First, you should purchase an external hard drive to back up your data to. ResNet recommends the Western Digital brand of external hard disks, and they are available for purchase at the Shaheen Bookstore (and may be charged to your student account),, and Best Buy.

    When you connect your external hard drive for the first time, Apple's Time Machine software will ask if you would like to use the external drive as a back up drive (unless you've already specified a backup disk). Click "Use as a Backup Disk" to confirm you want to use the disk for Time Machine backups. Time Machine preferences will then open with this disk selected as your backup and Time machine will be turned on.

    Depending on the amount of data you have, your first back up may take a few hours to complete. You should not interrupt the initial backup. You can continue to use your Mac while Time Machine backs up. You can tell that your computer is actively backing up data by the looking at the icon of a clock in the upper right corner of your Mac's screen - if the arrow surrounding the clock is rotating, the data is backing up, if the arrow is still, there is no backup taking place.

    Once the initial backup is completed, Time Machine performs subsequent hourly backups of only the files that have changed on your Mac since the last back up (as long as your backup disk is connected). You can back up your data at any time by clicking on the icon of a clock in the upper right corner of your Mac's screen and selecting the Back Up Now option.

    Time Machine keeps hourly backups for the past 24 hours, daily backups for the past month, and weekly backups until your backup drive is full. It will then discard old backups and continue to back up your current system.

    For information from Apple on Time Machine, please visit

Last Modified July 29, 2019