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Boot Mojave SSD from Catalina MBP?

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Bman70

macrumors newbie
Original poster
I just bought a new MacBook Pro, which I intended to downgrade to Mojave. However, clearly it can't since it shipped with Catalina. So, I thought of making a clone of my old MacBook Air hard drive which is Mojave, just to boot from when I need some older apps.

Is this as simple and straightforward as making a clone of the Air, then booting the MBP from it? While searching I've come across bits of gossip saying Catalina doesn't recognize Sandisk Extreme SSD as bootable, or has a different mode of creating volumes, etc., leading me to think there might be complications. Is SSD brand / type an issue, etc. So just thought I'd ask before starting such a project. Thanks for any pointers.
 
If the new MBP shipped with Catalina I don’t think it can boot Mojave at all... period. I’m pretty sure that Catalina is the lowest MacOS that that MBP can ever boot. It’s restricted in the firmware. You can only move forward with OS upgrades. It can’t go backwards to an OS that’s older than the machine itself.
 
Bman70 said:
I just bought a new MacBook Pro, which I intended to downgrade to Mojave. However, clearly it can't since it shipped with Catalina. So, I thought of making a clone of my old MacBook Air hard drive which is Mojave, just to boot from when I need some older apps.

Is this as simple and straightforward as making a clone of the Air, then booting the MBP from it? While searching I've come across bits of gossip saying Catalina doesn't recognize Sandisk Extreme SSD as bootable, or has a different mode of creating volumes, etc., leading me to think there might be complications. Is SSD brand / type an issue, etc. So just thought I'd ask before starting such a project. Thanks for any pointers.
Click to expand...
If your “new MBP” is a 2020 M1 MBP then Mojave will not work. If it is intel, then maybe. We would need to know the year of manufacture/release.
 
CoastalOR said:
If your “new MBP” is a 2020 M1 MBP then Mojave will not work. If it is intel, then maybe. We would need to know the year of manufacture/release.
Click to expand...

Oh right... it's a late (Nov?) 2019 6-core Intel Core i7. So not THAT new.. but still too new for Mojave from what I'm hearing. Apple customer service said MacBooks can never run anything older than what they shipped with.
 
Find your Mac on the list here.

All Apple MacBook Pro Specs (2006-Current): EveryMac.com

Tech specs for all Apple MacBook Pro from 2006 to the latest. Dates sold, processor type, memory info, storage details, configuration options, model identifiers and more.
everymac.com everymac.com

Scroll down to the bottom of the specs and it will show the oldest version of MacOS that it supports (ie: the original version that was installed)
 
If it shipped from Apple with Catalina (I reckon it did), then you CANNOT BOOT Mojave on it.

You could run Mojave using a "virtual machine" (created with Parallels or VMWare Fusion).
Other than that... forget about it.

Tell us... why do you specifically need Mojave...?
 
Bman70 said:
Oh right... it's a late (Nov?) 2019 6-core Intel Core i7. So not THAT new.. but still too new for Mojave from what I'm hearing. Apple customer service said MacBooks can never run anything older than what they shipped with.
Click to expand...
The 13" and 15" 2019 can be downgraded to Mojave as those models first shipped with 10.14.5. The 16" requires Catalina.
 
Bman70 said:
I just bought a new MacBook Pro, which I intended to downgrade to Mojave. However, clearly it can't since it shipped with Catalina. So, I thought of making a clone of my old MacBook Air hard drive which is Mojave, just to boot from when I need some older apps.

Is this as simple and straightforward as making a clone of the Air, then booting the MBP from it? While searching I've come across bits of gossip saying Catalina doesn't recognize Sandisk Extreme SSD as bootable, or has a different mode of creating volumes, etc., leading me to think there might be complications. Is SSD brand / type an issue, etc. So just thought I'd ask before starting such a project. Thanks for any pointers.
Click to expand...

No Macs can boot older than the OS that was shipped. So if it was shipped with Catalina, then you can only boot off Catalina. You can virtualize Mojave under Parallels off your old MB Air clone sparse bundle, but you just can't boot off it directly from the Macbook Pro. Also from the Bombich software site to address your gossip since you have a T2 Macbook Pro.

Don't install older versions of macOS than what your computer shipped with​

When you get a brand new Mac from Apple, it has a specific version of macOS installed on it, and further, a build that is specific to that exact model of Mac. If you install an older version or build of the OS, for example by cloning your older Mac to it, then it may behave unexpectedly, or it may not boot at all. If your new Mac is brand new, use Migration Assistant to migrate your data to your new Mac.

If your new Mac is just different, but not really hot off the production lines, then cloning another Mac to the new Mac may work fine. When cloning your source Mac to your new Mac, be sure that your source Mac has been updated to at least one later release than what came on the newer Mac. For example, if your newer Mac came with 10.12.4, update your source Mac to 10.12.5 before migrating. If such an update is not available, use the Migration Assistant(link is external) instead.

