running Catalina and High Sierra on same Mac

[odamizu]

Success! I now have a bootable SSD running macOS!

Originally Posted by pwalker8

When I boot off the external drive, I can't even see the internal drive. I'm sure I can use disk utility to make it accessible, but by default it's not visible ...

When I boot off the external drive, after I log in and the desktop appears, a dialog box pops up offering to show me the internal drive in return for a password. If I decline, I can use disk utility to mount it.

What's interesting is that I have 2 user accounts on my Mac, an admin account (the first account created) and a standard account, and entering the password for either account will open up the entire internal drive and allow me (or anyone!) to view everything in the Home folder of the admin account. But permission is denied to view the Home folder of the standard account. Even when I enter the password for the standard account, the admin account is wide open and the standard account is locked down. Anyone have any ideas why this is?

Originally Posted by kyteflyer

I didnt think I needed a clone either: I was making one (it was set to auto update weekly) but didn't realise I needed it until the internal drive in my iMac died, and the clone simply took over. I had neither the time, money, nor the energy to cart the iMac in to the shop to have the drive replaced until a month later. It was good to have had that clone working.

So, what clone software do you prefer?

[pwalker8]

Glad you have it working.

[asleyam]

I think an administrator account is restricted from accessing another user’s account, which makes sense otherwise the admin could access that user’s private files.

I only have one account so never have permissions issues accessing my account from external drives running another Mac install.

[pwalker8]

Originally Posted by asleyam

I think an administrator account is restricted from accessing another user’s account, which makes sense otherwise the admin could access that user’s private files.

I only have one account so never have permissions issues accessing my account from external drives running another Mac install.

That's pretty much how I have my mac set up, one account. In unix land, it's traditional to have a root and then individual accounts, but while the mac may be unix underneath, it's not just linux with a better UI bolted on it.

[odamizu]

Originally Posted by asleyam

I think an administrator account is restricted from accessing another user’s account, which makes sense otherwise the admin could access that user’s private files ...

Yes, that makes sense. But what I've found is that if you have multiple accounts, regardless of whether they are admin or standard, the first/original/root account is accessible to all users if the Mac is booted from an external drive.

ETA: https://www.macobserver.com/tips/qui...evault-access/

[helpplease]

Hi,
@odamizu
I tried to boot off my old SDD harddrive in an external caddie (running high Sierra 10.13.6) from new MacBook Air (shipped with Catalina), and it refused to allow it. Refused even after removing secure security boot feature of Catalina (eg recovery mode, utilities/security settings and change allow boot external, and change no security).

On boot up, startup disk set to my old harddrive running high Sierra, gave me white circle with line thru it. Googled that "white circle with line thru it" and said it's forbidden to downgrade from shipped version.

I'm thinking, really? This must be possible some how. I have a full working external harddrive (SSD) just my MacBook Pro motherboard died, so I have a new MacBook Air. I don't want Catalina as presents all sorts of unplanned problems with applications and ebooks.

Any ideas?

I am up to trying what this thread is suggesting dual boot. But if dual boot works, then it should work from an external. Or maybe dual boot only works from older MacBooks (pre Catalina ) where the dual boot includes high Sierra. So you can dual boot for OS X shipped with and later, but not earlier. I don't know.

I hope it makes some sense.

[pwalker8]

Originally Posted by helpplease

Hi,
@odamizu
I tried to boot off my old SDD harddrive in an external caddie (running high Sierra 10.13.6) from new MacBook Air (shipped with Catalina), and it refused to allow it. Refused even after removing secure security boot feature of Catalina (eg recovery mode, utilities/security settings and change allow boot external, and change no security).

On boot up, startup disk set to my old harddrive running high Sierra, gave me white circle with line thru it. Googled that "white circle with line thru it" and said it's forbidden to downgrade from shipped version.

