Virtualizing my Sierra OS onto Big Sur with VirtualBox

Discussions related to using VirtualBox on Mac OS X hosts.

Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby MacJunk » 3. May 2021, 15:27

No matter what I try I cannot get my virtualized .dmg from my tangible MacOS Sierra machine to run on VirtualBox 6.1.22 on Big Sur. Based on research I've disabled the I/O Cache on the virtual optical drive, moved the virtual optical drive to its own IDE controller, and even tried my other Mac machine images that are known working and starting up.

Any other things to try? Thank you!
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby MacJunk » 8. May 2021, 00:07

I tried a detailed uninstall/install from this forum and here is a log file if anyone can help. Thank you!
Attachments
log.zip
VBox Install Log Mac OS X Big Sur
(3.38 KiB) Downloaded 4 times
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby mpack » 8. May 2021, 10:33

Please provide a VM log file. Make sure the VM is fully shut down, then right click it in the manager UI. Select "Show Log" and save "VBox.log" (no other file) to a zip file. Attach the zip here.
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby MacJunk » 8. May 2021, 14:19

Here you are. Thank you so much!
Attachments
vbox.zip
Vbox.log File
(25.04 KiB) Downloaded 4 times
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby mpack » 8. May 2021, 17:00

I'm seeing an error in the log, VERR_NOT_SUPPORTED, when it tries to boot from the dmg. This implies that it isn't a bootable optical disk image.

Programs shipped on optical disks don't install themselves by magic. To be installed on a blank PC the CD/DVD image itself has to be bootable (i.e. have a valid boot sector), and after booting into a mini OS it runs an installer executable that needs to exist on the CD/DVD as well.

I don't know what you have there, but it isn't a bootable DVD having the features I mention.

If you wanted to image a hard drive, rather than install MacOS from fresh, then you need to create a recognizable hard disk image, i.e. VMDK, VDI, etc.
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby MacJunk » 9. May 2021, 04:47

I may have figured this out. I was creating a VDI file instead of a VHD for the hard disk. Moving forward with a Mojave install right now. Thank you!
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby mpack » 9. May 2021, 09:47

?? Your original post only mentions dmg, not VDI or VHD.

AFAIK, VirtualBox treats dmg the same way as ISO, i.e. it's a removable media for optical drives only.

VDI/VMDK/VHD are for images of hard disks, and they would be mounted differently in the VM - i.e. mounted directly instead of creating a drive and then assigning removable media to it.

VHD is a really poor format. I left it out of the discussion because I wouldn't recommend it to anyone, particularly not someone on a MacOS host (*). But using it would not cause this error.

VDI is the native format in VirtualBox, and was the correct choice for a hard disk image, provided you found a disk imaging tool that creates it.

(*) VHD has some utility on Windows hosts since other Windows tools may be designed to work with it, which for some users may outweigh the design risks (i.e. the tendency to be easily corrupted). However even on Windows, Microsoft deprecated the format some time ago and now recommend VHDX instead. FYI despite the name similarity, VHDX is a completely different format. VHD has no utility on MacOS hosts that I'm aware of.
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby mpack » 9. May 2021, 10:01

A thought occurs - so just to be clear: you should be creating a recognizable hard disk image directly from the original full drive, not by converting the DMG, which is probably already ruined - but I can estimate the chances of that better if you tell me how the DMG was created.
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby MacJunk » 9. May 2021, 13:59

When I first created a virtual machine, I was originally choosing VDI as the blank "hard drive" in which to install the OS from the DMG installer created from an install disk (my "optical drive"). I forever had the FATAL: no bootable medium found.

When I switched to VHD as the format for the blank hard drive things worked (I don't know why). If it's a sub-par format for performance I can definitely see it, even on an SSD with 12GB (of my 16GB) of RAM in the VM.

Now that I have a bootable drive, however, what are the chances of me making a superior VDI, starting up, then cloning the OS to that? Would it provide superior performance?

Thank you for your thorough advice!
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Re: Virtualizing my Sierra OS onto Big Sur with VirtualBox

Postby mpack » 9. May 2021, 14:24

Sorry, there is simply no sense to the comment that choosing VDI had any detrimental effect on anything. You get "no bootable medium" when the medium is not bootable, not because of the container format used. Hence there's no way to speculate on why something nonsensical could make sense. The only explanation I can think of is treating correlation as causation.

If things happened after the switch to VHD then it's because something else changed as well. For example, MacOS expects an EFI BIOS, so giving it a VDI imaged from a working disk and not enabling EFI will give you "no bootable medium". If you tried VHD and also turned on EFI then the latter is what made the difference.


I'm also getting concerned that you keep contradicting information you already gave. For example you originally referred to your DMG as "my virtualized .dmg from my tangible MacOS Sierra machine", which I took to mean: "an DMG image of a physical hard disk" (but created how?). However in your latest post you say that your dmg contains an installer: if it was imaged from a working drive then it does NOT contain an installer, it's an image of an already installed system (and p.s. can't be used sensibly as an optical disk boot image). And it still doesn't make clear how a hard disk image was turned into an optical disk image (DMG).

Note: I'm not a Mac user, but I vaguely recall that DMG is not limited to optical disk images. However VirtualBox's use of DMG AFAIK is limited to optical disk images, where it is treated the same as ISO. VirtualBox will therefore expect the DMG to contain an ISO-9660 (or successor) filesystem. In order to be bootable it will also have to contain a boot sector, and in order to be useful for installing an OS, you will have to have created an installer script and put an installer executable in the root folder of the ISO. Please state clearly if you did any of these things.
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