How to create Apple's Bootable MacOS Rescue Image from Linux

Create a Bootable MacOS Recovery USB with Linux.md

See bootableinstaller.com

How to create a Bootable MacOS Recovery USB from Linux

If your Mac is out-of-order or you otherwise cannot download macOS from the App Store, you can still create a bootable OS X recovery USB, and you can use that to create an Installer USB.

The downloads used in this process are legal and freely avaliable - including disk images directly from Apple's IT support pages, and open source utilities for extracting and converting pkg, dmg, and HFS+.

No hackery. No hackintosh-ery.

This process works for

• macOS Catalina (10.15)
• macOS Mojave (10.14)
• macOS High Sierra (10.13)
• macOS Sierra (10.12)
• OS X El Capitan (10.11)
• OS X Yosemite (10.11)

In all cases you should first download the El Capitan Installer, as a direct download from Apple (no App Store).

The OS X Yosemite and macOS Sierra images should also work, but you might have trouble getting macOS Sierra to boot in VirtualBox.

Recovery USB vs Installer USB

This is a 3-step process:

1. Create a Recovery ISO with Linux
2. Create an El Capitan Installer ISO with VirtualBox from the Recovery image
3. Create other Installer USBs from El Capitan in VirtualBox

Create the Recovery ISO

The Apple download contains a recovery image called BaseSystem.dmg which needs to be copied to a correctly partitions and formatted recovery USB or ISO.

1. Download the OS X El Capitan installer
   • Note for Windows users running Linux from VirtualBox:
     • you already downloaded InstallOSX.dmg to your USB drive, so skip this step
   • Visit Apple's official "How to upgrade to El Capitan" documentation
   • Click "Download OS X El Capitan" in Step 4
   • InstallOSX.dmg will be about 6GB in your Downloads folder
2. Install HFS+ tools for Linux
   • See install-mac-tools.sh below
   • Note for Windows users running Linux from VirtualBox:
     • choose to download to your USB drive, NOT Downloads
     • run the script from your USB drive, NOT Downloads
   • Right-Click on the view Raw link, choose Save as, and select the Downloads folder
   • Open a Terminal and run bash install-mac-tools.sh from the Downloads folder

   pushd ~/Downloads
   bash install-mac-tools.sh

3. Create el-capitan-recue.iso
   • See linux-create-bootable-macos-recovery-image.sh below
   • Note for Windows users running Linux from VirtualBox:
     • choose to download to your USB drive, NOT Downloads
     • run the script from your USB drive, NOT Downloads
   • Right-Click on the view Raw link, choose Save as, and select the Downloads folder
   • Open a Terminal and run bash linux-create-bootable-macos-recovery-image.sh from the Downloads folder

   pushd ~/Downloads
   bash linux-create-bootable-macos-recovery-image.sh

You can of course run each command of the scripts by hand, but since it's deeply nested (.dmg containing a .pkg containing another .dmg with another .dmg inside), and requires loopback mounts, it's a rather tedious and mundane process.

Boot the Recovery ISO

You will need a 32GB+ USB drive, ExFAT formatted.

You should copy ElCapitanInstallESD.dmg from Downloads to your USB drive.

install-mac-tools.sh

########################################################################################################################
#                                                bootableinstaller.com                                                 #
########################################################################################################################

set -e
set -u
set -x

# Install HFS+ and dmg dependencies
if ! [ $(command -v mkfs.hfsplus) ] || ! [ $(command -v dmg2img) ]; then
	# Note: hfsplus and hfsutils are old and not necessary
	# Note: mac-fdisk (mac-fdisk-cross) is useful for debugging, but not required
	sudo apt install -y hfsprogs dmg2img
fi

# Install xar
if ! [ -f "xar/xar/src/xar" ]; then
        echo "Installing XAR from https://github.com/mackyle/xar.."

        sudo apt install -y build-essential autoconf
        sudo apt install -y libxml2-dev libssl-dev git
        rm -rf xar/
        git clone https://github.com/mackyle/xar
        pushd xar/xar
                sed -i.bak 's/OpenSSL_add_all_ciphers/OPENSSL_init_crypto/g' configure.ac
                ./autogen.sh --prefix=/usr/local
		make
		sudo make install
        popd
fi

linux-create-bootable-macos-recovery-image.sh

########################################################################################################################
#                                                bootableinstaller.com                                                 #
########################################################################################################################

# Put bash in "strict mode"
set -u
set -e

if [ -f "./el-capitan-rescue.iso" ]; then
  echo "'el-capitan-rescue.iso' already exists"
  exit 0
fi

