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I formated a external USB drive to mount with 10 different volumes. (Actually I forgot how i made this work)

The drive will not show as being partitioned in drive utility in OSX but show all volumes(MBR) on this drive as kind of individual ones which are not related like partitions are.

With diskutil in terminal I was able to delete the unnecessary volumes. But now I have a 2TB drive with only two volumes left, which share 400GB together. So the unallocated space is missing and I do not know how to reallocate it either asigning it to one of the volumes or by creating a new volume which takes all unalloacted space. Does anybody know what to do?

I would realy want to avoid erasing the whole disk, as the two volumes keep backups of different machines.

Disk

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *2.0 TB     disk2
   1:                  Apple_HFS Name1                200.2 GB   disk2s1
   2:                  Apple_HFS Name2                200.2 GB   disk2s5

sudo gpt -r show disk2

       start        size  index  contents
           0           1         MBR
           1   390965066         
   390965067   390965064      1  MBR part 175
   781930131  2345790390      2  MBR part 5
  3127720521   779308647  

Is there any way to keep the two left volumes and allocate the free space?

Best, hirschferkel

Disk: /dev/disk2    geometry: 243201/255/63 [3907029168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: AF 1023 254  63 - 1023 254  63 [ 390965067 -  390965064] HFS+        
 2: 05 1023 254  63 - 1023 254  63 [ 781930131 - 2345790390] Extended DOS
 3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: AF 1023 254  63 - 1023 254  63 [2736755457 -  390965064] HFS+        
 2: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused  
  • Since the disk is using a MBR partition scheme, it would be helpful if you could include the output from fdisk /dev/disk2. – David Anderson Apr 4 at 20:08
  • @DavidAnderson I updated my question with the output. Best – Hirschferkel Apr 5 at 9:18
  • What version of macOS are you using? How do you want the space allocated? Do you want to keep the legacy MBR table partitioning the disk is currently using? Or, do you want to convert to use the more modern GUID Partition Table (GPT)? – David Anderson Apr 5 at 11:28
  • @DavidAnderson Hi David, thanks for your help. As the volumes contain OSX backups I do not know if it is possible to convert these volumes into partitions of a gpt type and keep them working? If it is, I do not need the MBR tables anymore. I'm currently running OSX 10.13.6. It would be possible to use a GPT table, if it does not mean to erase the disk. If it is possible to transform the two volumes into two partitions wich work as the backup destination, would be perfect. So my only concers are to keep the backups working. Anything else is possible to change. – Hirschferkel Apr 5 at 12:42
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The procedure posted in this answer relies on the use of the command gdisk. The command is not included with macOS. Included is the procedure for installing this command.

Note: Disk identifiers (disk2 for example) and partition identifiers (disk2s1 for example) can be set arbitrarily by macOS. I tried to post the correct identifiers. Before executing a command, you may want to review the output from diskutil list to insure the correct identifier is being used.

Install gdisk

  1. Download gdisk from the internet. I assume this will be downloaded to your Downloads folder.
  2. Execute the command given below to remove the quarantine.

    xattr -d com.apple.quarantine ~/Downloads/gdisk-1.0.4.pkg
    
  3. Use the Finder application to install gdisk.

Convert a MBR Partition Table to a GUID Partition Table (GPT).

Note: Not all drives using a MBR Partition Table can be converted to use a GUID Partition Table (GPT). The drive posted in the OP's question happens a drive that can be easily converted.

  1. Use command given below to determine the identifier for the drive. I will assume this is disk2, as shown in your question.

    diskutil list
    
  2. Execute the following commands to perform the conversion.

    diskutil unmountdisk disk2
    gdisk /dev/disk2
    w
    y
    

    Below is an example.

    $ diskutil unmountdisk disk2
    Unmount of all volumes on disk2 was successful
    $ gdisk /dev/disk2
    GPT fdisk (gdisk) version 1.0.4
    
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Partition table scan:
      MBR: MBR only
      BSD: not present
      APM: not present
      GPT: not present
    
    
    ***************************************************************
    Found invalid GPT and valid MBR; converting MBR to GPT format
    in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
    typing 'q' if you don't want to convert your MBR partitions
    to GPT format!
    ***************************************************************
    
    
    Command (? for help): w
    
    Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
    PARTITIONS!!
    
    Do you want to proceed? (Y/N): y
    OK; writing new GUID partition table (GPT) to /dev/disk2.
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Warning: The kernel may continue to use old or deleted partitions.
    You should reboot or remove the drive.
    The operation has completed successfully.
    
  3. Eject the drive by executing the command given below.

    diskutil eject disk2
    
  4. Unplug the drive and plug back in. Execute the command below to see if the drive identifier has changed.

    diskutil list
    

Add an EFI Partition

Note: The defaults shown in the examples may not match what you will see.

  1. Create the partition. Selecting a partition type of Linux prevents the partition from mounting before being formatted.

    diskutil unmountdisk disk2
    gdisk /dev/disk2
    s
    n
    3
    40
    409639
    8300
    s
    w
    y
    

    Below is an example.

