Normally you can’t obtain bootable media of macOS. OS X was a different story, but also you had to pay for those versions. As an owner of a MacBook Pro, it’s slightly unsettling that I wouldn’t necessarily be able to plug in a bootable USB or insert a DVD with the macOS installer image in the event that I needed to re-install my OS because my SSD ate the dust, or something.
This guide will also be useful for those who can run Virtual Machines of macOS in environments like VirtualBox etc.
Overview of how to create a bootable macOS 10.13 High Sierra ISO image:
- Download macOS from app store
- Open Terminal
- Run commands
- Rename to .ISO
Click this link to open the macOS High Sierra download in the App Store
Especially if you’ve already upgraded to high sierra and deleted the installer data (with CleanMyMac etc) you will need to download this again before proceeding with this article.
Run commands in Terminal
Run these commands one at a time
hdiutil create -o /tmp/HighSierra.cdr -size 5130m -layout SPUD -fs HFS+J
hdiutil attach /tmp/HighSierra.cdr.dmg -noverify -mountpoint /Volumes/install_build
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/install_build
mv /tmp/HighSierra.cdr.dmg ~/Desktop/InstallSystem.dmg
hdiutil detach /Volumes/Install\ macOS\ High\ Sierra
hdiutil convert ~/Desktop/InstallSystem.dmg -format UDTO -o ~/Desktop/HighSierra.iso
Here are some of my outputs for you to review (after the first three commands)
The resulting file on my desktop is almost ready to use.
Rename the file, removing
.cdr from the end. Confirm by clicking “Use .iso”
The resulting ISO can be used to create bootable USBs, DVDs, install VMs, or simply to archive for your backups “just in case”.