Member Avatar for petersons

My 500GB HDD have 5 partitions including a time backup drive. Few days back I created another partition of size 50GB for some purpose. Later I deleted that partition and tried resizing OS partition to take the space. But everytime I try to resize the OS disk, the disk utility fails to complete the action. It doesn't give any error message but the resizing is not completed by the DU.

Now my question is how could I resize my OS partition to take that space? Thanks!!!

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  • Latest Post Latest Post by tompatrick

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Short, practical explanation and steps to diagnose why Disk Utility won’t grab that freed 50 GB and how to fix it safely.

Disk Utility often fails silently when the startup volume is being changed while in use, or when the disk uses a storage layer Disk Utility can’t easily change in-place (CoreStorage/FileVault2 on older macOS, APFS container layouts on newer machines), when APFS/Time Machine snapshots are present, or when the partition map is nonstandard (hybrid MBR/Boot Camp). Booting from Recovery or another external environment is frequently needed to make the change because the boot volume can’t be modified while it’s active. (support.apple.com)

Quick diagnostics to run in Terminal (do these first; they won’t change anything):

diskutil list
diskutil coreStorage list     # look for CoreStorage (FileVault2-era)
diskutil apfs list           # look for APFS containers (newer macOS)

If you see a CoreStorage logical volume, get its LV UUID and run:

diskutil coreStorage resizeVolume <LVUUID> 0

If you see an APFS physical store, grow the container to fill the free space:

diskutil apfs resizeContainer <physicalStoreID> 0

The trailing 0 tells diskutil “grow to fill available space.” (manpagez.com)

If resizing still fails, check for snapshots (local Time Machine or APFS snapshots) and remove them first:

tmutil listlocalsnapshots /
diskutil apfs listSnapshots /
sudo tmutil deletelocalsnapshots YYYY-MM-DD-HHMMSS
sudo diskutil apfs deleteSnapshot / -uuid <snapshotUUID> -wait

Snapshots can block container resizing until removed. (keith.github.io)

Run First Aid (or the command-line verify/repair) from Recovery, and always have a current full backup before destructive steps:

diskutil verifyVolume /dev/disk0s2
diskutil repairVolume /dev/disk0s2

If the partition map is hybrid/BootCamp-related or badly fragmented, you may need to back up, remove the extra partition(s), recreate the desired layout, and restore — that’s often the safest route. ()

Note: ’ problem matches these causes; was right that a non-running (recovery/external) environment helps. If unsure at any step, keep a clone or Time Machine backup and post the exact diskutil list output before proceeding.

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Member Avatar for petersons

Thanks for reply. I have downloaded the software but its asking to create boot dvd?

Do I have to make the CD? Is it free?

Member Avatar for tompatrick

Hi again, you have to create a boot dvd since your mac has only 1 HDD. Note, software consider all partitions of the same hard drive as 1 single HDD. So, yes you have to burn the disk & work in bootable environment to resize OS X disk. Software is paid $29. Thanks!!!

Member Avatar for petersons

Thanks tom, I bought it and resized the startup disk easily. thanks for helping me out.

Member Avatar for InkHogNeato

Another great tool (just as an FYI) is DiskWarrier. It's gotten me out of more than a few jams!

Member Avatar for tompatrick

Disk Warrior is a tool that repair a corrupt Mac partition. It has nothing to do with resizing a Mac disk. Hope this adds good to your knowledge :-)

Edited by tompatrick
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