Installing Mac OS from external hard drive


I have an old MacBook pro (late 2011). I have tried to install the OS via the internet but keep getting errors. I have a second hard drive that has Sierra installed on it. I would like to use this second drive to install the OS on the first machine. There is one thing however. I want to make sure that only the OS is copied and installed on the MacBook pro. I don't want any documents to be brought across. I have the tools to connect the drive via the USB port. Any suggestions on how to perform this?


What you need is the OS installer (not the OS installed on a drive) to do this. You can download the installer to an external drive or flash drive. Then attach the drive with the installer to your MacBook via USB to do the install.

Now the question is what are the errors you are getting? Is there an OS already installed on the MacBook? If not, can you start up the MacBook using that external drive that has Sierra installed on it?

You can get Sierra install from here -
Scroll down for the older OS links.
Thanks for the response. The hard drive is empty, no OS on it. While booting up, I pressed the command key and 'R' for recovery over the internet. I attempted this several times, at least four. The error stated something about download error. I need to get this done as soon as possible which us is why I figured I could use the other drive connected via USB to install the OS. I already know that the MacBook is not able to run the only OS available on the web.

So the question remains, can I install from other drive without loading the documents?

You need to start up the MacBook from the external drive, download the OS installer on the other drive, then use Disk Utility on the MacBook drive to format, then you can install.
Just make sure when you open the installer that you select the MacBook's internal drive.

When you use the installer, it will not copy the documents, apps, etc.
Create a macOS Sierra Boot Install Drive

● Connect the USB drive to your Mac

● Rename it as “SierraBootInstall“

● Go to /Applications/Utilities/ >> Search Terminal and open it

● Into the Terminal, add the following command syntax -

sudo /Applications/Install\ macOS\ –volume /Volumes/SierraBootInstall –applicationpath /Applications/Install\ macOS\ –nointeraction

● Double-check it and Confirm to press the return key

● Now Enter the Admin Password into Terminal

● Process Progress will take place and will display done on completion.

● Quit Terminal, when you see this message - The macOS Sierra installer process is complete. The macOS Sierra USB is ready for use.

Reinstall macOS Sierra from USB-

● Connection the macOS Sierra boot drive to your Mac

● Attempt Mac Reboot and hold the OPTION key

● From the Boot Menu Options, select “Install macOS Sierra“

● Restart your Mac Successfully.

Source Link -
I'm pretty sure if you use the listed terminal command, as posted, it will fail with an error.
Be careful that each leading dash is actually a double-dash - such as "--volume"
The command, as listed MIGHT have double-dashes, but it is not visually apparent from the article. Won't work without that being correct.