Resize Mac Partition after bootcamp, snapshot limitation

Question

I'd like to add a 30GB exFat partition as a shared area accessible from both windows and macOS. Using the bootcamp utility the disks currently looks like this:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI ⁨EFI⁩                     314.6 MB   disk0s1
   2:                 Apple_APFS ⁨Container disk1⁩         361.0 GB   disk0s2
                    (free space)                         10.0 GB    -
   3:       Microsoft Basic Data ⁨BOOTCAMP⁩                129.0 GB   disk0s3
/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +361.0 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume ⁨Macintosh HD - Data⁩     245.5 GB   disk1s1
   2:                APFS Volume ⁨Preboot⁩                 431.1 MB   disk1s2
   3:                APFS Volume ⁨Recovery⁩                1.1 GB     disk1s3
   4:                APFS Volume ⁨VM⁩                      1.1 GB     disk1s4
   5:                APFS Volume ⁨Macintosh HD⁩            15.4 GB    disk1s5
   6:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.4 GB    disk1s5s1

I've tried to resize disk0s2 like this:

diskutil apfs resizecontainer disk0s2 300G ExFat SharedSwap1 0

And receive the error:

Aligning shrink delta to 60,999,999,488 bytes and targeting a new physical store size of 299,999,997,952 bytes
Determined the minimum size for the targeted physical store of this APFS Container to be 360,999,997,440 bytes
Error: -69521: Your APFS Container resize request is below the APFS-system-imposed minimal container size (perhaps caused by APFS Snapshot usage by Time Machine)

Upon checking snapshots:

diskutil ap listSnapshots /Volumes/Macintosh\ HD              
Snapshot for disk1s5s1 (1 found)
|
+-- DB4F6629-4C9B-41AC-A37F-B46CA4D1FA7B
    Name:        com.apple.os.update-E64B3CD15985B90FDC72FFBC9FFB352590E652026671C1695E4EA97D9050DD14
    XID:         3287758 (Will root to (boot from) this snapshot)
    Purgeable:   No
    NOTE:        This snapshot limits the minimum size of APFS Container disk1

Is it possible to resize and allocate more space, or should I just format and reinstall both operating systems again? If the latter is there a recommended process for my end result of Mac partition, Windows and shared exFat space?

bananakid · Answer 1 · 2022-09-18T14:45:15.580

According to error description (perhaps caused by APFS Snapshot usage by Time Machine) you may have Time Machine up and running that causes such behavior. To double-check if you've got those snapshots use tmutil listlocalsnapshots / in Terminal.

Basically you need to remove all Time Machine backups stores, disable all destinations, etc. You can re-associate your backups later. Detailed explanation about snapshots is in this answer and this article. Detailed instructions are provided in this help article by Apple. Remember that snapshots aren't exactly backups and are recreated every hour, so no harm deleting them as far as you keep your backup. Then you should be able to resize your APFS volume via Disk Utility or Terminal just as you attempted earlier.

If you want to delete local snapshots manually, turn off Time Machine temporarily. Here's extract from Apple's help article:

How local snapshots use storage space

You don't need to think about how much storage space local snapshots are using, because they don't use space needed for tasks like downloading files, copying files, or installing new software.

Your Mac counts the space used by snapshots as available storage. Even so, Time Machine stores snapshots only on disks that have plenty of free space, and it automatically deletes snapshots as they age or as space is needed for other things.

If you want to delete local snapshots manually, turn off Time Machine temporarily:

Open Time Machine preferences from the Time Machine menu in the menu bar. Or choose Apple (left-top) > System Preferences, then click Time Machine.

Deselect ”Back Up Automatically” or click the Off/On switch, depending on what you see in Time Machine preferences.

Wait a few minutes to allow the local snapshots to be deleted. Then turn on Time Machine again. It remembers your backup disks.

How often local snapshots are saved

Time Machine saves one snapshot of your startup disk approximately every hour, and keeps it for 24 hours. It keeps an additional snapshot of your last successful Time Machine backup until space is needed. And in macOS High Sierra or later, another snapshot is saved before installing any macOS update.

In case you decide to reinstall everything from scratch let me know, I will update the answer on that. But you should be fine with your initial plan once you turn off Time Machine stores temporarily.

score 0 · Answer 2 · answered Sep 18 '22 at 21:36

I would personally grow the APFS container by the 10 GB and put an external drive for the FAT common file store.

You can’t easily defragment APFS and it’s been out for several years, so whatever has prevented people from updating third party utilities is likely to continue.

macOS will run far better with undo snapshots and time machine backups with more space as opposed to less space. Also, the OS is a read only, sealed snapshot so any attempts to control them with Time Machine alone need to be lucky to succeed.

We would need you to post where your space on the Mac side is consumed to give more advice on what to move to an external to then try your shrink operation, technically your command is sound and will succeed once the system frees block allocations to accommodate the shrink.

Start with a system information post on the usage and consider a tool like Daisy Disk if the native space usage commands don’t get you an idea where your space has gone to prevent the shrink operation.

Resize Mac Partition after bootcamp, snapshot limitation

2 Answers2