Restore Mac OS X

How to recover a Mac from a Time Machine backup is a question that non of our readers want to ask, but occasionally have to. Sometimes the proverbial dirt just hits the fan.

All this assumes, of course, that you have backed up your Mac using Time Machine in the first place? You can't restore a Mac from a Time Machine backup if you don't have Time Machine set up in the first place. You have got Time Machine set up, haven't you? Just in case here's a quick primer.

Read Complete Guide to Time Machine

Creating a backup using Time Machine

Time Machine was designed by Apple to work with a spare USB drive. Setting it up couldn't be easier. Attach a new external USB hard drive and click Use As Backup Disk in the dialog window that says “Do you want to use this as a Time Machine drive?”

The USB drive will be wiped so make sure it doesn't contain any files you want to keep. And although you can move files to and from the attached drive using Finder, we advise you to leave it alone and only use it as a Time Machine backup.

Configuring a Time Machine backup with a second hard drive is simple. The greatest effort it takes is purchasing the drive and plugging it in. But using an external drive won’t protect you from a cataclysmic event – a massive power surge, fire or flood

Read more: How to set up a Time Capsule

Do you really need to reinstall Mac OS X?

First of all check if you really do need to re-install the whole drive. There are three things you should do before

1. Run Mac OS X Disk Utility from Recovery Mode

On a Mac running Mountain Lion, you can run Disk Utility by booting into OS X Recovery Mode.

Restart the Mac while holding down the Command and R keys.

You should boot into a screen headlined OS X Utilities.Click on Disk Utility and choose your Mac’s built-in hard drive in the left column Click Verify Disk, and then wait while Disk Utility does its thing. If there are any problems click Repair Disk.

Read more: Troubleshooting Disk repair

2. Run Mac OS X Safe Boot

Shut the Mac down, and start it up while holding down Shift. Safe Boot takes a while to start. If it does then you may be able to fix or repair Mac OS X. Try removing start-up items. Open System Preferences > Users & Groups choose you account, open Login Items and click the Remove '-' button to deselect options.

Read more: Troubleshooting Mac OS X startup problems

3. Run Mac OS X 'fsck'

This one's kind of geeky and fun. Shut the Mac off, and start it up again while holding Command and S. You’re launching Single User Mode. You can release the keys when the intimidating black screen with messages in white text appears.

Wait until the command-line prompt appears, when all the text is done scrolling past. Then, you’ll type fsck -fy and hit Return. And wait. Possibly for several long minutes.

Ideally, you’d eventually get to the “…appears to be OK” message, type reboot, and find that your Mac now starts up perfectly. Julian’s Mac had other ideas.

Read more: Steps to take when your Mac won't start up

Restore Mac OS X from Time Machine

Okay, so nothing has worked. You can use it to reinstall Mountain Lion, too. Boot into Recovery mode (hold down Command + R), and then click "Restore from a Time Machine backup" and follow the on-screen prompts.

If the restore doesn't work, you should reinstall Mac OS X completely. Boot into Recovery Mode (hold down Command + R during startup and choose "Reinstall OS X".

Follow the on screen prompts as usual until you get to the The "Do You Already Own a Mac?" window. This be used to open a program called Migration Assistant during install. Use this to restore all your files from your back. Choose the "From Time Machine backup" and click Next.

Mac OS X will be installed and the files from Time Machine will be placed back in their right order. This is a fresh installation of Mac OS X but with all your file and account information restored.

Migration Assistant is capable of restoring the following information:

  • Users
  • Networks and other settings
  • The Applications folder
  • Files and folders on “startup drive’s name”

You can choose all the areas (a complete reinstall) or just the parts you want.

Time Capsule

Renstall Mac OS X with Time Machine without the internet

Reinstalling OS X 10.8 via Recovery HD requires an Internet connection, as the installer has to both download OS X software and verify your computer’s eligibility. You can create a bootable Mountain Lion install drive . To do this, you’ll need a copy of the Install Mac OS X utility from the Mac App Store. Oh, yes and you'll need to have a working Mac so if yours is currently out of order you'll need to find a friend.

One complication here is that the Install OS X utility is moved to the Trash as part of an update/install to Lion. If you plan to use it again, save the application before it gets deleted. If this advice is coming too late, you can redownload a copy from the Mac App Store (by holding down the Option key when selecting the Purchases tab).

Read this: Mac troubleshooting: Be prepared for hard-drive failure

Restore Mac OS X: Further reading

See: Master Time Machine on the Mac

See: Apple Time Capsule 3TB review

See: Back up, wipe and restore your iPad