I recently purchased a 1TB solid state hard drive Samsung Electronics 840 EVO-Series 1TB 2.5-Inch SATA III Single Unit Version Internal Solid State Drive MZ-7TE1T0BW.

I hope I won't need to manually reinstall the OS X and all the applications and copying back hundreds of GBs of personal data.

How do I replace hard drive without reinstalling the whole system?


This can be done with Time Machine. NOTE this will not make an exact bit-for-bit copy of your current harddrive, but will copy over all users' files, settings, applications, etc. (including /usr/local), as well as the operating system files themselves.

  • Time Machine does not backup cache directories, files that have been moved to the trash, etc. I have also found it does not backup the saved state of open applications nor Office product keys.

These steps are broadly from: https://www.imore.com/how-back-up-mac-time-machine.

  1. Connect your backup harddrive and make a current Time Machine backup by going to System Preferences -> Time Machine -> 'Show Time Machine in menu bar'. Then go to the menu bar icon and select 'Back Up Now'.

    • You should be backing up already (right?!?), so this should not take long.
    • If you have not made a backup already, enable Time Machine and then start the backup.
  2. Once the back up is complete, swap out your internal harddrive for the new one (following all safety instructions).

  3. Power on your computer and hold the Command and R keys to enter the recovery partition (this may take a few minutes).

  4. Select 'Disk Utilities' and ensure that the volume on your new harddrive is formatted as Mac OS Extended (Journaled).

    • If it is not, reformat it. This will delete all files on the new harddrive, but there should be nothing on your new harddrive so this should not be a probelm.
  5. Now quit 'Disk Utilities' to go back to the list of utilities.

  6. Select 'Restore from Time Machine Backup' from the Mac OS Utilities and click Continue.

  7. Select your Time Machine back-up source and click Continue.

  8. Select your latest back up and click Continue.

  9. Select your new hard drive as the Destination.

  10. This will restore over all backed up files to your new harddrive.

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  • Thanks, I've been looking at how to use time machine for this. – Andy Jun 23 '17 at 19:03

Have you considered cloning your current hard drive? With a utility like Carbon Copy Cloner (which you can use for free for 30 days, I think), and an external interface for your new hard drive (USB, Firewire, etc.), you can clone--i.e. make a bit-for-bit copy of your operating system and installed programs--the drive that's currently in your computer. Then, when you install the new hard drive, the computer should see it as the boot disk and everything should pick up exactly where you left off--just with a lot more storage.

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  • This is the easiest method in my opinion, assuming there is nothing wrong with your original system. The only caveat is that you need to have both drives connected (using an external drive connection), aside from that though it is a one step cloning of your hard drive to the new drive. – Mr Rabbit May 8 '14 at 16:44
  • That would be my preferred way too, and how I have done it in the past. You do need an external case for your new drive but those can be had cheaply. then just use SuperDuper or Carbon Copy Cloner and you are good to go. No need to install or reinstall the o/s – Steve Chambers May 8 '14 at 20:17
  • Thanks for this excellent no-nonsense answer. – qazwsx May 10 '14 at 5:24

The simplest method to install things is as follows:

  1. Connect the new drive to a USB to SATA adapter
  2. Partition and format the "external" drive using Disk Utility
  3. Download the OS X installer you want and install the OS on to the "external"
  4. When you boot to the external, let migration assistant copy everything to the "external"

Test that the "external" works properly, then and only then, make a final backup of the internal drive and swap the hardware.

The benefit of this method is not only that you keep your system unbroken while you test the OS and migration, you can know if you have a working drive and OS without needing to do any "wrench work".

You could use Disk Utility to simply clone the existing drive onto the SSD, but I prefer a clean install to let the OS place the OS files in the proper place and who knows what errors have crept into the existing system over time. Migration is really solid (it wasn't as robust 5 years or more back, and people rightly wanted to clone a working system more regularly then.) You could also use SuperDuper or Carbon Copy Cloner to do the duplication, but again - I really prefer a piecemeal, reinstall as it works best for me time and time again.

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  • Could you please clarify how to "download OS X installer ... and install ..."? – qazwsx May 7 '14 at 20:01
  • @user6076 You would download it from store.apple.com or the App Store unless you were running an OS older than 10.6 - probably best to just ask that specific question as a new post. – bmike May 7 '14 at 20:05
  • I need to purchase a new instance of OS X? I'm surprised. Can't I replicate the content on the current hard drive on the new SSD? – qazwsx May 7 '14 at 20:16
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    You are entitled to the OS that came with your Mac. If you purchased any upgrades, you can reinstall them for free. Furthermore, Mavericks is a free upgrade, so as long as you have 10.6 - you are eligible for a free upgrade. You also can clone the existing OS using Disk Utility. What makes you think you need to pay? – bmike May 7 '14 at 20:24
  • store.apple.com does not seem to give any option to "download OS X installer" etc. I don't have the installation CD. I only have the Macbook Pro with a working OS X 10.9.2. I believe before the upgrade it was 10.6.8. – qazwsx May 7 '14 at 20:38

You need to download the Mavericks Installer, then create a USB Install.

Since you already have Mavericks installed, you need to use following simple process.

Open Apple Store. Go to Purchase Tab


It will show you Mavericks Download...

It will ask you to confirm since you already have Mavericks.


Once downloaded to NOT run the Installer.

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