Old Time Machine, different computer

[Xairbusdriver]

There are lots of files on my external Time Machine backup. A couple I could really use tomorrow. However, from what I understand, if you select a drive with a TM backup on it, you will have a choice to "Reuse" the backup or "Create a New" backup.

I think the old computer can use the old backup again, even if you select "Reuse" because the new backup supposedly gets added to the old one (which will be a full backup since the two machines will hardly be the same).

I'm positive that if "Create a New" backup is used, the old backup will no longer be available to any computer. But I don't understand exactly why. <Here is my unofficial source.>

Yet in <this post> from Pondini, there is nothing said about not being able to access the old backup. He even claims none of the old data will be erased as will happen with "Create a New" selection.

[krissel]

From those links, I read it that if you are going to connect a new computer with a different MAC address, the previous backups would still be readable by the old computer only if you create a new backup for the new computer.  TM uses the MAC address of each computer to differentiate which backup can be used by which computer.

If you reuse the old backup for a new computer, it will now be associated with the new computer and the old computer will not be allowed to use it.  I gather from your post that you want to use the TM drive to backup both computers?  If not, please explain your intentions...



Partitioning in the future would solve this problem.  

[Xairbusdriver]

Sorry for the confusion, mostly thinking while typing (and both activities are pretty slow for me! )

Your are correct about the MAC address part. That makes sense in that computer "names" can be easily changed which could confuse any back up app. I did not realize this "feature" until reading those posts. In my humble opinion, it is a severe drawback for TM. While the majority of people replace one machine with a new one, I need access to the backups while my iMac is in the shop. But I cannot use another computer to see that TM backup without jeopardizing the use of them when the iMac is returned. Looks like a good place for a password and a method of bypassing the MAC address scheme, at least for reading the files.

I may have to investigate extracting individual files from the SuperDuper backups, however, the machine first indicated a problem while doing a SD backup (had to Force Quit SD! ). I will have to verify that the last backup is still there! Certainly no time for that today. Spent too much time upgrading Judy's MBP to the latest Garageband, downloading the LAME code for MP3 saving and re-editing 15 files from the server. Oh well...