T2 and Apple Silicon Macs have "personalized" operating systems​

When macOS is installed onto a T2 or Apple Silicon Mac, the macOS Installer signs some of the startup resources with a code signature that is unique to your Mac. If you attempt to boot your Mac from the backup of some other Mac, your Mac will refuse to boot from that volume, claiming:

A software update is required to use this startup disk. You can update now or select another startup disk.
The "update" involves downloading system resources and then personalizing the backup volume's OS to the current Mac. This requires an Internet connection. Typically the application of that update works and the backup volume is then bootable, but various factors can cause that to fail. After confirming that the version of the operating system is compatible with the Mac you're trying to boot(link is external), there are two options to make this work:

T2 Mac​

Apple Silicon Mac​

Hold down the Power button on startup, select "Options", then press the Continue button. Then:

  • Choose "Startup Security Utility" from the Utilities menu, then change the Security Policy to Reduced Security, then proceed to attempt to boot from the backup volume or
  • Choose, "Share Disk..." from the Utilities menu, select a volume to share, then click the "Start Sharing" button. Attach the backup disk directly to another Mac, attach the Sharing Mac to the other Mac via USB or Thunderbolt, then restore the backup directly to the Sharing Mac's shared disk. CCC will ask macOS to personalize the destination Mac. This procedure requires macOS Catalina or later and an Internet connection.
 
Last edited:
iluvmacs99 said:
No Macs can boot older than the OS that was shipped. So if it was shipped with Catalina, then you can only boot off Catalina
Click to expand...
What you mean to say is that no Mac can boot an OS older than what first shipped on that particular model. An Intel Mac Mini bought today can still be downgraded to Mojave even if it ships with Big Sur on it.
 
iluvmacs99 said:
You can virtualize Mojave under Parallels off your old MB Air clone sparse bundle
Click to expand...

This sounds actually more appealing since no external drive is needed. I'll search for some tutorials, but if you know of any good ones that would be great. Is it a stable practical solution, or sort of a hack in the "just because you can doesn't mean you should" category? I'm doing this mostly to run some Adobe graphics programs I bought 5 years ago... still resisting the subscription model. But I might just go ahead and subscribe to Photoshop if the VM isn't worth the trouble. Thanks.
 
I run Mountain Lion and Sierra virtual machines on my 2018 Mini with Parallels. It works much better than I ever expected. I have thousands of dollars of old CAD, 3d and database software and they all run much faster in Parallels than they did on my old Macs. I also run Windows 10 in Parallels and have replaced three old computers with one Mini.

It isn't so obvious how to create Mac virtual machines in Parallels. Most of what I found on the web involved using the installers for the old versions, but you need to extract files from them, which I had problems with. But I found that it was very simple to create a VM from a bootable clone of my old Macs. Just attach the clone drive and choose it for a new VM. This is very quick, but it creates an empty VM which boots from the external clone (just like booting a real mac from a clone disk). So, after doing that, I just copied the system and everything I needed to the Parallels virtual disk using an old version of Carbon Copy.

I also have an old copy of Photoshop that works up through Sierra, but tends to crash often. So, I ended up just subscribing to the Adobe Photography plan, which is pretty reasonable. Same thing with my old version of MS Office, still worked but was slow and crash-prone, so I got Office 365. I don't like subscriptions either, but if the price is reasonable I just do it. However, that's a lot different from a $1500 CAD program that I only use occasionally but still need. The VM is a perfect solution for that. 🙂
 
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Bman70 said:
This sounds actually more appealing since no external drive is needed. I'll search for some tutorials, but if you know of any good ones that would be great. Is it a stable practical solution, or sort of a hack in the "just because you can doesn't mean you should" category? I'm doing this mostly to run some Adobe graphics programs I bought 5 years ago... still resisting the subscription model. But I might just go ahead and subscribe to Photoshop if the VM isn't worth the trouble. Thanks.
Click to expand...
It depends on which Adobe Photoshop version you own. If you currently have Photoshop CC 2015, then VM is worth it. It's not difficult to set it up either (look at Boyd01 description above) and you can install and try Parallels free for 14 days to see if it works with all your older software. If you're looking mainly to run much older Photoshop software like CS2 and CS5 however, it's better to stick with an older Mac, connect it to a network and use screen share. Besides CS2 and CS5 don't work with Mojave as they crash often or don't run at all even under VM, which is why I still have older Macs. I can't justify paying the subscription model since I had retired from the graphics industry a few years ago, but I still need to use my older Photoshop software to do my hobby stuff. If you're still on a paying gig, then you may be able to justify subscribing to it. So for me, I use a combination of VM and old Intel/PPC Macs to run many of my older 32bit software and even a handful of paid PowerPC applications. VM is great because you can run many concurrent OS simultaneously and exchange files seamlessly.
 
