How does one install Mac OS X 10.11 on an EXTERNAL DRIVE

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Level 1

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How does one install Mac OS X 10.11 on an EXTERNAL DRIVE

HELP - I’m going crazy! How does one install Mac OS X 10.11 on an EXTERNAL DRIVE (in this instance, a SanDisc Extreme PRO Portable SSD) hereafter referred to “external drive”. #1 - I formatted and created three partitions on the external drive (Mac OS Extended (Journal) and made sure GUID was selected in the formatting and partitioning process. #2 - I downloaded (from Apple) OS X El Capitan to my primary HD on my iMac (Mid-2015). I double-clicked the downloaded file to open the file within named InstallMacOSX.pkg which then displayed: "This package will run a program to determine if the software can be installed". #3 - I clicked “Continue” and then got the following message: "OS X v10.11.6 is already installed on this computer. Use the Updates page to install the 10.11 update or if you would like to download the full OS X installer click Continue".

This is where everything turns sour……….or frankly RIDICULOUS! The installer will not allow me to install this OS on a volume on the external drive because: “OS X can’t be installed in this disk. OS X isn’t installed". I KNOW IT ISN’T INSTALLED (on the external drive) because THIS IS WHAT I AM TRYING TO DO……….INSTALL IT ON THE EXTERNAL DRIVE!!!!

What am I missing here? Rather than describe some alternative thoughts I have, I am going to see of any of you kind and knowledgeable people out there can tell me exactly what I need to do to get the Mac OS X El Capitan installed on a volume on the EXTERNAL DRIVE. (Btw - I have 32.01 GB of space allocated on the volume to which I am trying to install this Mac OS.) Would greatly appreciate some expert advice………..

Posted on Aug 13, 2020 4:05 PM

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Answer 1

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Eau Rouge

Level 8

42,620 points

Aug 14, 2020 12:24 AM in response to SergeantMac

Ok calm down.

So you have the InstallMacOSX.pkg and you have double-clicked on that and got an installation window.

Read it very carefully because it says this will take 7MBs of disk space, so this should get you thinking

how come El Capitan is only 7MBs, no OS is only 7MBs, once installed they are usually 25-30GBs.

What the InstallMacOSX.pkg is actually doing is creating the Install OS X El Capitan.app

and this needs to be placed in your Applications folder, so if you get asked which disk you

want to 'install' to then it has to be your internal drive not the external drive.

Now that you have Install OS X El Capitan.app in your Applications folder (it should be 6.2GBs)

you can simply double-click on that to start the installation process.

Follow the prompts one of the windows will then ask you to select a disk where you want to install

El Capitan to, this is where you select your external disk.

The copy of the install app self deletes after installing El Capitan, so make sure you keep a copy of the InstallMacOSX.dmg

if you need it in future, or you could just make a copy of the Install OS X El Capitan.app prior to installing and moving it to

an external drive for safe keeping. It is also possible to create a bootable USB installer disk using the Install OS X El Capitan.app

in the Applications folder and the createinstallmedia command in the Terminal app.

Read the instructions here,

How to create a bootable installer for macOS – Apple Support

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Answer 2

SergeantMac Author

Level 1

53 points

Aug 14, 2020 10:36 AM in response to Eau Rouge

Yes, thanks much Eau Rouge. The thing I was missing was installing the "Install OS X El Capitan.app" into my Applications folder on my internal HD. I was hesitant to do this because I was thinking this would start to install over my existing OS on my internal HD. Since it's been many years since I have done this, I didn't realize that I would be given the choice of where to install this OS. (Btw- I noticed that somehow, along with the "Install OS X El Capitan.app", "Install macOS Sierra.app" and "Install macOS Mojave.app" were placed in my Applications folder. Hey, I'm old - what can I say..........Appreciate your thorough explanation my friend.

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How does one install Mac OS X 10.11 on an EXTERNAL DRIVE

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