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Restoring from a Time Machine back-up - puzzlement!

Hello - I've read here: https://support.apple.com/en-gb/HT203981


Yesterday, I decided to wipe the hard drive on my iMac and reinstall Catalina from my Time Machine back-up. When I had to choose WHICH back-up to install, I noticed something which I felt was rather odd. Instead of simply choosing a particular date/time of the back-up to use, I had a choice of which hard drive to select too! There were many more dates available on one of the disks than the other. I took a photograph of what I saw to show what I mean:-



Have you ever encountered such a thing before? HD and HD1 - as I’m sure you can see.


SHOULD it be like this? Is it a phenomenon of macOS Catalina perhaps?


I decided NOT to use my Time Machine back-up at all. I did erase my hard drive ……… and then did much ‘fiddling’ to get Catalina back up-and-running again on this machine. Everything seems to be working but I’m keeping my external hard drive in its original state for now - I’m NOT making any back-up for the time-being,


I’d really appreciate your thoughts on this. Thanks.


iMac 27" 5K, macOS 10.15

Posted on Oct 24, 2019 4:03 AM

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Question marked as Apple recommended

deggie's reply is correct.


Rather than concern yourself with the reason TM assigned unique names to the restore source, you really ought to start from the beginning. Describe the end result you are seeking.


The reason is important. You erased that Mac's startup disk, and now you want to restore a backup. Restoring a startup disk from a backup erases it first (TM tells you that) so erasing as a separate step wasn't necessary.


Furthermore, restoring the most recent backup recreates the exact same state that existed prior to erasing it. It gets complicated, because if you select "Macintosh HD" (or "HD 1") you are restoring its Local Snapshot. Time Machine tells you that too. That's a fine idea if your goal is to undo something you did subsequent to that backup's creation.


So, what you want to accomplish isn't clear to me.


Although a peculiarity of this site often results in similar or identical answers (often, existing replies don't appear until a new one is posted) unless I have something constructive to add I don't disturb a Discussion in which its OP is already receiving competent assistance. That's just me. I don't intend to impose that practice upon anyone, and in this particular case there's nothing to add to "you select the most recent backup," regardless of its name.


That's why I didn't reply. I'm replying now because you asked... but your question really needs more explanation: Why did you erase the startup disk?

Posted on Oct 27, 2019 12:08 PM

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33 replies

Oct 29, 2019 9:18 AM in response to HunterBD

The one thing I've gathered while seeing various posts on this type of problem is two folded:


  1. Fact: Catalina splits the hard drive into Mac HD and Mac HD - Data. The first is the system and not writeable - you have no access to it. The second contains everything else and you have read/write permissions. The only place to see this is in Disk Utility and those two should be listed.
  2. If there are two of either showing, it appears that it was a botched install and/or the drive was not erased before a "clean" install. Which would mean to use recovery and erase your drive completely and reinstall from Apple (rather than TM). You would have to use other means (setup assistant or drag 'n drop) to get your files moved over.

Oct 29, 2019 10:28 AM in response to babowa

Thank you for your comments, 'babowa.


I have now obtained an enclosure for the 1TB hard drive I purchased last winter to install in my old iMac. I have called this new external hard drive 'My Back-up!'. Incidentally, that was the machine which I attempted to repair by heating the chip on the graphics card with a gas blow-torch - and failed! 😉


I replaced it with another (second-hand) iMac which has an SSD fitted and which now has a clean installation of OS X El Capitan. I have now 'tested' 'My Back-up!' on that computer. I carried out a Time Machine back-up without difficulty. I then shut down my machine and then restarted in Recovery Mode. Here's the proof!



I then moved forward to see if I had just one HD from which to recover - and I did! 😊



Satisfied that all was working well, I restarted my old iMac and ejected the external hard drive. I then connected 'My Back-up!' to my new iMac as had been suggested by John Galt. Here's proof again:-



I restarted my new machine in Recovery Mode and looked to see what was on offer - was it just HD ......... or HD and HD1?

You can see for yourself:-


Out of interest, because someone here on ASC said it would be no problem, I decided to proceed as if to restore from the back-up. This is the message I was shown:-



That was not unexpected by me!


