Do I need to delete Time Machine snapshots?

Sometimes yes. Local TM snapshots can occupy the space you are trying to free, blocking the resize operation.

Is it safe to resize an APFS container?

Generally yes, but always back up first. Data loss is rare but possible if the operation is interrupted by power loss.

Mac Error 69854 — APFS Revert/Resize Operation Failed

Errordisk

Overview

Mac error 69854 occurs during APFS container operations like resizing, reverting snapshots, or volume group modifications when the operation cannot be completed.

Key Details

Error 69854 is an APFS-specific error indicating a container/volume operation failure
Common when trying to resize an APFS container or revert to a snapshot
Can occur during Boot Camp partition operations on APFS-formatted drives
APFS space sharing between volumes makes resizing more complex than traditional partitions
Time Machine snapshots may prevent container resize operations

Common Causes

APFS container cannot be resized due to data placement on disk
Time Machine local snapshots consuming space and blocking resize
Boot Camp Assistant unable to partition APFS container
Corrupted APFS container metadata
FileVault encryption in progress blocking volume operations

Steps

1Delete Time Machine local snapshots: tmutil listlocalsnapshotdates / then tmutil deletelocalsnapshots [date]
2Resize APFS container via Terminal: sudo diskutil apfs resizeContainer diskXsY SIZE
3For Boot Camp issues: delete all local TM snapshots first, then retry partition
4Run First Aid on the APFS container before attempting resize
5If FileVault is encrypting/decrypting, wait for it to complete before resizing