Getting 10.11 to work on older macs

I had an older mac and needed to have a Mac OS X 10.11 installed on it, it would not run anything newer. For the purposes of this explanation I am assuming you have access to a slightly newer Mac as well, e.g. 2-5 years newer than the target machine.

Step 1. get the installer DMG. Open it when it is finished downloading.

Step 2. Install on your own internal hard drive (run the installer and choose your own machine as the target). This creates the installer application in /Applications (even if your OS is newer). This part is not obvious, and surprisingly it doesn't tell you that your machine is too new.

Step 3. Get Etcher from https://etcher.io

Step 4. Attach an external hard drive. Make sure it's empty and formatted HFS+ (use Disk Utility which is in the Utilities folder in your Applications folder). You click on the hardware drive shown on the left panel, NOT the partition. Important: tell it to use a GUID partition scheme (popup menu in the centre of the righthand panel). This SHOULD create an invisible EFI partition with firmware for your machine but in practice it may just make the partition and won't show you that it exists. Yes, even if you click the hardware drive icon in disk utility and choose the "partition" command, it still doesn't show you the EFI partition.

Step 5. Open Etcher and set the SOURCE to the mounted disk image that you downloaded in step 1. Set the target to the attached external hard drive. Instruct it to copy the image disk to the external disk. Note that if the external disk is not empty it will be erased.

Step 6. Copy the application from your internal hard drive's applications folder (step 2) to the new hard drive copy (of the DMG made in step 5).

Step 7Get clover configurator. This part is totally not obvious. Open the app and look for the commands on the lefthand panel. One of them is to "mount EFI partition". Choose the newly created hard disk and then choose "mount EFI partition." EFI is an invisible partition that contains (or should contain) Mac firmware. Clover Configurator lets you attach invisible partitions, basically (amongst other things). This will attach the external drive's EFI partition and mount it on your desktop.

Step 8. Mount your own boot partition's EFI partition as well, and open it. Inside is a folder called APPLE. Copy that to the other EFI partition discovered in step 7, if it is empty. (ONLY if it is empty, ie does not have the APPLE folder). If you fail to do step 8, the hard disk won't be bootable. Really. Once you're done with this, eject the partitions from the external disk and detach that drive.

Step 9. Attach the external hard disk to the machine which is to receive 10.11.

Step 10. Boot.

Step 11. It will come up with the installer screen. Don't use it. It will not work. The date is too new, and the certificate issued by Apple with the software is invalid. You have to go to the Tools menu and open the terminal and set the computer's date to about 2016, which is when 10.11 was current. The error is "This copy of the Install OS X El Capitan application can't be verified. It may have been corrupted or tampered with during downloading"To fix this, type:

 date 0101010116 

This sets the date of the machine to 1 January, 2016 so that the installer still thinks that it is valid. 

Try repeat Step 11 and see if it lets you install to the hard disk. If it gives the SAME error, then you have to use the commandline (step 12).

Step 12. This step is if Step 11 fails. Type the following into the same terminal, as a single command-line (no enter key, except at the end).

installer -verbose -pkg /Volumes/Mac\ OS\ X\ Install\ DVD/Packages/OSInstall.mpkg -target /Volumes/"XXX"

...where XXX is the name of the disk you're installing to. If the disk has spaces in its name, you need quotemarks as shown. If the disk does not have spaces in its name, then you do not need quotemarks. This process may take 2-3 hours to complete, so be patient. It will give a hashmark (#) as it progresses. If you are impatient, you can background this command by hitting ctrl-z and then typing

bg

followed by the enter key.

You can then periodically type:

df -h | grep G

to see the drive filling up. It should take about 15-20GB to install (the installer is 6GB but it is compressed).

Step 13. When the command indicates that it is finished installing, shut the machine down and detach the external installer drive. The target machine should now boot properly.

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