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I'm trying to add a new partition to my Macbook, in order to dual boot with Linux. I have a 250GB drive, with 70GB free. However when I try to use Disk Utility it says "This volume can not be split because the resulting volumes would be too small."

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This answer tells someone having the same problem their drive is simply too small. Can I really not create a 70GB partition? What is the smallest size I would be able to create?

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While the Disk Utility application is move convenient than using the diskutil command, often the Disk Utility does not provide sufficient support for non-Apple related tasks. Adding Linux definitely falls into this category. The amount you can shrink a APFS container can found by using the diskutil command. For example, I have a APFS container on my external drive. Below is the partial output from from the command diskutil list. This shows the partitions on my external HDD.

/dev/disk3 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *400.1 GB   disk3
   1:                        EFI EFI                     209.7 MB   disk3s1
   2:         Microsoft Reserved                         16.8 MB    disk3s2
   3:       Microsoft Basic Data BOOTCAMP                125.7 GB   disk3s3
   4:       Microsoft Basic Data WINSTALL                11.5 GB    disk3s4
   5:           Windows Recovery                         629.1 MB   disk3s5
   6:                 Apple_APFS Container disk4         200.0 GB   disk3s6
   7:                  Apple_HFS BU                      61.3 GB    disk3s7
   8:                  Apple_HFS Macintosh HD via rEFInd 200.0 MB   disk3s8
   9:                  Apple_HFS Preboot                 200.0 MB   disk3s9
  10:       Microsoft Basic Data BOTTOM                  57.7 MB    disk3s10

Since the APFS container has the identifier disk3s6, I can use the command shown below to determine how much the APFS container can be resized.

 diskutil apfs resizecontainer disk3s6 limits

The resulting output is shown below.

Resize limits for APFS Physical Store partition disk3s6:
  Current Physical Store partition size on map:   200.0 GB (200000000000 Bytes)
  Minimum (constrained by files/snapshots):       76.7 GB (76683403264 Bytes)
  Recommended minimum (if used with macOS):       87.4 GB (87420821504 Bytes)
  Maximum (constrained by partition map space):   200.0 GB (200000000000 Bytes)

This output shows the minimum size is 76.7 GB. The size of the smallest partition you could created after the APFS container would be hard to determine exactly. Anything reasonably small would be accepted. For example, the command below would create new empty partition of approximately 100 MB in size.

diskutil apfs resizecontainer disk3s6 199.9G %noformat% none 0
  • Brilliant - thank you. The current output says "Minimum (constrained by files/snapshots): 250.8 GB (250790436864 Bytes)". Given there aren't 250GB of files on there, could this be caused potentially by Timemachine local snapshots (something a colleague said in passing) ? – matt freake Nov 18 '18 at 16:04
  • I suppose you could enter the command tmutil listlocalsnapshotdates / to get a list of snapshots. Next, you could enter the command tmutil deletelocalsnapshots YYYY-MM-DD-HHMMSS to remove a particular snapshot and see if you regain some space. I should warn you that I do not have much experience with Time Machine. I posted these commands after reading the instructions provided by entering the command man tmutil. – David Anderson Nov 18 '18 at 17:25
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Disk Utility will not allow a partition smaller than 10% of the disk size, so creating a 70 GB partition shouldn't be a problem for you. Try deleting all local Time Machine snapshots:

 tmutil thinlocalsnapshots /

If that doesn't work either, I'd recommend using a Live System such as Knoppix.

  • A ~28% partition should be fine with Disk Utility then. Can you expand your answer with more details on why Disk Utility isn't able to perform this partition? – grg Nov 18 '18 at 12:11

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