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Unable to install OS X El Capitan on new hard drive (Early 2008 Mac Pro)

I have an early 2008 Mac Pro with the original 320MB hard drive. It is currently running OS X 10.11.6. I would like to install the same OS onto a ;eager (1TB) hard drive and then I pan to sell the machine. I downloaded the El Capitan installer but for some reason the OS X installer does not allow me to select the new hard drive as the destination. The new disk is grayed out and there is a yellow warning triangle with an exclamation point inside of it. The warning message reads: "OS X can't be installed on this disk. OS X isn't installed" (see attached screenshot). This makes it sound like the installer needs to see the previous version on the disk before it will install it. Does anyone have any suggestions? Thanks!



Mac Pro, OS X 10.11

Posted on May 22, 2020 6:49 PM

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Posted on May 22, 2020 7:43 PM

At this point you are not installing El Capitan, what is happening is the InstallMacOSX.pkg is creating the Install OS X El Capitan.app which will appear in your Applications folder, it is this you use to install El Capitan.

So at this point select your Apollo disk.

8 replies

May 22, 2020 7:05 PM in response to jhorner

Did you download the El Capitan installer from here?

http://updates-http.cdn-apple.com/2019/cert/061-41424-20191024-218af9ec-cf50-4516-9011-228c78eda3d2/InstallMacOSX.dmg


Use these instructions to install the installer and to run the installer:

https://support.apple.com/kb/HT206886


You can also create a bootable macOS USB installer using these instructions:

https://support.apple.com/en-us/HT201372


Make sure the drive is properly erased. Within Disk Utility make sure to select the physical drive and not the "Untitled" volume. Erase the physical drive as GUID partition and MacOS Extended (Journaled). Now try installing macOS to the external drive.

May 25, 2020 9:25 AM in response to Eau Rouge

thank you... this process is unnecessarily complicated mostly due to the fact that the documentation is not clear at all about this. for one, you are not downloading the El Capitan installer from the El Capitan installer link. you are downloading the installer for the el capital installer. thank you for providing that insight or I would have been stuck for a while!


it is also not documented anywhere that I saw, that the installer for the El Capitan installer could not be installed on the target drive for whatever reason, but had to be installed on my active startup drive. this is a little counterintuitive since I was trying to install El Capitan on a different drive. so naturally one would assume they could install something called the El Capitan installer on that target drive.


I love yo apple but it would be nice if you could provide better (clearer) step by step instructions about this!

May 25, 2020 9:36 AM in response to HWTech

thank you for your response!! those are the links from which I had downloaded the installer. I was also following the instructions found at the second link. the problem is, even in the instructions, the title of step 4 is "Download OS X El Capitan" when you are actually downloading something 2 degrees of separation from OS X El Capitan, namely, the installer that installs the installer for OS X El Capitan. similarly, step 5 is titled "Install the Mac OS Installer" when you are actually installing the installer that then installs the Mac OS X installer. So again the instructions are VERY misleading. So naturally, when I wanted to install it on a spare drive, I attempted to install it there but it appears that the installer installer cannot be deployed that way, hence the grayed out drive when trying to specify where to install the software. Even the dialog window when I tried to install the downloaded installer said, "Select the disk where you want to install the OS X software." The disk I wanted to install it on was the "Untitled" disk, but the dialog should have said "Select the disk where you would like to launch the installer software that will in turn install the OS X software (Note: the location to install the installer software that will install OS X cannot be on the target disk for the OS X software itself)". Very strange Apple!!


but thank you HWTech for the speedy reply and the helpful links ;-)

May 25, 2020 9:55 AM in response to jhorner

Well Sections 4 to 6 in the How To Upgrade To El Capitan explain the procedure.

Another clue in the first installer window is that it says that this will take 7MBs of hard drive space,

no OS take up that little amount of space, El Capitan once installed takes up between 20- 30GBs.

Apple hasn't taken into account that users may be installing the OS to another external disk.


Apple is not here just users like yourself.

May 25, 2020 10:56 AM in response to Eau Rouge

thanks eau rouge,


i think i was already a little annoyed with the process because i had a previous version of the "Install OS X El Capitan.app" on my startup drive (probably from when the computer itself was originally upgraded to El Capitan) that i was attempting to use but after going through the install process several times, each one of which took about 30 minutes, before getting an error message that the software could not be installed (i forget the exact error message itself... something to the effect of no valid packages found or something?). So i think that must have just been a corrupted version of the installer? I downloaded a fresh copy of the installer for the install app and that is when i arrived at the point that lead to my original post here. Thanks to your reply and that of HWTech I realized that it was not asking me where i wanted to install OS X but only where i wanted to install the installer... after that realization it was easy and the newly installed installer app worked fine.


Simply following the Apple instructions would work fine if you were upgrading the startup drive, but there should be some sort of note at the beginning for the option you want to install on another drive... that doesn't seem like such a remote possibility.


on a different note, i participate on other user forums (for filemaker pro, or adobe photoshop, for example) and on occasion a tech or support person from one of those companies will post a reply. Does that not ever happen on this forum?


thanks again for your help! :-)

May 26, 2020 12:34 AM in response to jhorner

No this is a user to user forum, occasionally you will get somebody called a community specialist.


Apples instructions can be quite vague at times.


In October 2019 the certificates for many of Apples legacy OS's expired, your original El Capitan installer

which was giving the error message was probably downloaded prior to October 2019. If you had changed the date and time on your mac to a date prior to October 2019 it would have installed. Then you could simply change the time back to today.

Anyway Apple renewed the certificates for the OS's and provided updated downloads. And for OS X El Capitan and macOS Sierra they decided to provide it in this manner with a .dmg and the three step process to get the installer app.

Who knows why.

Unable to install OS X El Capitan on new hard drive (Early 2008 Mac Pro)

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