disk0s2 vs. disk1s2?

Discussion in 'macOS' started by lip5016, Dec 10, 2014.

  1. lip5016 macrumors regular

    Jul 11, 2014
    hello! I was just curious if anybody could tell me… in a MacBook Pro with 2 internal drives, one drive in the main hard drive bay, and another drive in the SuperDrive bay..

    is "disk0s1" typically the drive in the "main hard drive bay" and "disk1s2" typically the drive in the SuperDrive bay?

    thanks! :)
  2. SlCKB0Y macrumors 68040


    Feb 25, 2012
    Sydney, Australia
  3. lip5016 thread starter macrumors regular

    Jul 11, 2014
  4. chrfr macrumors 604

    Jul 11, 2009
    It's unsafe to make these assumptions. Verifying the disk and partition is the only safe way to do any sort of disk operations, although typically disk0 is the main disk.
    The "s1" and "s2" refer to partitions on the disks, which is why you need to look at your specific environment.
  5. AlecZ macrumors 65816


    Sep 11, 2014
    Berkeley, CA
    Yeah, you can't assume that disk0s2 is the main partition and that disk1s2 is the DVD drive. For me, disk1s2 is a mounted disk image partition.
  6. alex0002, Dec 26, 2014
    Last edited: Dec 26, 2014

    alex0002 macrumors 6502

    Jun 19, 2013
    New Zealand
    In a "normal" single disk installation, disk0 represents the whole disk, disk0s1 is the EFI system partition (user applications don't access this) and disk0s2 is the OS X partition containing both operating system and user data. The following example is from a Macbook Pro running OS X 10.9.5 with a single 240GB SSD.

    $ diskutil list
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *240.1 GB   disk0
       1:                        EFI EFI                     209.7 MB   disk0s1
       2:                  Apple_HFS MacSSD                  239.2 GB   disk0s2
       3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
    If you have a second disk, it probably doesn't have an EFI system partition, so the first user partition on that drive might be disk1s1.

    If you select About This Mac in the drop down menu from the Apple symbol, it should confirm the name of the startup disk (partition). Or use System Preferences -> Startup Disk.

    If the drives are physically different (SSD and HDD) and different sizes, then the output of the diskutil command should be enough to tell which is which. In my case about I know that the 240GB SSD is installed in the default internal hard disk location.

    Perhaps a copy and paste of your diskutil list output would help.

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