OS X Mountain Lion: If your Time Machine backup disk runs out of space

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If your Time Machine backup disk runs out of space

When you first set up Time Machine, it performs an initial backup of your entire computer. During subsequent backups, Time Machine finds and saves only new items and items that have changed, so the backups become smaller. Also, as your backup disk fills up, Time Machine deletes older backups to make room for new ones. You may be able to use Time Machine for a long time before running out of space on your backup disk.

If you do run out of space, the best thing to do is connect a new backup disk. After you connect the new disk, open Time Machine preferences, and then select it as your Time Machine backup disk.

If you connect a larger disk and wish to preserve your existing backup history, you can copy the Backups.backupdb folder from the old disk to the new one. Use Finder, and not Terminal or any other application, to copy the Backups.backupdb folder. (The folder is large and it may take a long time to copy.)

To save space on your backup disk, you can back up fewer items. For example, if you keep your photos backed up with an online account, you may want to exclude them from Time Machine backups.

Last Modified: Sep 4, 2015
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