Goal: clone my internal disk to an external disk, and boot from the external disk.

update thanks klanomath, who pointed out that I had to change the uuid of the core storage disk for both the internal and external disk to be present at the same time. I tested the external disk on a different mac and it works perfectly. I have not tried to change the UUID as my idea is to now wipe the internal disk anyway.

I used dd to make a clone and verified the md5 sums.

At boot, I can choose from all the expected volumes: "Untitled", "Windows", and with external-disk-symbol: "Untitled", "Windows".

Regardless of which "Untitled" I choose, it ends up booting up using the internal disk. Any ideas as to why? How I could I fix it?

How I made the clone:

I booted into Linux from a USB stick, no other filesystem was mounted, I proceeded to make the copy:

dd if=/dev/sda of=/dev/sdc bs=4096 conv=noerror,sync

I verified that the md5 sums of the entire /dev/sda matched the equivalent size on /dev/sdc.

Info about the disks

Once in OS X (from the internal disk using "Untitled"), this is what I see with diskutil list:

$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *751.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Untitled                689.4 GB   disk0s2
   3:                 Apple_Boot Boot OS X               650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                61.0 GB    disk0s4

/dev/disk1 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER

            Untitled               +689.1 GB   disk1
                             Logical Volume on disk0s2
                             Unlocked Encrypted

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:          Apple_CoreStorage                         689.4 GB   disk2s2
   3:                 Apple_Boot Boot OS X               650.0 MB   disk2s3
   4:       Microsoft Basic Data BOOTCAMP                61.0 GB    disk2s4

In Disk Utility the only volume that shows up for /dev/disk2 is BOOTCAMP.


Running fsck_cs on both disk2s2 (the external disk's core storage) and on disk0s2 (the internal disk's core storage), I get equivalent output and the volume seems fine.

Perhaps the issue is that there are two volumes (on different disks) with the same UUUD? (9EE93F75-E7F0-40C2-B562-6A8733A6EB16)

$ sudo fsck_cs -n -l log.txt disk2s2
   Executing fsck_cs (version 540.30.1)
** Checking volume
** disk2s2: Scan for Volume Headers
** disk2s2: Scan for Disk Labels
** Logical Volume Group 9EE93F75-E7F0-40C2-B562-6A8733A6EB16 on 1 device
** disk2s2: Scan for Metadata Volume
** Logical Volume Group has a 17 MB Metadata Volume with double redundancy
** Start scanning metadata for a valid checkpoint
** Load and verify Segment Headers
** Load and verify Checkpoint Payload
** Load and verify Transaction Segment
** Load and verify Transaction Segment
** Incorporate 1 newer non-checkpoint transaction
** Load and verify Virtual Address Table
** Load and verify Segment Usage Table
** Load and verify Metadata Superblock
** Load and verify Logical Volumes B-Trees
** Logical Volume Group contains 1 Logical Volume
** Load and verify 4F52DBC8-6A69-4099-82B4-5E437C4CEA74
** Load and verify 137B561F-8819-4ABD-BFBF-DD8F3A997D60
** Load and verify Freespace Summary
** Load and verify Block Accounting
** Load and verify Live Virtual Addresses
** Newest transaction commit checkpoint is valid
** Load and verify Segment Cleaning
** The volume 9EE93F75-E7F0-40C2-B562-6A8733A6EB16 appears to be OK
  • Your cloned LVGs on disk2s2 and disk0s2 have identical UUIDs for LVG/PV/LVF/LV. This will fail because each has to be unique. Booting to Windows on an external USB drive usually also fails! – klanomath Apr 28 '17 at 8:59
  • @klanomath thanks, any ideas how I can change the UUIDs? – j-a Apr 28 '17 at 9:03
  • The UUIDs can be changed by disabling and enabling FileVault on one of the volumes - which will take some time.... (either the internal one while the external is unplugged or detaching the internal one and converting the external volume) – klanomath Apr 28 '17 at 9:07
  • @klanomath, if you make it an answer I'll accept it. – j-a Apr 29 '17 at 9:53

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