I have multiple hard drives, each containing various partitions, with various bootable OS X versions on them.

This Apple support link, despite the title, Determine which disk started up your Mac, just tells me which hard disk is selected for a normal boot:

  1. On your Mac, choose Apple menu > System Preferences.

  2. Click Startup Disk.

    Your selected startup disk is shown at the top of the preferences pane.

However, if I booted whilst holding the Option key and selected a different disk, the Startup Disk control panel doesn't reflect which disk I actually booted from.

Disk Utility doesn't appear to explicitly show this information either, although it seems to imply that the active system disk is the pre-selected disk - upon opening the application.

How can I quickly determine which disk my Mac booted from (via the UI or command line)?


From the menu bar, select About this Mac, as shown below.

enter image description here

You should then get a popup window showing the startup disk, as shown below.

enter image description here

You can also get the startup disk by entering the command given below.

diskutil info / | grep "Volume Name"

Example output is given below.

   Volume Name:              Marlin

The version of macOS can be found in the by using the command below.


Example output is given below.

ProductName:    Mac OS X
ProductVersion: 10.13.6
BuildVersion:   17G14042


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