I am salvaging a mid 2013 MacBook Air 11' that was discarded with a broken screen backlight due to beverage spill and missing its SSD. (I have a very tiny budget right now so I'm only spending on more expensive items when my testing shows the machine might work well.)

I got the Apple Store to test the hardware then tested the computer myself by taking about two days to install OS X from one USB 2.0 flash drive to another USB 2.0 flash drive using an external display.
It seemed to work quite well other than that it ran at about 1% the speed of a normal Mac for anything that required disk access. This made it hard to test in any depth as problems could easily be due to OS X internal timeouts.
I have now purchased a USB 3.0 external hard drive and knowing how slow USB 2.0 flash drives are to install from and to, I'm hoping to use the fast external hard drive for both, but I'm not sure whether this is possible or how.
The external drive happened to come pre-formatted for Mac with two partitions, which to seems ideal.

Jan 13, 2020 I have downloaded the El Capitan dmg file (InstallMacOSX.dmg) provided by Apple. The expanded dmg image contains the package 'InstallMacOSX.pkg' which should be run to create the El Capitan installer but fails with the following message 'This version of OS X 10.11 cannot be installed on this computer.' DVD DL, Mac OS X 10.11 El Capitan Full OS Install Reinstall Recovery Upgrade. Latest certificate (expires ). Please CHECK twice if your Mac model is compatible with this macOS!! If you are not 100% sure please check the pics or message me your mac model and year and I can tell for sure if would work or not! Make sure you have Install OS X El Capitan.app in your Application Folder 2. Select 'On an external drive' on the main MCPF window. Then, choose the disk you want to install the El Capitan installer on. Click install and prompt your password. Boot the computer you want to install El Capitan on with 'alt' held and select.

Can I just copy the contents of the El Capitan bootable installer USB to one of the partitions? I fear I may need to copy it as a drive/partition rather than as a file or folder, since it must be bootable. Does such a copy require special software?

Aug 03, 2021 Features Of Mac OS X El Capitan System Integrity Protection. How to Perform a Clean Install of OS X El Capitan. OS X El Capitan (OS X 10.11) offers two installation methods. This guide focuses on the 'clean install' method. When you install El Capitan on your current startup drive with the clean install method, you erase everything on the drive.
I need to ask the experts here without being able to experiment since I'm unable to justify the purchase price of a magsafe 2 power supply until I'm confident the machine will work well. I am able to borrow a power supply only occasionally from friends.
Yosemite Installer
I realize doing an Internet OS restore via Wi-Fi is another possibility but the Wi-Fi I have access to is both slow and behind a captive portal. So for this question I'm not pursuing that option thank you.



