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I've just replaced my existing MacBook Pro with a new MacBook Air. I've got 18 months of Time Machine backups from the old computer. I'd like to configure my new computer to use the old computer's Time Machine backups, so the new computer picks up where the old one left off. Is this possible? If so, how?

I didn't restore the new computer from a Time Machine backup because my old computer used more disk space than my new computer. There was a lot of cruft as well, so I decided to start from scratch on the new one. I'm slowly pulling off individual files and settings from a clone of the old computer's hard drive.

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  • So what do you mean by "use the old computer's Time Machine backups" if you don't mean restoring from it?
    – Daniel ♦
    Dec 3, 2011 at 4:15
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    The backups from my old computer use 1.1 TBs of a 1.5 TB drive. If I start backing up my new computer from scratch, the new backups will be limited to the remaining 0.4 TBs. If I tie the new computer to the old computer's backups, I get access to the old computer's files (which is what I want, since conceptually the two machines are the same) and Time Machine will delete old backups to free up space.
    – splattered bits
    Dec 6, 2011 at 19:55

9 Answers 9

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I found the following solution here:

sudo tmutil associatedisk -a "/Volumes/Macintosh HD" "/Volumes/Time Machine Disk/Backups.backupdb/John Doe's MacBook/Latest/Macintosh HD"
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By now, there seems to be a dedicated tmutil command:

sudo tmutil inheritbackup <path to previous time machine backups on mounted volume>

Example:

sudo tmutil inheritbackup /Volumes/Seagate\ Backup\ Plus\ Drive/Backups.backupdb/MacBook
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    This also works with the ".sparsebundle" file specified as the argument.
    – samkass
    Apr 19, 2015 at 23:03
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    Works perfectly! For reference, effective on macOS Serra, too.
    – Michael Ahlers
    Oct 6, 2016 at 14:31
  • @PascalVanHecke Does this work with Mavericks?
    – iwantmyphd
    May 19, 2017 at 17:05
  • I just got this error using .sparsebundle: sudo tmutil inheritbackup /Volumes/Data-2/Adam’s\ MacBook\ Pro.sparsebundle Error: Attaching disk image... /Volumes/Data-2/Adam’s MacBook Pro.sparsebundle: Attach failed: Failed to attach disk image. (error 35) Any ideas? I am on High Serra
    – Adam Moisa
    Sep 6, 2017 at 1:49
  • @AdamMoisa Make sure you unmount the sparsebundle first. You perform the inheritbackup operation with the sparsebundle unmounted, then mount it and perform the associatedisk operation.
    – Andreas Yankopolus
    Nov 15, 2017 at 2:36
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  1. Make sure the name of the new computer's hard drive is the same as the old computer's hard drive. Click once on the hard drive and hit enter to rename.

  2. Make sure the new computer's name is the same as the old computer's name. Open System Preferences, then Sharing. Enter the name in the Computer Name field. (This step may not be necessary, but it's what I did.)

  3. Plug-in the existing Time Machine drive. Open the Time Machine preferences and turn Time Machine on. Click Select Disk… and choose the Time Machine drive. After a few seconds, the backup will start. It will probably take awhile because OS X recognizes that you're backing up an entirely new disk, so backs up the entire disk. It might have to delete a few of your oldest backups, depending on how much space is left on the Time Machine drive.

After the first backup, you can safely change the name of the new computer and its hard drive.

Update: Using this technique, you won't be able to browse any backups from your previous computer with the Time Machine interface (although they are removed when Time Machine needs to free up space for new backups). The old backups are still visible and accessible from the Finder.

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    I don't get what are you trying to accomplish with all this renaming business. As far as I know Time Machine recognizes backup sources by UUID and not name of the hard drive. Did I missed something?
    – iskra
    Dec 6, 2011 at 18:49
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    It does use UUID, but also watches the name of the disk. If OS X detects the UUID of a disk changes, it falls back on the disc's name to pair a disk with a backu. The first backup after the UUID changes, it will do a full backup of the new disk (because it knows the disk is different), but as part of the history of the old disk.
    – splattered bits
    Dec 6, 2011 at 19:46
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There is also an extensive guide to troubleshooting Time Machine over on Apple OSX and Time Machine Tips (archive.org link because the original has gone away...) especically the following:

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I restored everything to a new machine and has this problem. I found a new folder on my backup disc indicating that Time Machine had tried to back up the new computer. I deleted it, and when I asked for a backup I was given the option of "inheriting" the old backups. When I accepted this option, everything was fine.

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If you want to back up to the same Time Machine disk that your old computer did, you can do that by plugging the external disk in and selecting it for Time Machine. If you don't restore from that backup, however, Time Machine will house both backups on the same volume, but you won't be able to pull files off of the drive from the other computer through the Time Machine interface. You can get to the other computer's backups by accessing the drive through /Volumes in the Finder.

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    This isn't what I want. I don't want to just use the same disk; I want to use the same backups.
    – splattered bits
    Dec 6, 2011 at 8:17
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Don't know if back then the Migration Assistant was less customizable...
I just did something similar and had the impression with the Migration Assistant I had quite some freedom what to take over or not to a new machine. I migrated from a MacBook Pro to a new iMac with the wish to keep both - my MacBook Pro and the new iMac - running in parallel and also with individual backups. As told I used the Migration Assistant and could then deselect all kind of stuff, also applications. Of course I didn't have the issue of lack of storage on the iMac as you with your move to a MacBook Air, but i would assume, you can deselect almost all data and application and keep only very little in the migration in order to keep some settings like the Time Machine without the need to migrate all. Once my migration was done, Time Machine started to do its process and told me, that there is already a Backup and whether I want to inherit the history of that Backup. For someone not wanting to fiddle around with renaming and commands probably the easiest way. The only issue I had then, was that the backup got stuck in the preparing process, but re-moving and adding - and confirming again the question to inherit the history of the existing backup - fixed the issue.

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You can restore a Time Machine backup via the Finder or using the terminal.

  • Open the Finder, open the Time Machine backup, open Backups.backupdb, and you see the old machine name.
  • Open that folder and you see a list of folders with dates, like 2023-10-05-164933. This backup is from 5 October 2023, at 16:49hrs.
  • Drag that folder to the restore location and it should work.
  • Source: https://mactakeawaydata.com/restore-files-from-time-machine-to-another-mac/

Using the terminal you can use rscync:

  • Open the Finder and find the right backup folder like shown above.
  • Open the Terminal and become root: sudo -i (you should be administrator to be able to do this)
  • Type: rsync -axv
    • Now drag the folder from the Finder into the Terminal, and you should see sometime like this:
    • rsync -axv /Volumes/backupdisk/Backups.backupdb/oldmachinename/2023-10-05-164933
    • Complete this with the destination folder:

Terminal command:

rsync -axv /Volumes/backupdisk/Backups.backupdb/oldmachinename/2023-10-05-164933 /Volumes/restoredisk/

If you need to shutdown the computer you can quit at any moment and simply repeat later on. Rsync will skip all files already copied.

In the end you might want to change the ownership from root to your own account.

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I am far from having knowledge about this stuff, but it seems to me one of the Apple Support people had me disconnect the power from the Airport Extreme and restart it. I just "cloned" my lap top pro from old to a new lap top and got grief from Time Machine. I shut everything down, and the next thing I see "Would you like to inherit from Airport", so I clicked "Inherit". Woola, I looked up at the screen and it's working.

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