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iluvmacs99 said:
It depends on which Adobe Photoshop version you own. If you currently have Photoshop CC 2015, then VM is worth it. It's not difficult to set it up either (look at Boyd01 description above) and you can install and try Parallels free for 14 days to see if it works with all your older software. If you're looking mainly to run much older Photoshop software like CS2 and CS5 however, it's better to stick with an older Mac, connect it to a network and use screen share. Besides CS2 and CS5 don't work with Mojave as they crash often or don't run at all even under VM, which is why I still have older Macs. I can't justify paying the subscription model since I had retired from the graphics industry a few years ago, but I still need to use my older Photoshop software to do my hobby stuff. If you're still on a paying gig, then you may be able to justify subscribing to it. So for me, I use a combination of VM and old Intel/PPC Macs to run many of my older 32bit software and even a handful of paid PowerPC applications. VM is great because you can run many concurrent OS simultaneously and exchange files seamlessly.
Click to expand...

It's the one you didn't mention – CS6! The suite has Illustrator, Photoshop and InDesign, all of which I use on occasion. They all seem to run great on my Air running Mojave. (You just have to put them in the "let these apps run your computer" section in Settings. And of course install the older Java.) As Boyd01 mentioned, the photography plan isn't a bad price, and includes Lightroom, so I might do that. But if Parallels is as effective as it sounds, I think I'll attempt a Mojave or HS VM on the Catalina MBP. The network screen share would be a close second though.
 
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Boyd01 said:
I run Mountain Lion and Sierra virtual machines on my 2018 Mini with Parallels. It works much better than I ever expected. I have thousands of dollars of old CAD, 3d and database software and they all run much faster in Parallels than they did on my old Macs. I also run Windows 10 in Parallels and have replaced three old computers with one Mini.

It isn't so obvious how to create Mac virtual machines in Parallels. Most of what I found on the web involved using the installers for the old versions, but you need to extract files from them, which I had problems with. But I found that it was very simple to create a VM from a bootable clone of my old Macs. Just attach the clone drive and choose it for a new VM. This is very quick, but it creates an empty VM which boots from the external clone (just like booting a real mac from a clone disk). So, after doing that, I just copied the system and everything I needed to the Parallels virtual disk using an old version of Carbon Copy.

I also have an old copy of Photoshop that works up through Sierra, but tends to crash often. So, I ended up just subscribing to the Adobe Photography plan, which is pretty reasonable. Same thing with my old version of MS Office, still worked but was slow and crash-prone, so I got Office 365. I don't like subscriptions either, but if the price is reasonable I just do it. However, that's a lot different from a $1500 CAD program that I only use occasionally but still need. The VM is a perfect solution for that. 🙂
Click to expand...

This sounds like a great option. So you just install Parallels, then when it asks to create the VM you pick your bootable clone? That does sound quicker than the other tutorials I've been reading. You no longer need the clone drive once you've copied the system to the Parallels "disk" correct? I agree the Photography plan is reasonable, if I didn't use Illustrator I'd go for it. I still probably will just for Lightroom.
 
Bman70 said:
It's the one you didn't mention – CS6! The suite has Illustrator, Photoshop and InDesign, all of which I use on occasion. They all seem to run great on my Air running Mojave. (You just have to put them in the "let these apps run your computer" section in Settings. And of course install the older Java.) As Boyd01 mentioned, the photography plan isn't a bad price, and includes Lightroom, so I might do that. But if Parallels is as effective as it sounds, I think I'll attempt a Mojave or HS VM on the Catalina MBP. The network screen share would be a close second though.
Click to expand...
Oh right, I forgot about that! You can probably tell just by how long I'm out of the upgrade game. 🙂 Try Parallels and see how you like it and the cost of trial isn't high either. 🙂
 
Bman70 said:
So you just install Parallels, then when it asks to create the VM you pick your bootable clone? That does sound quicker than the other tutorials I've been reading. You no longer need the clone drive once you've copied the system to the Parallels "disk" correct?
Click to expand...
Correct. When you create a new virtual machine I chose the option to use a disk image (IIRC) , it found the clone and offered to create a VM. That only took a few seconds, which surprised me. Took awhile to figure out that it had created a VM with an empty disk and was booting directly fron the clone.

However, you may not be too keen on creating a 256gb (or whatever) virtual disk just to run a few old programs - I wasn't. So you can use Carbon Copy to only clone the folders you want to the virtual disk. Alternately, you could prune down the clone to a reasonable size before creating the VM.
 
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