    $ diskutil unmountdisk disk2
    Unmount of all volumes on disk2 was successful
    $ gdisk /dev/disk2
    GPT fdisk (gdisk) version 1.0.4
    
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Partition table scan:
      MBR: protective
      BSD: not present
      APM: not present
      GPT: present
    
    Found valid GPT with protective MBR; using GPT.
    
    Command (? for help): s
    You may need to edit /etc/fstab and/or your boot loader configuration!
    
    Command (? for help): n
    Partition number (2-128, default 2): 3
    First sector (34-3906250006, default = 40) or {+-}size{KMGTP}: 40
    Last sector (40-409639, default = 409639) or {+-}size{KMGTP}: 409639
    Current type is 'Apple HFS/HFS+'
    Hex code or GUID (L to show codes, Enter = AF00): 8300
    Changed type of partition to 'Linux filesystem'
    
    Command (? for help): s
    You may need to edit /etc/fstab and/or your boot loader configuration!
    
    Command (? for help): w
    
    Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
    PARTITIONS!!
    
    Do you want to proceed? (Y/N): y
    OK; writing new GUID partition table (GPT) to /dev/disk2.
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Warning: The kernel may continue to use old or deleted partitions.
    You should reboot or remove the drive.
    The operation has completed successfully.
    
  2. Eject the drive by executing the command given below.

    diskutil eject disk2
    
  3. Unplug the drive and plug back in. Execute the command below to see if the drive identifier has changed.

    diskutil list
    
  4. FAT32 format the partition.

    newfs_msdos -F 32 -v EFI /dev/rdisk2s1
    

    Below is an example.

    $ newfs_msdos -F 32 -v EFI /dev/rdisk2s1
    512 bytes per physical sector
    /dev/rdisk2s1: 403266 sectors in 403266 FAT32 clusters (512 bytes/cluster)
    bps=512 spc=1 res=32 nft=2 mid=0xf8 spt=32 hds=32 hid=40 drv=0x80 bsec=409600 bspf=3151 rdcl=2 infs=1 bkbs=6
    
  5. Change the partition type to EFI.

    diskutil unmountdisk disk2
    gdisk /dev/disk2
    t
    1
    EF00
    w
    y
    

    Below is an example.

    $ diskutil unmountdisk disk2
    Unmount of all volumes on disk2 was successful
    $ gdisk /dev/disk2
    GPT fdisk (gdisk) version 1.0.4
    
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Partition table scan:
      MBR: protective
      BSD: not present
      APM: not present
      GPT: present
    
    Found valid GPT with protective MBR; using GPT.
    
    Command (? for help): t
    Partition number (1-2): 1
    Current type is 'Linux filesystem'
    Hex code or GUID (L to show codes, Enter = AF00): EF00
    Changed type of partition to 'EFI System'
    
    Command (? for help): w
    
    Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
    PARTITIONS!!
    
    Do you want to proceed? (Y/N): y
    OK; writing new GUID partition table (GPT) to /dev/disk2.
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Warning: The kernel may continue to use old or deleted partitions.
    You should reboot or remove the drive.
    The operation has completed successfully.
    

Add a New Mac OS Extended (Journaled) Volume

The free space before the original two volumes can not be added to either of these volumes. To reclaim this space, one or more new volumes need to be created. The procedure below creates one new volume.

  1. Create the partition. Selecting a partition type of Linux prevents the partition from mounting before being formatted.

    diskutil unmountdisk disk2
    gdisk /dev/disk2
    n
    4
    409640
    69999999
    8300
    s
    w
    y
    

    Below is an example.

    $ diskutil unmountdisk disk2
    Unmount of all volumes on disk2 was successful
    $ gdisk /dev/disk2
    GPT fdisk (gdisk) version 1.0.4
    
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Partition table scan:
      MBR: protective
      BSD: not present
      APM: not present
      GPT: present
    
    Found valid GPT with protective MBR; using GPT.
    
    Command (? for help): n
    Partition number (2-128, default 2): 4
    First sector (34-3906250006, default = 409640) or {+-}size{KMGTP}: 409640
    Last sector (409640-3906250006, default = 3906250006) or {+-}size{KMGTP}: 69999999
    Current type is 'Apple HFS/HFS+'
    Hex code or GUID (L to show codes, Enter = AF00): 8300
    Changed type of partition to 'Linux filesystem'
    
    Command (? for help): s
    You may need to edit /etc/fstab and/or your boot loader configuration!
    
    Command (? for help): w
    
    Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
    PARTITIONS!!
    
    Do you want to proceed? (Y/N): y
    OK; writing new GUID partition table (GPT) to /dev/disk2.
    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Warning: The kernel may continue to use old or deleted partitions.
    You should reboot or remove the drive.
    The operation has completed successfully.
    