# Show commands as they are executed
set -x

my_installesd="./ElCapitanInstallESD.img"
if ! [ -f "./InstallESD.img" ]; then
    my_installesd="./InstallESD.img"
fi

if ! [ -f "$my_installesd" ]; then
        if ! [ -f "./InstallMacOSX/InstallMacOSX.pkg/InstallESD.dmg" ]; then
                if ! [ -f "./InstallMacOSX.img" ]; then
                        if ! [ -f "./InstallMacOSX.dmg" ]; then
                                echo "Error: 'InstallMacOSX.dmg' doest not exist."
                                echo "    Go to https://support.apple.com/en-us/HT206886"
                                echo "    In step 4 click 'Download OS X El Capitan'"
                        fi

                        # decompresses into a dd-like image
                        dmg2img InstallMacOSX.dmg -o ./InstallMacOSX.img
                        chmod a-w ./InstallMacOSX.img
                        # rm InstallMacOSX.dmg
                fi

		my_fullosx=$(sudo losetup --list | (grep InstallMacOSX.img || true))
                if ! [ -f "/mnt/InstallMacOSX/InstallMacOSX.pkg" ]; then
                        my_fullosx=$(sudo losetup --partscan --show --find InstallMacOSX.img)
                        echo "$my_fullosx"
                        sudo fdisk -l "$my_fullosx"
                        ls -l "$my_fullosx"p*

                        sudo partprobe $my_fullosx
                        sudo mkdir -p /mnt/InstallMacOSX
                        sudo mount "$my_fullosx"p2 -o ro,noatime /mnt/InstallMacOSX
                fi

                echo "Extracting /mnt/InstallMacOSX/InstallMacOSX.pkg"
                mkdir -p ./InstallMacOSX.tmp.d/
                pushd ./InstallMacOSX.tmp.d/
                        #LD_LIBRARY_PATH=../xar/xar/lib ../xar/xar/src/xar -xvf /mnt/InstallMacOSX/InstallMacOSX.pkg
			# TODO maybe use pzip / 7zip instead?
                        xar -xvf /mnt/InstallMacOSX/InstallMacOSX.pkg
                popd
                mv ./InstallMacOSX.tmp.d ./InstallMacOSX

                sudo umount /mnt/InstallMacOSX
                sudo losetup -d "$my_fullosx"
        fi

	if ! [ -f "./ElCapitanInstallESD.img" ]; then
		dmg2img ./InstallMacOSX/InstallMacOSX.pkg/InstallESD.dmg -o ./ElCapitanInstallESD.img
		chmod a-w ./ElCapitanInstallESD.img
	fi
        my_installesd=./ElCapitanInstallESD.img

        # TODO it's now safe to remove the big fat InstallMacOSX.*mg and ./InstallMacOSX/
fi

my_esd=$(sudo losetup --list | (grep InstallESD.img || true) | cut -d' ' -f1)
if ! [ -f "/mnt/InstallESD/BaseSystem.dmg" ]; then
        my_esd=$(sudo losetup --partscan --show --find "$my_installesd")
        echo "$my_esd"
        sudo fdisk -l "$my_esd"
        ls -l "$my_esd"p*

        sudo partprobe $my_esd
        sudo mkdir -p /mnt/InstallESD
        sudo mount "$my_esd"p2 -o ro,noatime /mnt/InstallESD
fi

if ! [ -f "./BaseSystem.img" ]; then
        dmg2img /mnt/InstallESD/BaseSystem.dmg -o ./BaseSystem.img
        chmod a-w ./BaseSystem.img
fi

my_base=$(sudo losetup --list | grep BaseSystem.img | cut -d' ' -f1)
if [ -z "$my_base" ]; then
        my_base=$(sudo losetup --partscan --show --find ./BaseSystem.img)
        echo "$my_base"
        sudo fdisk -l "$my_base"
        ls -l "$my_base"p*

        sudo partprobe $my_base
fi

my_empty=$(ls empty*img.bz2 | sort | head -1)
cp -rp "$my_empty" el-capitan-rescue.dd.img.bz2
bunzip2 el-capitan-rescue.dd.img.bz2

my_dd=$(sudo losetup --partscan --show --find el-capitan-rescue.dd.img)
echo "$my_dd"
sudo mac-fdisk -l "$my_dd"
ls -l "$my_dd"p*

sudo dd if="$my_base"p1 of="$my_dd"p2 bs=128M status=progress

sudo losetup -d "$my_dd"
mv el-capitan-rescue.dd.img el-capitan-rescue.iso

sudo umount /mnt/InstallESD
sudo losetup -d "$my_esd"

chmod a-w ./el-capitan-rescue.iso
echo "el-capitan-rescue.iso"