Are multiple OS's possible?

[shep666]

I have recently acquired a new iMac with El Capitan already installed. I would like the option of also starting up with Yosemite or Snow Leopard. Is this possible? So far, it seems that El Capitan has resisted the installation of an "older system."

Thanks for any suggestions.

 

[Cory Cooper]

Hello and welcome.

You can run multiple versions of OS X, just not on the same hard drive partition. You would need to either partition your internal hard drive to allow multiple version installs, or simply use an external hard drive (multiple partitions for multiple OS versions) for the the other OS versions.

C

 

[shep666]

On my old iMac running ) OS X 10.5 I have 3 external hard drives. I wanted to install snow leopard on one of them (NOT my internal start-up drive) but when I clicked on the Install Mac OS X button, I got this message: You can’t use this version of the application “Install Mac OS X” with this version of OS X. So my question is how do I install snow leopard on an external hard drive?

 

[Cory Cooper]

Ah...OK.

You would need to make a bootable installer disk first then. There are many ways to do this using either a USB flash drive or an external hard drive as the installer. The easiest is DiskMaker X.

C

 

[shep666]

I've tried carbon copy cloner and diskMaker. The resulting thumb drive has not been bootable. When I hold down Option at start-up, the usb drive shows up as an option, but in fact the iMac will not start if it is selected. It does not show up at all if I look at start-up in systems preferences.

Then I came across this from Apple:

Use the version of OS X that came with your Mac, or a compatible newer version
Your Mac is designed to work with compatible versions and builds of OS X. If you try
to use a version or build of OS X that's not compatible with your Mac, your computer
might behave unexpectedly.
Avoid using versions of OS X that are older than what came with your Mac. If you copy older system files
from another computer to your Mac, or try to use startup disks designed for older computers, you might
see one or more of the following:
Your Mac doesn't start up, or you see a prohibitory symbol at startup . . .


So . . . does this put the kibosh on my attempts to install an older system alongside El Cap?

 

[Cory Cooper]

If you are trying to install an older OS X version on an iMac that came with El Capitan, yes, you are out of luck. Newer hardware will only run versions of OS X that are equal to or newer than what they shipped with.

If you are trying to install Snow Leopard on and external drive on the older iMac, if you successfully make a bootable USB installed, you should boot from it, then attempt the install on one of the externals.

Am I understanding you correctly?

C

 

[shep666]

If you are trying to install an older OS X version on an iMac that came with El Capitan, yes, you are out of luck. Newer hardware will only run versions of OS X that are equal to or newer than what they shipped with.

If you are trying to install Snow Leopard on and external drive on the older iMac, if you successfully make a bootable USB installed, you should boot from it, then attempt the install on one of the externals.

Am I understanding you correctly?

C

Alas! I fear you understand correctly. I have been trying to install Snow Leopard on a new iMac that came with El Cap pre-installed. Looks like I can't do that. Is there no work-around?

 

[Cory Cooper]

At least we are on the same page. Unfortunately, there is no work-around, due to the older OS versions not supporting the newer hardware.

C