutil mountDisk <device or name>

Note that all the above can also be done using the built-in Disk Utility application, just use the Mount/Unmount button as opposed to Eject.

share|improve this answer
Huh, interesting, and do you know if this would keep the disk from spinning up? (since it's unmounted and not ejected) – Ian Sep 1 '12 at 16:33
I tried unmounting it, but the disk keeps spinning, which is not what I want :( Is there a way to eject it and "uneject" it? – Ian Sep 1 '12 at 16:37
@Ian Not easily, AFAIK. Take a look at the comments and answer to re-mount ejected SD card without reinserting to see if it helps – binarybob Sep 1 '12 at 16:40
Sounds too invasive to reload kernel extensions hehe, I'll just have to accept that the battery lasts a little less. Thank you ;) – Ian Sep 2 '12 at 16:40

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.