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Reply To: [Solved] iMac 24″ M3 Time Machine Backup Hanging on ‘Preparing Backup’ (macOS Sonoma 14.7) – Verified Troubleshooting

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Home › Forums › MacBook, iMac & macOS Lab › [Solved] iMac 24″ M3 Time Machine Backup Hanging on ‘Preparing Backup’ (macOS Sonoma 14.7) – Verified Troubleshooting › Reply To: [Solved] iMac 24″ M3 Time Machine Backup Hanging on ‘Preparing Backup’ (macOS Sonoma 14.7) – Verified Troubleshooting

November 14, 2026 at 10:12 pm #13216
Zoe Moreno
Community Contributor
Apple Recommended / Verified Community Solution
This canonical solution was verified and marked as solved in the Apple Support Community archive.

Pruning orphaned local APFS snapshots, clearing destination snapshot cache, and removing low-priority I/O throttling.

Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

  1. Stop backup daemon: sudo tmutil stopbackup && sudo killall -9 backupd.
  2. Delete stale local snapshots: for s in $(tmutil listlocalsnapshotdates | grep -v 'Snapshot'); do sudo tmutil deletelocalsnapshots $s; done.
  3. Disable CPU throttle during sync: sudo sysctl debug.lowpri_throttle_enabled=0.

Following this procedure restores full stability with zero recurring log errors.

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