bought a 27" 2020 iMac, i7 w/ Ventura

[uptimework]

On ebay, I just bought a 27" 2020 iMac, i7-10700K 3.80GHz, 64GB, 1TB SSD, 5K, Radeon Pro 5700 XT 16GB with Ventura installed. It came with no installer. I wanted to install another instance of the os on a separate partition. I used to do this kind of thing all the time but it has not been seamless. I created an APFS volume in Disk utility > Partition. I first tried Catalina via Time Machine and it rebooted to the crossed out circle. Now I am giving up on that dont want to get into OpenCore stuff so I now just want to install Ventura (unless there is a better recent one).

So in terms of installing Ventura is there an easy way to install / copy Ventura onto the other partition? How about without using Apple update? Where can I get the installer without using Apple update?

 

[uptimework]

note i tried downloading ventura in apple software update and it fails. i have a bad connection and dont want to use apple update anyway

 

[uptimework]

also note in terminal

softwareupdate —list-full-installers

does not list anything!

 

[uptimework]

did time machine backup of current (brand new fresh) install of ventura > tried to install to partition = you can not install from time machine...must install venturea then use migration assistant???? this is ay too hard

 

[Bigwaff]

Hope this helps -

Use more than one version of macOS on Mac - Apple Support

If you install a compatible macOS on an additional internal or external storage volume, your Mac can start up from either volume.

support.apple.com

 

[uptimework]

Ok issues was (unlike previous) must first install os then use migration assistant. Which also means forcing me to download os instead of using time machine. Not as good !

 

[davidlv]

Ok issues was (unlike previous) must first install os then use migration assistant. Which also means forcing me to download os instead of using time machine. Not as good !

A lot of the older common knowledge concerning Mac OS has changed over the years. Your understanding needs a little updating. First Ventura is the latest version of macOS, that is why you didn't see anything new using the softwareupdate command.
See: https://www.macworld.com/article/673697/what-version-of-macos-can-my-mac-run.html
Since the release of Ventura at least, maybe prior to that, having two instances of the latest system installed can mess up one or the other, or even both.
You can read up on that, and the reasons that a bootable backup is no longer the best backup option, on the Carbon Copy Cloner blog. <https://bombich.com/> CCC by the way is a very good backup application, and IMO well worth the reasonable price.
I have found that it is possible to install Monterey on an external USB 3.0 disk, and it will stay stable and usable, while having a second bootable Ventura install, either on the internal SSD or even on an external disk presents issues.
Your experience may be different, but based on my experience, the conclusion is as shown below:
Install Big sur or Monterey on an external SSD and set it up so you can boot to it and do your work if the Ventura install gets borked.
BTW, OCLP is a good way to use an old non-compatible computer with Big Sur, Monterey, or Ventura. Your new 2020 iMac will be able to run Sonoma when it is released later this year.
The OCLP developers are now hard at work trying to get Sonoma, the next macOS, now in Beta, viable on older hardware, but it is a work in progress.
You can find Apple system installers at several sites, but the easiest is:

macOS 12 Monterey Full Installer Database. Download Directly from Apple!

Download macOS Monterey full installer with one click straight from Apple! Every version of Monterey Beta & Final available all in one place!!

mrmacintosh.com

 

[uptimework]

Yes I am outdated I have kept the same macs for years / as long as possibe. Last time I did disk management I did all partitioning which I guess is not how it is done now. https://support.apple.com/en-us/HT208891

But as I understand you are saying do not install any version on any container or partiton (or even internal drive)...but instead do it on an external....and it should not be another Ventura but Montery or Big Sur.

I do have ccc I would have to update it are you saing that is better than : install os then use migration assistant? (as advised by apple support)

 

[davidlv]

Yes I am outdated I have kept the same macs for years / as long as possibe. Last time I did disk management I did all partitioning which I guess is not how it is done now. https://support.apple.com/en-us/HT208891

But as I understand you are saying do not install any version on any container or partiton (or even internal drive)...but instead do it on an external....and it should not be another Ventura but Montery or Big Sur.

