Creating a 10.10 partition while running 10.11

[YassRebel]

Hello everyone, while I have seen similar posts in regards to installing a different Mac OS on an external hard drive, I haven't seen anywhere the specifics to what I'm trying to do and hopefully I can get the help in this forum.

I am currently running El Capitan (10.11.6) OS in my Macbook Pro mid 2015. I just got an external SSD which I partitioned because I want to install and run Yosemite (10.10) OS on it because of some software compatibility issues I have which I need to run on Yosemite.

Obviously, if I try to open the Yosemite installer I get the This copy of the “Install OS X” application is too old to be opened on this version of OS X message. As an alternative, I tried creating a bootable USB drive installer of the Yosemite OS, which can be seen from the System Preferences > Startup Disk menu as well as when I restart the Macbook holding Option (Alt). The issue I am having is, when I select the installer USB drive from this screen, I get a black screen with the NO ENTRY sign.

After searching all over the internet (youtube, google, tutorials, forums, etc), I haven't been able to find a way to do what I'm trying to do.

So, do any of you have any idea how to achieve this?

Thank you in advance for any help or pointing me in the right direction.

 

[jbarley]

Do a Google search for "how to bless a boot volume", seems I've read about this problem before.

 

[DeltaMac]

Or, you can use one of the installer disk-making apps, such as DiskMakerX, or Install Disk Creator.

If your Yosemite installer app is for OS X 10.10 - then that won't work on your mid-2015 MacBook Pro. You need at least 10.10.4 to get an installer that will boot your MBPro. Yes, it shipped with 10.10.3, but you would need the build that actually shipped with your MBPro. Most up-to-date installer app would be 10.10.5 - which should work fine on your 2015.

 

[YassRebel]

Or, you can use one of the installer disk-making apps, such as DiskMakerX, or Install Disk Creator.

If your Yosemite installer app is for OS X 10.10 - then that won't work on your mid-2015 MacBook Pro. You need at least 10.10.4 to get an installer that will boot your MBPro. Yes, it shipped with 10.10.3, but you would need the build that actually shipped with your MBPro. Most up-to-date installer app would be 10.10.5 - which should work find on your 2015.

As of right now I can't really say which version I have since I can't open the installer. I downloaded it a while back when I upgrades my Macbook Pro. I'm going to try to find a newer version of Yosemite just in case.

 

[DeltaMac]

You don't have to open the installer to view the version. If you have the flash drive (even if it doesn't actually boot your MBPro), plug it in to your MBPro, then open System Preferences/Startup Disk pane. Bootable disks will appear there, and will show the OS X version that installer will boot from - which is the same version that will install.

 

[YassRebel]

@DeltaMac Yeah, I'm screwed. It is the 10.10.2 version.

 

[DeltaMac]

Well, that explains THAT issue
All you need is the more current version. Not so easy if you have never purchased Yosemite (and it would be in the Purchased tab in your App Store)
Maybe someone else will chime in with a good link for Yosemite. And, shouldn't be too hard to get in a torrent, I suppose. Some will say that's a not-quite-safe way to get it, but sometimes that's the chance that you may take, as long as you can be assured that you get the version that you want.

Sometimes you can ask at an Apple store, or an AASP, and you can get a copy of the Yosemite installer, depends on where you are, and who you talk to.
Or, maybe you know an experienced Mac-er, who would help you out.

 

[YassRebel]

Well, that explains THAT issue
All you need is the more current version. Not so easy if you have never purchased Yosemite (and it would be in the Purchased tab in your App Store)
Maybe someone else will chime in with a good link for Yosemite. And, shouldn't be too hard to get in a torrent, I suppose. Some will say that's a not-quite-safe way to get it, but sometimes that's the chance that you may take, as long as you can be assured that you get the version that you want.

Sometimes you can ask at an Apple store, or an AASP, and you can get a copy of the Yosemite installer, depends on where you are, and who you talk to.
Or, maybe you know an experienced Mac-er, who would help you out.

You were absolutely right. The OS version was the issue. Since it was in my purchased history I was able to download a copy and make a working bootable USB drive. Thank you for all the info!!