Guide to install old macOSX versions - bootable USB key

This guide is base on macOSX Yosemite but works on others versions.

Prepare USB key

Launch Disk Utility, choose the USB key and Erase; set:

• Name, to Untitled
• Format, to Mac OS Extended (Journaled)

Get old versions of macOS

Get old version from here:

• https://support.apple.com/en-us/HT211683

this will download InstallMacOSX.pkg file.

Extracting the Installer

Create a working dir:

cd ~/Desktop
mkdir -p MacInstall/extract

Mount the InstallMacOSX.dmg (doubble click) and then:

cd ~/Desktop/MacInstall
cp /Volumes/Install\ OS\ X/InstallMacOSX.pkg .

Create app

cd ~/Desktop/MacInstall/extract
xar -xf ~/Desktop/MacInstall/InstallMacOSX.pkg
cd InstallMacOSX.pkg
tar xvzf Payload
mv InstallESD.dmg Install\ OS\ X\ Yosemite.app/Contents/SharedSupport
mv Install\ OS\ X\ Yosemite.app /Applications

Create USB bootable key

sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite.app

Use the bootable installer (Intell processor)

• Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
• Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
• Release the Option key when you see a dark screen showing your bootable volumes.
• Select the volume containing the bootable installer. Then click the up arrow or press Return.

!!! NOTE !!! - If you are receiving the message:

1 solution

before to start the installer, in the first install page go to Utilities -> Terminal and set the the date using the command data with options:

MM - 2 digit month  01 - 12
DD - 2 digit date   01 - 31
HH - 2 digit hour   01 - 24
mm - 2 digit minute 01 - 59
YY - 2 digit year   > 15

for example date 24-Nov-2021 11:11:00:

-bash-3.2# date 1124101121
Wed Nov 24 10:11:00 PST 2021
-bash-3.2#

once that is done go through the install normally.

2 solution

try to bypass the security check in Utilities -> Terminal:

-bash-3.2# installer -pkg /Volumes/Mac\ OS\ X\ Install\ DVD/Packages/OSInstall. mpkg -target /Volumes/Macintosh\ HD/

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(c) 2021 Valentino Lauciani vlauciani[at]gmail.com