I do have ccc I would have to update it are you saying that is better than : install os then use migration assistant? (as advised by apple support)

Now, with the advent of APFS, using "volumes" is more convenient than partitions. They share the same disk space, in a dynamic manner, and you can delete and create them at will.
If you are installing a new system on a disk with no prior system installed, yes, installing the OS (from a USB installer disk) and then using migration assistant is the best way to get a stable system up and running quickly. That is why having a CCC backup is great, you just use the migration assistant to use that CCC backup for the migration.
When you have a good system already installed, the new common knowledge is don't install another "instance of the same system" on a new volume on the same disk. I have had bad experiences with that configuration (2 Ventura installs), where one system got completely messed up and the other was a little off, finally had to wipe that system too and reinstall.
With a modern Ventura install, there is no need for another system anyway, but if you want to have one, I suggest doing it on an external SSD, using Monterey, which will get security updates until the end of 2024.

 

[uptimework]

That is why having a CCC backup is great, you just use the migration assistant to use that CCC backup for the migration.
.....
With a modern Ventura install, there is no need for another system anyway

Why CCC instead of time machine?

Also, pertaining to CCC and/or time machine. The old way of "all in one" gave me assurance that exactly what is on source would go to destination. I dont know how migration assistant works but I dont see how it could know to migrate certain apps along with all their dependancies e.g. Logic > Waves plug-ins > Waves presets + Waves Sample files or Toontrack EZ Drummer > EZ Drummer samples folder or photoshop > photoshop actions + photoshop plugins + ps plug-in presets.

Yes well macs still seem to have more longevity than windows without getting somehow corrupted. But I dont get how Ventura would be different than earlier mac versions in the sense of needing or not needing a second "just in case" install.

In my case I am also doing different stuff like pro audio on one and ai stuff on another so out of an abundance of caution I would like to try and have clean os's for each. In any case, I will take the advice of not installing in internal...good to know.

 

[davidlv]

Why CCC instead of time machine?

Also, pertaining to CCC and/or time machine. The old way of "all in one" gave me assurance that exactly what is on source would go to destination. I don't know how migration assistant works but I don't see how it could know to migrate certain apps along with all their dependancies e.g. Logic > Waves plug-ins > Waves presets + Waves Sample files or Toontrack EZ Drummer > EZ Drummer samples folder or photoshop > photoshop actions + photoshop plugins + ps plug-in presets.

Yes well macs still seem to have more longevity than windows without getting somehow corrupted. But I dont get how Ventura would be different than earlier mac versions in the sense of needing or not needing a second "just in case" install.

In my case I am also doing different stuff like pro audio on one and ai stuff on another so out of an abundance of caution I would like to try and have clean os's for each. In any case, I will take the advice of not installing in internal...good to know.

Your question about CCC (or SuperDuper) versus Time Machine is actual a common one, and various people have various opinions. Some use both. I have had excellent results with CCC, so it gets my vote. If You have a separat external disk you can use for Time Machine, try it.
As for copying file, apps and their dependancies, Migration Assistant replaces everything that is on the specified backup disk, and by default, CCC copies everything so you are covered there. I have no certain knowledge if that is the same with Time Machine (but I assume so).
What is the internal storage on your 2020 iMac? 1 SSD alone? or a Fusion drive?

 

[uptimework]

Interesting you asked that I was just looking at if i should change my setup based on this conversation. It has a 1 TB SSD. After what you guys said i will opt to get an external for a second OS as needed. The way i currently have the allocations was based on what i was going to do based on my previous legacy approach. For example, right now I have it partitioned and labeled one bootcamp and one Macintosh HD2...both are still blank. Only thing in use is Macintosh HD and Files has some installers on it. And with the difference between APFS and Partitioning I am still somewhat confused as to what i should do now...just delete all except Macintosh HD and then add whatever I want inside the container of Macintosh HD? note: bootcamp is again what i considered doing (not a must) but i was just going to benchmark some Stable Diffusion stuff against a PC I just got. Is bootcamp also an issue now?

 

[mitico7327]

Hope this helps -

Use more than one version of macOS on Mac - Apple Support

If you install a compatible macOS on an additional internal or external storage volume, your Mac can start up from either volume.

support.apple.com

how do you do the opposite? I am on Sonoma and want to install Ventura (older) on a separate partition? Sonoma won't let me.

 

[Bigwaff]

how do you do the opposite? I am on Sonoma and want to install Ventura (older) on a separate partition? Sonoma won't let me.

What is your Mac model and year?