  2. Eject the drive by executing the command given below.

    diskutil eject disk2
    
  3. Unplug the drive and plug back in. Execute the command below to see if the drive identifier has changed.

    diskutil list
    
  4. Format the partition Mac OS Extended (Journaled). This will also change the partition type to the correct value.

    diskutil erasevolume jhfs+ Name3 disk2s2
    

    Below is an example.

    $ diskutil erasevolume jhfs+ Name3 disk2s2
    Started erase on disk2s2 My2TB
    Unmounting disk
    Erasing
    Initialized /dev/rdisk2s2 as a 33 GB case-insensitive HFS Plus volume with a 8192k journal
    Mounting disk
    Finished erase on disk2s2 Name3
    

Reclaim the Remaining Free Space

Add the remaining free space to the existing Volumes. Any free space that is remaining after entering these commands should be fairly small and is required to be reserved for use by macOS.

    diskutil resizevolume disk2s2 R
    diskutil resizevolume disk2s3 R
    diskutil resizevolume disk2s4 R

Below is an example.

    $ diskutil resizevolume disk2s2 R
    Unable to find disk for disk2s2
    $ diskutil resizevolume disk2s2 R
    Resizing to full size (fit to fill)
    Started partitioning on disk2s2 Name3
    Verifying the disk
    Verifying file system
    Volume was successfully unmounted
    Performing fsck_hfs -fn -x /dev/rdisk2s2
    Checking Journaled HFS Plus volume
    Checking extents overflow file
    Checking catalog file
    Checking multi-linked files
    Checking catalog hierarchy
    Checking extended attributes file
    Checking volume bitmap
    Checking volume information
    The volume Name3 appears to be OK
    File system check exit code is 0
    Restoring the original state found as mounted
    Resizing
    Modifying partition map
    Growing file system
    Finished partitioning on disk2s2 Name3
    /dev/disk2 (external, physical):
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *2.0 TB     disk2
       1:                        EFI EFI                     209.7 MB   disk2s1
       2:                  Apple_HFS Name3                   199.8 GB   disk2s2
       3:                  Apple_HFS Name1                   200.2 GB   disk2s3
       4:                  Apple_HFS Name2                   200.2 GB   disk2s4
    $ diskutil resizevolume disk2s3 R
    Resizing to full size (fit to fill)
    Started partitioning on disk2s3 Name1
    Verifying the disk
    Verifying file system
    Volume was successfully unmounted
    Performing fsck_hfs -fn -x /dev/rdisk2s3
    Checking Journaled HFS Plus volume
    Checking extents overflow file
    Checking catalog file
    Checking multi-linked files
    Checking catalog hierarchy
    Checking extended attributes file
    Checking volume bitmap
    Checking volume information
    The volume Name1 appears to be OK
    File system check exit code is 0
    Restoring the original state found as mounted
    Resizing
    Modifying partition map
    Growing file system
    Finished partitioning on disk2s3 Name1
    /dev/disk2 (external, physical):
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *2.0 TB     disk2
       1:                        EFI EFI                     209.7 MB   disk2s1
       2:                  Apple_HFS Name3                   199.8 GB   disk2s2
       3:                  Apple_HFS Name1                   1.2 TB     disk2s3
       4:                  Apple_HFS Name2                   200.2 GB   disk2s4
    $ diskutil resizevolume disk2s4 R
    Resizing to full size (fit to fill)
    Started partitioning on disk2s4 Name2
    Verifying the disk
    Verifying file system
    Volume was successfully unmounted
    Performing fsck_hfs -fn -x /dev/rdisk2s4
    Checking Journaled HFS Plus volume
    Checking extents overflow file
    Checking catalog file
    Checking multi-linked files
    Checking catalog hierarchy
    Checking extended attributes file
    Checking volume bitmap
    Checking volume information
    The volume Name2 appears to be OK
    File system check exit code is 0
    Restoring the original state found as mounted
    Resizing
    Modifying partition map
    Growing file system
    Finished partitioning on disk2s4 Name2
    /dev/disk2 (external, physical):
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *2.0 TB     disk2
       1:                        EFI EFI                     209.7 MB   disk2s1
       2:                  Apple_HFS Name3                   199.8 GB   disk2s2
       3:                  Apple_HFS Name1                   1.2 TB     disk2s3
       4:                  Apple_HFS Name2                   598.6 GB   disk2s4

Appendix

Descriptions for the gdisk commands is given below.

b   back up GPT data to a file
c   change a partition's name
d   delete a partition
i   show detailed information on a partition
l   list known partition types
n   add a new partition
o   create a new empty GUID partition table (GPT)
p   print the partition table
q   quit without saving changes
r   recovery and transformation options (experts only)
s   sort partitions
t   change a partition's type code
v   verify disk
w   write table to disk and exit
x   extra functionality (experts only)
?   print this menu
  • Wow... That was great! It worked out perfectly and I was additionally able to make some changes differently to my needs due to your great tutorial... thanks a lot! – Hirschferkel Apr 8 at 11:03

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