I don't have a definite answer yet either, but I'm basing my approach on bad content/permissions in the
.MobileBackups subtree. Since these files store incremental backups in-between true Time Machine backups, I'm somewhat comfortable removing them and "starting fresh".
Viewing the logs:
Missing from the question is how to view the Time Machine logs. I installed a script in my
/usr/local/bin directory, based on the answer here. However, a more straightforward command is simply:
log stream --style syslog --info --predicate 'processImagePath contains "backupd" and subsystem beginswith "com.apple.TimeMachine"'
Investigating Logged Errors
Inspecting the directories, there didn't seem to be much "off" about them (as @RamsayCons points out in his answer). Since I didn't care much about the most recent mobile backup, I decided to simply remove it:
sudo rm -rf /.MobileBackups/Computer/2016-12-16-112458
A few notes about this command:
- Remember that with
sudo comes great power. Please be sure you understand exactly what you are doing before continuing.
rm -rf can cause great pain and anguish, so be sure that you are confident in what you are doing and have an exact directory specified.
- use the command
ls -la /.MobileBackups/Computer/ to list the contents of your existing Mobile Backups, so you can specify the correct
I am still waiting to see if this will resolve my problem, but so far I am seeing a new set of messages in the logs.
A few differences in my problem vs. that described:
- I am backing up to a locally mounted drive, however, the problem seems rooted in the files stored in the
/.MobileBackups/ directory, and not related to "where" the TimeMachine Backup disk is located
- My errors include a message that
volume Macintosh HD (/) is now in an emergency freespace condition, and
low disk space thinning needed for volume Macintosh HD (/) with 7.7 <= 10.0 pct free space, despite having
>40GB out of
- My Backup never "failed", but sat in the "Preparing backup ..." status in System Preferences for over 18 hours.
My Time Machine Backup eventually completed during the next scheduled hourly run... Hooray!