Time Machine Hiccups – What To Do When Time Machine Goes Wrong

Time Machine is a really wonderful backup system for personal use. It takes all the pain out of backing up and remembering to backup. As great as it is, Time Machine can give you a headache when it doesn’t work right. Here are some common Time Machine ailments, and what to do to fix them:

Stop the “Do you want Time Machine to Use this disk?” prompt:

If you use multiple external drives, then you understand the major annoyance this can be. So, here’s how you turn it off!

– Open Terminal
– If you have not set up Time Machine, type the following:

defaults write /Library/Preferences/com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool YES

– If you have set up Time Machine, type the following:

defaults write com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool YES

If you want the prompt back, re-enter the commands in Terminal but change YES to NO.

Changing the Time Machine backup interval:

By default, Time Machine is set to run a backup once per hour. If you want to change this, there are two ways:

1. If you are an advanced user:
– Navigate to: /System/Library/LaunchDaemons/
– Open com.apple.backupd-auto.plist in a Text Edit.
– Change the following key:


Note: The interval is set in seconds (3600 seconds = 1 hour). For best results, make sure you calculate this properly.

2. If you are a normal user:

– Download and Install Time Machine Scheduler by Stefan Klieme.

Past backups don’t appear in the time travel window:

Time Machine won’t see past backups if your computer’s name includes certain characters. While Apple doesn’t specify which characters, we can probably assume they mean characters such as ” ! @ # $ % & ^ { | } and ?. You can change your Mac’s computer name in System Preferences by clicking on the “Sharing” button.

Time machine stops backing up after 10GB:

Some external hard drives ship with a PC partition type, called Master Boot Record (MBR). Time Machine needs one of the Apple Partition Types. You will have to repartition your external drive to GUID if you have an Intel Mac or Apple Partition Map if you have an older PPC Mac.

To repartition:

– Run Disk Utility (It’s in the Utilities folder, inside the Applications folder).
– Choose the Partition tab.
– Click on “Options…”
– Choose GUID for Intel Macs, Apple Partition Map for PPC Macs.
– Click OK.
– Click Apply to erase the disk.

After you are done repartitioning, add the disk again to Time Machine and it should happily back up more than 10GB.

Note: Repartitioning will erase everything on your external drive. Make sure you’ve backed up anything important before you do this.

Time Machine is “Preparing…” for quite a long time:

In order for Time Machine to function properly, keep track of your files and the changes to those files, Time Machine needs to build an inventory or catalog of them. If something goes bonkers with that catalog file or Time Machine loses track of the changes to your files, it has to rebuild its inventory. When this happens, it will sit there, “Preparing…” for a few minutes. (Possibly more than a few if you’ve got a ton of files). This is normal – just let it run and when it’s finished, Time Machine will function properly.

Time machine doesn’t back up to Airport disks:

According to Apple, Time Machine doesn’t support this. Probably because no one would buy their Time Capsule if it did. You can get around this nonsense by using iTimeMachine by Xiotios Software.

“The backup volume could not be found”:

If your external drive has a “sleep” function where it spins down the drive after a certain amount of inactivity, it may not wake up for a Time Machine backup. If this is the case, disable the sleep mode on the drive. If you are unable to disable sleep, just eject the drive, unplug it and plug it back in. Then manually kick off a TIme Machine backup.

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