How to Reclaim Storage Space on a Time Capsule

Is your Time Capsule full? Would you like to free up some room for either newer backups of your data or to add another computer in your home? If so, here are some instructions on  this process.

[Note: You need to be comfortable using Terminal and issuing some basic Unix commands in order to free up storage space. You can really mess things up if you use Terminal and are not sure what you’re doing, so hire a consultant if you’re unsure.]

Time Machine uses different methods for storing data on local (USB or Firewire) hard drives versus the hard drive in a Time Capsule. On a Time Capsule hard drive, Time Machine stores your backup files in a special type of disk image known as a sparsebundle. You don’t need to know what a sparsebundle is, but it’s important to understand that it has important implications when it comes to freeing up space on a Time Capsule hard drive.

On a local hard drive, if you want to delete some of the backup data, you open Time Machine and select the date of a particular backup. Then, click on the Action menu icon, which looks like a gear in the Finder window, and select Delete Backup. Time Machine will proceed to delete the files in that particular backup and this will free up space on the local hard drive.

On a Time Capsule hard drive, when you follow this same procedure to delete the files in a particular backup, you don’t free up storage space on the Time Capsule since the sparsebundle disk image does not change in size. To reclaim the storage space you need to issue a command to shrink the sparsebundle disk image. Here are the steps:

  • Open the Terminal application and type cd /Volumes/
  • Select your Time Capsule hard drive and navigate into its subdirectories to find the correct .sparsebundle file. The sparsebundle file will have the general form of ComputerName MACaddress.sparsebundle. Write down the name of this file, as you’ll need it in a second.
  • Type the following command in Terminal: hdiutil compact SparsebundleName.sparsebundle
  • Now sit back and wait. Depending upon how many backups you deleted and how large your sparsebundle was when you started, this compacting could take anywhere from a few minutes to overnight.

When the compacting is complete you’ll see that you have more storage space available on your Time Capsule.

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