Can I resize the macOS High Sierra HDD partition without losing data or making dual boot unusable?

There are two disks with a 500GB capacity:

➜  ~  diskutil list        
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *240.1 GB   disk0
   1:               Windows_NTFS SSD                     239.2 GB   disk0s1
   2:                       0x27                         900.7 MB   disk0s2

/dev/disk1 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS HDD                     307.4 GB   disk1s2
   3:                 Apple_Boot                         650.0 MB   disk1s3
   4:       Microsoft Basic Data BOOT                    41.7 GB    disk1s4
   5:       Microsoft Basic Data DOX                     150.0 GB   disk1s5

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:       Microsoft Basic Data                         306.2 GB   disk2s2
   3:       Microsoft Basic Data                         42.0 GB    disk2s3
   4:                  Apple_HFS                         134.2 MB   disk2s4
   5:       Microsoft Basic Data Copy of C               150.0 GB   disk2s5
   6:       Microsoft Basic Data New Volume              1.4 GB     disk2s6

disk1 is the internal one, on which macOS runs

disk2 is the external LaCie disk

➜  ~  sudo fdisk /dev/disk2

Disk: /dev/disk2 geometry: 60801/255/63 [976773168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -  976773167] <Unknown ID>
 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     

Repairing the partition map might erase disk2s1, proceed? (y/N) y
Started partition map repair on disk2
Checking prerequisites
Checking the partition list
Adjusting partition map to fit whole disk as required
Checking for an EFI system partition
Checking the EFI system partition's size
Checking the EFI system partition's file system
Checking the EFI system partition's folder content
Checking all HFS data partition loader spaces
Checking booter partitions
Reviewing boot support loaders
Checking Core Storage Physical Volume partitions
The partition map appears to be OK
Finished partition map repair on disk2


➜  ~  diskutil list            
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *240.1 GB   disk0
   1:               Windows_NTFS SSD                     239.2 GB   disk0s1
   2:                       0x27                         900.7 MB   disk0s2

/dev/disk1 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS HDD                     307.4 GB   disk1s2
   3:                 Apple_Boot                         650.0 MB   disk1s3
   4:       Microsoft Basic Data BOOT                    41.7 GB    disk1s4
   5:       Microsoft Basic Data DOX                     150.0 GB   disk1s5

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:       Microsoft Basic Data                         306.2 GB   disk2s2
   3:       Microsoft Basic Data                         42.0 GB    disk2s3
   4:                  Apple_HFS                         134.2 MB   disk2s4
   5:       Microsoft Basic Data Copy of C               150.0 GB   disk2s5
   6:       Microsoft Basic Data New Volume              1.4 GB     disk2s6

Unmounted and remounted the disk and the same 2 partitions show up, 2 remain missing.

➜  ~  df -h


Filesystem      Size   Used  Avail Capacity iused      ifree %iused  Mounted on
/dev/disk1s2   286Gi  174Gi  112Gi    61% 1529788 4293437491    0%   /
devfs          193Ki  193Ki    0Bi   100%     668          0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%       0          0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%       0          0  100%   /home
/dev/disk0s1   223Gi  156Gi   67Gi    70%  683437   70836643    1%   /Volumes/SSD
/dev/disk1s4    39Gi   86Mi   39Gi     1%      40   40614752    0%   /Volumes/BOOT
/dev/disk1s5   139Gi  115Gi   24Gi    83%   38402   25606958    0%   /Volumes/DOX
/dev/disk2s6   1.3Gi   21Mi  1.3Gi     2%      43    1359525    0%   /Volumes/New Volume
/dev/disk2s5   140Gi   77Gi   63Gi    56%  475069   65767499    1%   /Volumes/Copy of C

➜  ~  mount -v


/dev/disk1s2 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk0s1 on /Volumes/SSD (ntfs, local, read-only, noowners)
/dev/disk1s4 on /Volumes/BOOT (ntfs, local, read-only, noowners)
/dev/disk1s5 on /Volumes/DOX (ntfs, local, read-only, noowners)
/dev/disk2s6 on /Volumes/New Volume (ntfs, local, read-only, noowners)
/dev/disk2s5 on /Volumes/Copy of C (ntfs, local, read-only, noowners)

➜  ~  sudo gdisk -l /dev/disk2
Password:
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.
Disk /dev/disk2: 976773168 sectors, 465.8 GiB
Sector size (logical): 512 bytes
Disk identifier (GUID): 287BB89D-9276-4D6D-8DBA-2B32583F9A77
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 976773134
Partitions will be aligned on 8-sector boundaries
Total free space is 264853 sectors (129.3 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              40          409639   200.0 MiB   EF00  EFI System Partition
   2          409640       598485743   285.2 GiB   0700  Backup
   3       598747888       680779135   39.1 GiB    0700  Backup 2
   4       680779776       681041919   128.0 MiB   AF00  Basic data partition
   5       681041920       974010367   139.7 GiB   0700  
   6       974010368       976771071   1.3 GiB     0700  Basic data partition
➜  ~  diskutil mount disk2s1
Volume EFI on disk2s1 mounted
➜  ~  diskutil mount disk2s2 
Volume on disk2s2 failed to mount
If the volume is damaged, try the "readOnly" option
➜  ~  diskutil mount disk2s3
Volume on disk2s3 failed to mount
If the volume is damaged, try the "readOnly" option

Only the EFI partition has mounted and is visible now, next to the other 2 that were already visible.

