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I was testing out a Linux Mint installation on an iMac in order to run some programs written for Linux. This iMac was a dual boot with Windows installed through bootcamp. I think it corrupted the boot system for Windows (The MBR and hybrid MBR is confusing me).

I thought of removing the Linux installation and thus I used Disk Utility and reformatted and removed the Linux partitions.

However, when I list the disk, the (internal, virtual) and Recovery HD drive is missing since after the removing the first installation.

Currently I repartition the drives and reinstall Linux Mint to run the required program. I would like to ask for help with the following:

  1. What is the internal, virtual drive? And why is it and the recovery HD missing? (I want to know what I did wrong)

  2. Does the missing internal, virtual drive need fixing? How to do it?

  3. Is it possible to fix Windows boot in without reinstalling it?

    • I am actually fine with dual boot for now and lose the Windows. If I need to I would follow the guide on triple booting (which I saw after this had happened). But if there is a way to fix it please let me know.

Here is the readout from disk util when I formatted it for the first linux installation

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macintosh HD            250.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data                         649.9 GB   disk0s4
   5:       Microsoft Basic Data                         18.9 GB    disk0s5
   6:       Microsoft Basic Data                         29.9 GB    disk0s6
   7:       Microsoft Basic Data BOOTCAMP                50.0 GB    disk0s7

/dev/disk1 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                            Macintosh HD           +250.0 GB   disk1
                             Logical Volume on disk0s2
                             A2849F4D-66EA-4FFF-8FB2-5247B5407C0C
                             Unencrypted

After that I formatted and remove the linux partition of MacOS disk utility.I formatted partition 4,5 and 6 and resize with the Macintosh HD partition. Now it reads

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            949.9 GB   disk0s2
   3:       Microsoft Basic Data BOOTCAMP                50.0 GB    disk0s3



gpt show: disk0: Suspicious MBR at sector 0
       start        size  index  contents
           0           1         MBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6         
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640  1855197144      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
   1855606784     262144
   1855868928   97654784      3  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
   1953523712       1423        
  1953525135          32         Sec GPT table
  1953525167           1         Sec GPT header

I repartition and installed linux mint again with a Home drive, a OS drive and a swap drive.

Now this is what the disk util reads:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            250.0 GB   disk0s2
   3:       Microsoft Basic Data                         649.9 GB   disk0s3       
   4:       Microsoft Basic Data                         14.9 GB    disk0s4
   5:       Microsoft Basic Data                         34.7 GB    disk0s5
   6:       Microsoft Basic Data BOOTCAMP                50.0 GB    disk0s6


gpt show: disk0: Suspicious MBR at sector 0
       start        size  index  contents
           0           1         MBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6         
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640  1855197144      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
   488690888      262144
   488953032  1269269104      3  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7                      
  1758222136      262144
  1758484280    29034728      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7                                                                              
  1787519008      262144
  1787781152    67825632      5  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7                      
  1855606784      262144 
  1855868928    97654784      6  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  1953523712        1423        
  1953525135          32         Sec GPT table
  1953525167           1         Sec GPT header
  • Your are still messing with your down under Mac ;-). In my opinion it's almost impossible to explain how this mess happened without the commands entered in the shell or the steps taken in Disk Utility or other similar tools in Mint/Windows. Is this the same Mac as the one in your other question? – klanomath Dec 31 '16 at 2:41
  • Haha. This is a different iMac. I do not remember the full steps. I did not do anything in shell, just partitioning and formatting with disk utility and installing mint. In the end I just need to run some bioinformatics programs written for Linux off a local machine instead of a server. So I am trying to dual boot linux. The first machine had issues with the hardware I think (graphic card) so I simply restored that one. This other iMac supports mint but I did not put the bootcamp into consideration. Good news is I back up all the important data. – Shkgma Dec 31 '16 at 3:49
  • I recommend VMware/Parallels/VirtualBox or maybe brew/science. What's the name of the bioinformatics app? – klanomath Dec 31 '16 at 4:01
  • I am trying to run fusion catcher and soap-fuse. A lot of these are resource intensive so is I am not sure if VMware/parallels/VirtualBox might be appropriate. I am unfamiliar with brew/science. I thought a dual boot system would be easy. Apparently not... :( – Shkgma Dec 31 '16 at 4:12
  • FusionCatcher should run natively on macOS. All files are py and the dependencies (e.g. bowtie/bowtie2/...) are available via brew/science or macports – klanomath Dec 31 '16 at 4:28
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  1. The internal virtual disk is a Logical Volume and part of a CoreStorage Logical Volume Group. CoreStorage itself is a logical volume manager similar to Linux' LVM. An LVM is an additional abstraction layer in between hard disks and partitions on one side and volumes on the other side.

    In macOS you can convert a partition (e.g disk0s2) with a HFS+ file system lossless to a Logical Volume Group which initially contains several nested items: a Physical Volume, a Logical Volume Family and a Logical Volume. The final Logical Volume is slightly smaller than the original partition, because CoreStorage needs some space to save administrative data.

    The Logical Volume contains the data of the previous standard volume/partition and is mapped to its own (virtual) disk device: disk0s2 > disk1

    If your Logical Volume disk1 contains a lot of free space you may resize it and add a second Logical Volume in the same Physical Volume and after formatting it you will get a second virtual device: disk0s2 > disk2

    If you have a second physical partition on your main disk or a second disk with a partition you may add either or all of them to the first Logical Volume Group. They will be added to the total space available in the Logical Volume Group. You may also create a second Logical Volume Group.

    If you have added a second partition (= Physical Volume) to the LVG you can expand the initial Logical Volume to span both Physical Volumes. If the second partition is on a different disk (SSD) this is called a "Fusion Drive". If the second Physical Volume is on the same drive it's a fake Fusion Drive. If you additionally add a partition on a third drive it's a Uber Fusion Drive.

    Depending on how you created the LVG you can revert a 1(LVG):1(PV):1(LVF):1(LV) to a normal volume. This is not possible with an e.g. 1:2:1:1 or 1:2:1:2 LVG because you can't map 1(LV)→ 2(HFS+-volumes) (~technically-mathematically).

    Another feature of CoreStorage is volume encryption > FileVault2.

  2. The "missing internal, virtual drive" doesn't need fixing because it's not missing but was converted to a normal partition/HFS+ volume again (see 1.)

    The Recovery HD partition probably got deleted while installing Mint.

  3. The main problem of your partition table is the MBR and its restrictions (four entries). Your Windows partition resides on the sixth partition which is actually not included in the MBR. You may fix this by following one of the many of David Anderson's answers related to MBR/PMBR/multi boot.
  • Thanks for the detailed explanation. Always cool to learn something new. :) But am still a total newb with such stuff. The learning curve is tough. I will look up the post with regards to MBR/PMBR/multiboot. Is the recovery HD for booting into recovery locally and different from Internet recovery (through the net?). Is there a need to fix the recovery HD? – Shkgma Dec 31 '16 at 4:35
  • @Shkgma The Recovery HD is not absolutely essential. Recovery Mode (cmd-R) boots to a base OS X image in the Recovery HD; Internet Recovery Mode (alt-cmd-R) boots to a basic OS X netboot image served by Akamai/Apple via Internet. – klanomath Dec 31 '16 at 4:43

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