問題
n個月前MacOS升級到High Sierra 10.13之後Time Capsule（時間機器 !H_P?）就沒備份成功過。
第一次備份總是會等了很久之後顯示失敗。
翻查log
在Terminal輸入以下可以查看Time Capsule的記錄
clear; printf '\e[3J' && log show --predicate 'subsystem == "com.apple.TimeMachine"' --info --last 24h | grep -F 'eMac' | grep -Fv 'etat' | awk -F']' '{print substr($0,1,19), $NF}'結果顯示
2018-09-13 22:49:47 Maximum urgency thinning requested!
2018-09-13 22:49:47 Completed thinning of snapshots on disk '/' in 0.0 seconds - current free space: 3.17 GB（3,167,989,760 字節）, target free space: 12.87 GB（12,872,359,936 字節）, initial free space: 3.17 GB（3,167,989,760 字節）, urgency: 4, remaining snapshots: (
2018-09-13 22:49:50 Starting age based thinning of Time Machine local snapshots on disk '/'
2018-09-13 22:49:50 Starting space based thinning of purgeable local snapshots on disk '/' - current free space: 3.06 GB（3,062,710,272 字節）, target free space: 12.77 GB（12,767,080,448 字節）, initial free space: 3.06 GB（3,062,710,272 字節）, urgency: 3
2018-09-13 22:49:50 Completed thinning of snapshots on disk '/' in 0.0 seconds - current free space: 3.06 GB（3,062,710,272 字節）, target free space: 12.77 GB（12,767,080,448 字節）, initial free space: 3.06 GB（3,062,710,272 字節）, urgency: 3, remaining snapshots: (
2018-09-13 22:50:32 Checking for runtime corruption on /dev/disk2s2
2018-09-13 22:50:48 Disk image /Volumes/Data/MBP.sparsebundle mounted at: /Volumes/時間機器備份
2018-09-13 22:50:51 Backing up to /dev/disk2s2: /Volumes/時間機器備份/Backups.backupdb
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.SnapshotVolumeFSEventStoreUUID' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.SnapshotVolumeLastFSEventID' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.SnapshotVolumeUUID' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.PreviousSnapshotVolumeUUID' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.PreviousSnapshotVolumeName' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.VolumeBytesUsed' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.VolumeIsCaseSensitive' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.fstypename' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to remove attribute 'com.apple.backupd.VolumeIsEncrypted' from 'file:///', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to write unlock record UUIDs as extended attribute for disk '/', error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"
2018-09-13 22:50:51 Failed to create APFS snapshot with name 'com.apple.TimeMachine.2018-09-13-225051' on volume '/', error: Error Domain=NSPOSIXErrorDomain Code=28 "No space left on device"
2018-09-13 22:50:51 Failed to create local snapshots
2018-09-13 22:50:51 Failed to create or mount stable snapshot.
2018-09-13 22:50:55 Starting age based thinning of Time Machine local snapshots on disk '/'
2018-09-13 22:50:55 Starting space based thinning of purgeable local snapshots on disk '/' - current free space: 4.33 GB（4,330,475,520 字節）, target free space: 14.82 GB（14,817,637,171 字節）, initial free space: 4.33 GB（4,330,475,520 字節）, urgency: 1
2018-09-13 22:50:55 Completed thinning of snapshots on disk '/' in 0.0 seconds - current free space: 4.33 GB（4,330,475,520 字節）, target free space: 14.82 GB（14,817,637,171 字節）, initial free space: 4.33 GB（4,330,475,520 字節）, urgency: 1, remaining snapshots: (
2018-09-13 22:50:57 Starting age based thinning of Time Machine local snapshots on disk '/'
2018-09-13 22:50:57 Starting space based thinning of purgeable local snapshots on disk '/' - current free space: 4.28 GB（4,279,517,184 字節）, target free space: 14.67 GB（14,674,322,227 字節）, initial free space: 4.28 GB（4,279,517,184 字節）, urgency: 2
2018-09-13 22:50:57 Completed thinning of snapshots on disk '/' in 0.0 seconds - current free space: 4.28 GB（4,279,517,184 字節）, target free space: 14.67 GB（14,674,322,227 字節）, initial free space: 4.28 GB（4,279,517,184 字節）, urgency: 2, remaining snapshots: (
2018-09-13 22:50:59 Backup failed with error 50: 50
2018-09-13 22:51:02 Starting age based thinning of Time Machine local snapshots on disk '/'
2018-09-13 22:51:02 Starting space based thinning of purgeable local snapshots on disk '/' - current free space: 4.36 GB（4,358,701,056 字節）, target free space: 12.87 GB（12,871,098,368 字節）, initial free space: 4.36 GB（4,358,701,056 字節）, urgency: 3
2018-09-13 22:51:02 Completed thinning of snapshots on disk '/' in 0.0 seconds - current free space: 4.36 GB（4,358,701,056 字節）, target free space: 12.87 GB（12,871,098,368 字節）, initial free space: 4.36 GB（4,358,701,056 字節）, urgency: 3, remaining snapshots: (
2018-09-13 22:51:27 Failed to eject volume /Volumes/時間機器備份 (FSVolumeRefNum: -157; status: -47; dissenting pid: 0)
2018-09-13 22:51:27 Failed to eject Time Machine disk image: /Volumes/Data/MBP.sparsebundle看來是權限問題了
解決辦法
想不到居然是Spotlight的問題，那就先關掉
sudo mdutil -a -i off
備份成功之後再重啓Spotlight
sudo mdutil -a -i on
參考
https://discussions.apple.com/thread/8339983
https://apple.stackexchange.com/questions/304661/time-machine-failing-to-complete-backup