I'm thinking, really? This must be possible some how. I have a full working external harddrive (SSD) just my MacBook Pro motherboard died, so I have a new MacBook Air. I don't want Catalina as presents all sorts of unplanned problems with applications and ebooks.

Any ideas?

I am up to trying what this thread is suggesting dual boot. But if dual boot works, then it should work from an external. Or maybe dual boot only works from older MacBooks (pre Catalina ) where the dual boot includes high Sierra. So you can dual boot for OS X shipped with and later, but not earlier. I don't know.

I hope it makes some sense.

As a rule of thumb you can't run a machine on a IOS version prior to when the first model of that machine was shipped. Mostly, it's a situation when the older IOS version doesn't have the device drivers needed for the newer hardware. Thus I can boot my old mac mini and iMac on an external drive with Sierra on it, but not my 2018 macbook pro. I tried the same thing that you did (but with Sierra) and got the same error.

I understand there are hacks you can do to force it to try, but I suspect you may run into so odd issues. For me, it wasn't worth the effort. I can book my iMac on an external drive with Sierra, which suits my needs. If you really need to run High Sierra, then you might consider getting an older machine. I'm not sure what incompatibilities you are running into.

[odamizu]

Originally Posted by helpplease

Hi,
@odamizu
I tried to boot off my old SDD harddrive in an external caddie (running high Sierra 10.13.6) from new MacBook Air (shipped with Catalina), and it refused to allow it ...

Originally Posted by pwalker8

As a rule of thumb you can't run a machine on a IOS version prior to when the first model of that machine was shipped. Mostly, it's a situation when the older IOS version doesn't have the device drivers needed for the newer hardware. Thus I can boot my old mac mini and iMac on an external drive with Sierra on it, but not my 2018 macbook pro. I tried the same thing that you did (but with Sierra) and got the same error.

I understand there are hacks you can do to force it to try, but I suspect you may run into so odd issues. For me, it wasn't worth the effort. I can book my iMac on an external drive with Sierra, which suits my needs. If you really need to run High Sierra, then you might consider getting an older machine. I'm not sure what incompatibilities you are running into.

I think pwalker8 is correct.

I was taking a Mac that shipped with High Sierra and used an external SSD to boot it with Catalina. I've not tried the reverse.

Also, from Apple: "The version of macOS that came with your Mac is the earliest version compatible with that Mac."

Have you considered a VM? That is supposed to work.

[helpplease]

Thankyou @pwalker8 and @odamizu.

That is a learning for me! I had no idea firmware was so impactful in OS X world, or maybe computer world. I realise now I should of purchased an old MacBook and waited until all the apps are mature in 64 bit, rather than this new MacBook Air. Geez...

I will try VM solution (With how-to using the free Parallels lite by imore)

Thankyou for both of your help. Greatly appreciated.

[helpplease]

VM Solution using Parallel was a breeze. Have old harddrive migrated to macOS VM host. All apps working. Ebook world back.
Followed imore instructions.
Thankyou for VM tip @odamizu

Then I discovered someone done the VM macOS host on their iPad Pro. Amazing in my view.
https://www.imore.com/ipad-pro-so-gr...-hate-yourself

[pwalker8]

Originally Posted by helpplease

VM Solution using Parallel was a breeze. Have old harddrive migrated to macOS VM host. All apps working. Ebook world back.
Followed imore instructions.
Thankyou for VM tip @odamizu

Then I discovered someone done the VM macOS host on their iPad Pro. Amazing in my view.
https://www.imore.com/ipad-pro-so-gr...-hate-yourself

I'm glad it worked for you.

Yea, I have one software package that requires Sierra. It's a software package that I use perhaps once a month, but it's something that I really need, so I keep an old mac mini around to run Sierra. I have the external hard drive so if the mac mini kicks the bucket, I have a fall back.

[odamizu]

Originally Posted by helpplease

VM Solution using Parallel was a breeze. ...
Thankyou for VM tip @odamizu