How to install OSX in VirtualBox

vbox_osx_howto.txt

* On a Mac/other OSX VM, get El Capitan in AppStore
* Similar for High Sierra, see https://gist.github.com/agentsim/00cc38c693e7d0e1b36a2080870d955b#gistcomment-2214881
  for the changed script.
  You might have to reboot your Mac after Downloading High Sierra in the AppStore,
  in case the first hdiutil attach ... step fails.
* (Create install ISO with following script:)

	#!/bin/bash
	
	# Mount the Installer image
	hdiutil attach /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
	
	# Create El Capitan sparseimage of 7316mb with a Single Partition - Apple Partition Map
	hdiutil create -o /tmp/ElCapitan -size 7316m -layout SPUD -fs HFS+J -type SPARSE
	
	# Mount the El Capitan sparseimage
	hdiutil attach /tmp/ElCapitan.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build
	
	# Restore the Base System into the El Capitan Blank sparseimage
	asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
	
	# Remove Packages link and replace with actual files
	rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages
	cp -rp /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/
	
	# Copy El Capitan installer dependencies
	cp -rp /Volumes/install_app/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
	cp -rp /Volumes/install_app/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg
	
	# Unmount the installer image
	hdiutil detach /Volumes/install_app
	
	# Unmount the Base System image
	hdiutil detach /Volumes/OS\ X\ Base\ System/
	
	# Optimise Sparseimage Size
	hdiutil compact /tmp/ElCapitan.sparseimage
	hdiutil resize -size min /tmp/ElCapitan.sparseimage
	
	# Convert the ElCapitan spareseimage to ISO/CD master
	hdiutil convert /tmp/ElCapitan.sparseimage -format UDTO -o /tmp/ElCapitan.iso
	
	# Rename the ElCapitan ISO image and move it to the desktop
	mv /tmp/ElCapitan.iso.cdr ~/Desktop/'EC 10.11.0.iso'
	
	# Delete ElCapitan.sparseimage file
	rm -f /tmp/ElCapitan.sparseimage

  ###### EOF ######

* Copy resulting ISO to VM host
* New VM, OSX El Capitan (or whatever), ...
* Tell the VM it's a Mac (replace "El_Capitan" with your VM name):
	VBoxManage modifyvm "El_Capitan" --cpuidset 00000001 000306a9 04100800 7fbae3ff bfebfbff
	VBoxManage modifyvm "Your Virtual Machine Name" --cpu-profile "Intel Core i7-6700K" // maybe line before is not needed?
	VBoxManage setextradata "El_Capitan" "VBoxInternal/Devices/efi/0/Config/DmiSystemProduct" "MacBookPro11,3"
	VBoxManage setextradata "El_Capitan" "VBoxInternal/Devices/efi/0/Config/DmiSystemVersion" "1.0"
	VBoxManage setextradata "El_Capitan" "VBoxInternal/Devices/efi/0/Config/DmiBoardProduct" "Mac-2BD1B31983FE1663"
	VBoxManage setextradata "El_Capitan" "VBoxInternal/Devices/smc/0/Config/DeviceKey" "ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc"
	VBoxManage setextradata "El_Capitan" "VBoxInternal/Devices/smc/0/Config/GetKeyFromRealSMC" 1
	
* Mount ISO, install (Create Partition with Utilities Menu -> Disk Utility -> Erase)
	
* Set resolution via VM's EFI:
	VBoxManage setextradata "El_Capitan" "VBoxInternal2/EfiGopMode" <N>
	// <N> can be one of 0,1,2,3,4,5 for 640x480, 800x600, 1024x768, 1280x1024, 1440x900, 1920x1200
  - Apparently in VirtualBox 5.2.0 and newer you can set a custom resolution, like
        VBoxManage setextradata "El_Capitan" "VBoxInternal2/EfiGraphicsResolution" "1920x1080"

For El Capitan (and probably other older OSX versions), installation will fail nowadays because their
package signatures expired ("No packages were eligible for install").
Workaround: Reset date to 2018 or something, can be done in installer:
Utilities Menu -> Terminal, there use the date command, like
# date 010120302018
Then finish the installation as usual