How to get Time Machine on a Mac to work

u587162 used Ask the Experts™
I've only recently started using Time Machine and have an external drive.  What is the correct way to get Time Machine to do a periodic backup when I want it to all happen in the background whilst I sleep and shut the lid of my mac book air?  Do I just plug in the USB cable or do I have to do something before I shut the screen?
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Plug in the external drive.

Open Disk Utility (found in /Applications/Utilities) and use it to completely erase the external drive and reformat it as Apple Extended Format (Journalled).

Go to Apple Menu > System Preferences > Time Machine

Check the button for "Show Time Machine in the Menubar".

Turn Time Machine On.

Click on Select Disk and select the external drive.

Time machine will then automatically do an incremental backup whenever the external drive is attached.
Doesn't the MacBook Air sleep when shut? In that case, it won't wake up to do TImeMachine.
If your MacBook Air supports "power nap" it should back up while asleep:
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Note that you have to enable Power Nap in the Energy Saver prefs.
noxchoIT Product Manager
Top Expert 2009
Here is a  video tutorial:
A lady explaining the usage of Power Nap:
Might I add an additional suggestion
By default TimeMachine runs every hour - I find this to be over-enthusiastic and prefer it only to run a few times a day.  As there is only an ON/OFF option within TimeMachine itself I use this FREE application to allow you to set an alternative interval for the backups
TimeMachine Editor -
If the user is only going to plug in the external drive when he puts the computer to sleep for the night, altering the backup interval is probably redundant. My understanding is that Time Machine will only back up once while the computer is asleep.
Plugging an external USB device in and out on a daily basis will cause significant wear & tear on the USB port over time.  I always recommend leaving the external drive plugged in as much as possible and only unplug when necessary.  I understand it is a portable laptop but if it is sitting at a work or home desk for several days at a time then I'd recommend leaving the external USB drive plugged in as much as possible.

The reason I suggested that you use the TimeMachine Editor program is because you can ensure that TimeMachine only runs at a certain time each day and not hourly even when it is plugged in.

@strung If you don't use TimeMachine Editor and you keep unplugging the USB drive, you will constantly get errors when the device is unplugged that TimeMachine cannot find or locate the backup device.  This is because if TimeMachine is enabled it will try and backup every hour by default.  It is completely impractical for the user to be enabling and disabling TimeMachine in the system preferences.

Finally, TimeMachine has its flaws in that it really works best when the external HD is permanently connected.  For example I am not aware of a method to configure it to run ONLY when the lid closes or the device goes to sleep.  You can also backup with TimeMachine over WiFi to a network storage device .. which might make more sense to investigate if the laptop is mobile and plugging in/out an external HD becomes tiresome.

There are other backup applications such as ChronoSync which are more configurable and flexible and can perform backups based on startup/shutdown and other events.


Will try this next week and revert, thanks.

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