Satisfied that all is now working properly, I restarted my iMac and am now writing this message upon it! 😎


My WD My Book 2TB external drive must hold the secret as to why I was earlier offered the choice of HD and HD1 disks from which to restore. I'm still hoping that someone can suggest who - or what - may have tampered with that drive.


Can anyone suggest a means of scanning the drive for malware? I don't really want to load any anti-virus software onto either of my iMacs! 🤔


Thanks for listening!


David.





Oct 29, 2019 10:49 AM in response to HunterBD

You would have had to look before erasing and reinstalling.

I’ve only seen this on external drives, but if the drive gets “lost”, the OS might mount it again suffixing with a 1 since there is already a mount pour by that name.


My guess here is that happened with your startup drive (which I really can’t imagine). Time Machine then backed up both mount points.

Oct 29, 2019 11:32 AM in response to HunterBD

This is going to be my last comment here because it is delving into two things I do not use: TM (so I do not know how it works) and WD external drives, especially if they were not erased and formatted before use and therefore still have unnecessary WD software on them.


Your DU screenshot shows the two correct entries for your internal, so that is good. I have no idea what is happening on your external.

Oct 29, 2019 4:39 PM in response to HunterBD

Hi. When I updated to Catalina I had the same situation.

As far as I can understand, it has to do with Apple's new APFS file structure. While it looks like there are two volumes there, apparently it's really one and cannot be used as separate storage. Shortly after Catalina dropped Adobe advised Photoshop users not to upgrade to Catalina as there are unresolved issues. Functioning Pshop is vital to my work, so using a SuperDuper backup I restored my original content running macOS Mojave BUT I still have the two disks on my desktop.

My start up disk is Macintosh HD, but other contributors to this forum have recommended using Macintosh HD Data as your boot drive. My 2018 iMac is working okay though. I don't know if this helps. Good luck.


Oct 29, 2019 4:39 PM in response to babowa

babowa wrote:

This is going to be my last comment here because it is delving into two things I do not use: TM (so I do not know how it works) and WD external drives, especially if they were not erased and formatted before use and therefore still have unnecessary WD software on them.

I wonder if you've hit upon a possible reason - the WD hard drive possibly having some of WD's software still installed. 🤔

I've been using the drive for some years and cannot remember whether or not I erased same. The 'My Book' product was, IIRC, supposed to be delivered ready for use by a Mac owner.

Your DU screenshot shows the two correct entries for your internal, so that is good. I have no idea what is happening on your external.

I'm now using a new external hard drive and don't appear to be having any problems at all.


Thanks for providing your views, 'babowa'. 🙂

Question marked as Helpful

Oct 29, 2019 5:07 PM in response to HunterBD

An external does not need anything installed to function. So, it is good practice to erase them and use DU to format them. That way you know what is on it. So I have been doing that for years - even with drives from OWC which I prefer since their external enclosures and the chip used for the connection are far better than WD's stuff.

Oct 30, 2019 12:51 AM in response to babowa

babowa wrote:

An external does not need anything installed to function. So, it is good practice to erase them and use DU to format them. That way you know what is on it.


I completely understand that. Thank you.


So I have been doing that for years - even with drives from OWC which I prefer since their external enclosures and the chip used for the connection are far better than WD's stuff.


Is THIS the OCW to which you refer? https://www.owcdigital.com


I have no knowledge of, nor experience with, their products. I've always thought that Western Digital made good products but I'm simply a home user. Are you in some way better qualified to make the judgement that "the chip used for the connection are far better"? I was unaware that there is ANY "chip" involved! 😳

Oct 30, 2019 5:50 AM in response to HunterBD

Hi Hunter, the enclosure contains a chipset so the drive can communicate with the computer. A WD bare drive is fine but the quality of the chip they use in their enclosures is the issue she refers to. So if you were to purchase a WD bare drive and "roll your own" with an OWC enclosure, it should be fine.


The site you link to appears to be OWC but I've always used this link:

https://www.macsales.com

Maybe they just migrated to a new site.


Glad to see you got your TM issue sorted.


Restoring from a Time Machine back-up - puzzlement!

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