I've checked both on Windows and macOS and I'm not seeing any NTFS driver installed right now.

However, I remember at some point there was an issue with macOS drives not displaying in Windows, so I installed an NTFS driver on Windows to be able to see macOS drives again. It was causing some issues, so eventually I disabled it by using some tool provided by Microsoft on their site which allowed selective disabling of drivers. I've been searching through registry, folders, files, services (running or disabled) etc but I didn't find any trace of an NTFS driver currently installed. The reason why I'm not finding any trace might be because the NTFS driver may have not been installed on the current Windows 10 system, on the SSD drive.

That driver was probably installed when both the macOS system and the Windows system were installed on the same internal hard-disk drive. The internal hard disk basically had a hybrid layout which was likely to run into issues at each system update, so eventually I decided to buy an SSD and install Windows on it, to make sure I keep separate OSes on separate physical disks. That hybrid layout has been broken once or twice and I had to fix it with GPT fdisk.

At some point, some partitions from this hybrid layout internal hard-disk have been cloned on the LaCie external drive (which might explain why there are some EFI and Apple_HFS partitions on it). I had the intention to simplify the layout of this external disk by moving all the data from it, erasing it and reformatting it, but didn't have a bigger spare backup drive back then to be able to move the data. Now I have a 2TB spare drive but can't access the data on the LaCie drive (the 2 partitions which are visible don't have any significant data).

It's possible that the NTFS driver that was installed on the internal hard disk at some point may have produced some effects on the logical layout of the disk and that this High Sierra update might have collided with that older layout somehow. But even if some of the internal hard-disk partitions have been cloned on the external LaCie drive (in a form that may have been impacted by the NTFS driver), I'm not sure whether the High Sierra update could have made those 2 partitions unreadable, or if the cause is unrelated.

So, at the moment, I don't think there is any active third-party NTFS driver installed on the SSD Windows partition or on the macOS partition, but there may have been one installed on the internal hard drive in the past.

And since some partitions from it have been cloned on the external drive too, this could have left some marks on how partitions are laid out on the external drive too.

So while I see a clear connection between the recent High Sierra update and the DOX internal hard-disk partition disappearing on Windows, not sure there's a clear connection with those 2 partitions on the external drive not showing up.

I don't have a non-Apple PC right now to test on. I've tested on another, older macmini and they don't show up.

And, of course, I've tested on the Windows system on this macmini and it's the same situation.

➜  ~  sudo dd if=/dev/disk2s2 count=5 2>/dev/null | hexdump -C


00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400  48 2b 00 04 80 00 21 00  48 46 53 4a 00 00 0e 8d  |H+....!.HFSJ....|
00000410  d0 8e 9d c9 d4 e2 6f db  00 00 00 00 d0 8e 81 a9  |......o.........|
00000420  00 0f d3 12 00 03 16 d4  00 00 10 00 04 74 bd 59  |.............t.Y|
00000430  02 97 08 91 01 ed 15 87  00 01 00 00 00 01 00 00  |................|
00000440  00 12 ea e5 00 10 0e cc  00 00 00 00 02 20 00 fb  |............. ..|
00000450  00 0b 1c b0 00 0b be ca  00 00 00 00 00 00 00 00  |................|
00000460  00 00 00 00 00 0b 1c b0  07 0e 16 8c 0b 0c f6 dc  |................|
00000470  00 00 00 00 00 e8 c0 00  00 e8 c0 00 00 00 0e 8c  |................|
00000480  00 00 00 01 00 00 0e 8c  00 00 00 00 00 00 00 00  |................|
00000490  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000004c0  00 00 00 00 00 90 00 00  00 90 00 00 00 00 09 00  |................|
000004d0  00 00 36 8e 00 00 09 00  00 00 00 00 00 00 00 00  |..6.............|
000004e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000510  00 00 00 00 1f b0 00 00  0a 90 00 00 00 01 fb 00  |................|
00000520  00 08 95 8e 00 01 fb 00  00 00 00 00 00 00 00 00  |................|
00000530  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000560  00 00 00 00 24 60 00 00  0c 20 00 00 00 02 46 00  |....$`... ....F.|
00000570  00 00 3f 8e 00 02 46 00  00 00 00 00 00 00 00 00  |..?...F.........|
00000580  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000a00

