Open the System Preferences app, select Time Machine, click its Options button and then click the plus-sign button.
Time Machine also doesn't state upfront how big the resulting backup set will be-unless it exceeds the size of your backup disk, at which point it will leave it to you to decide what to exclude.īefore you get into those weeds, however, first try finding the biggest files on the hard drive, as outlined here in March: Open a Finder window, click 'All My Files' in its left-hand sidebar, go to the View menu's 'Arrange By' item and choose 'Size,' and the largest items will top the list.ĭelete anything you don't need, and you'll not only have a trimmer backup set but a roomier hard drive.īut if that doesn't work, it's time to start excluding items from backup that you can recreate somewhat easily later on. Before everybody says 'well, duh, have it back up less stuff,' remember that filing down a backup set to fit on a given disk isn't so obvious in Apple's Time Machine software.īy default, this OS X feature backs up not just everything in your account on a Mac but everything on its hard drive.
My Mac keeps telling me that Time Machine could not complete the backup because the backup disk is out of space.