➜  ~  sudo dd if=/dev/disk2s3 count=5 2>/dev/null | hexdump -C
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400  48 2b 00 04 80 00 21 00  48 46 53 4a 00 00 01 3a  |H+....!.HFSJ...:|
00000410  d0 8e b2 72 d4 e2 92 5a  00 00 00 00 d0 8e 96 52  |...r...Z.......R|
00000420  00 04 46 d7 00 00 fd 33  00 00 10 00 00 9c 76 52  |..F....3......vR|
00000430  00 6b 3b 57 00 39 00 21  00 01 00 00 00 01 00 00  |.k;W.9.!........|
00000440  00 05 44 c4 00 02 59 45  00 00 00 00 02 20 00 fb  |..D...YE..... ..|
00000450  00 01 6f cf 00 01 fd b9  00 00 00 00 00 00 00 00  |..o.............|
00000460  00 00 00 00 00 01 6f cf  18 ca 01 dd f2 7a 55 df  |......o......zU.|
00000470  00 00 00 00 00 13 90 00  00 13 90 00 00 00 01 39  |...............9|
00000480  00 00 00 01 00 00 01 39  00 00 00 00 00 00 00 00  |.......9........|
00000490  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000004c0  00 00 00 00 00 60 00 00  00 60 00 00 00 00 06 00  |.....`...`......|
000004d0  00 00 09 3b 00 00 06 00  00 00 00 00 00 00 00 00  |...;............|
000004e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000510  00 00 00 00 09 30 00 00  03 10 00 00 00 00 93 00  |.....0..........|
00000520  00 03 ab 3b 00 00 93 00  00 00 00 00 00 00 00 00  |...;............|
00000530  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000560  00 00 00 00 0f c0 00 00  05 40 00 00 00 00 fc 00  |.........@......|
00000570  00 00 0f 3b 00 00 fc 00  00 00 00 00 00 00 00 00  |...;............|
00000580  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000a00

GPT fdisk is installed, yes.

Well as long as it's possible to make any OS read these partitions so I can recover the data, it's fine. I have a new, recently bought 2TB external drive that can be used to back up those data.

Then I can format this external disk to simplify its layout and fix all these logical inconsistencies.

It worked. 👌

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:                  Apple_HFS Backup                  306.2 GB   disk2s2
   3:                  Apple_HFS Lion                    42.0 GB    disk2s3
   4:                  Apple_HFS                         134.2 MB   disk2s4
   5:       Microsoft Basic Data Copy of C               150.0 GB   disk2s5
   6:       Microsoft Basic Data New Volume              1.4 GB     disk2s6

Now I can see the data. But I cannot write to any disk that was formatted as NTFS.

Is there any file system on which both macOS and Windows can write and read? Apparently exFAT is unstable and corruption-prone. Not sure how FAT16 or FAT32 support is now on macOS High Sierra and Windows 10. I'm looking for a way to transfer these data between systems.

Thanks for the help. Once I manage to transfer the data I might be able to follow your suggestion to create a TM backup on the reformatted LaCie external HDD and use the Recovery mode to re-partition the internal HDD and restore macOS from the external drive.

OK, I have saved all the relevant data from the external LaCie drive, so I can format it now to be used with Time Machine. Should I first erase the whole disk, in order to make sure it will also fix its partition scheme?

I was thinking of creating 2 partitions only this time: one for TM backups and a smaller one to move some documents over to Windows. Which partition scheme could work for that? GUID, MBR or APM?

I've so had it with this fragile, flaky dual-boot BS. It took macOS more than an hour to load again, after I got out of Recovery mode, without changing anything (I couldn't repartition the internal hdd). Then I could not boot in any system at all, Command-R after boot wasn't working either, so I couldn't get in Recovery to use the terminal to bless the Windows drive and reboot in Win10. So I was stuck waiting for macOS to load itself again in a slower-than-molasses mode. Last time I loaded it, it took just a few seconds. After finally loading the system, I noticed it changed the audio output device to the macmini internal speaker. And all this thanks to just booting in Recovery mode and not changing anything.

Can't you guys call Microsoft one day, get around a table and agree to some common, solid solution to these file system collisions, that keep happening over and over and over again, after each OS update. It cost me a few days of productivity already.

I'm close to just nuking this macOS partition and simplifying things. Every time there's an update, I have to come here and ask for your help to fix the drives with GPT fdisk or even to reinstall one or both systems.

This is going to be the last time I'll use dual boot Windows-macos. It's just not a sustainable configuration, unless Apple and Microsoft decide to implement a more robust solution.