How to make bootable El Capitan ISO image
After downloading El Capitan installer app from Apple Store, you can either upgrade your existing MAC OS to El Capitan, make a bootable USB using \”createinstlallmedia\” from the package, or you can make a bootable ISO image to use either with virtual CDROM or to burn your own installation DVD. I will show you how to create a bootable ISO image of the El Capitan.
First, we need to mount InstallESD.dmg from /Applications/Install El Capitan.app
$ hdiutil attach "/Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg" -noverify -nobrowse -mountpoint /Volumes/esd /dev/disk5 GUID_partition_scheme\n/dev/disk5s1 EFI\n/dev/disk5s2 Apple_HFS /Volumes/esd
-noverify switch speeds up mounting process and -nobrowse prevents Finder poping up windows after mount
Now we will create a placeholder for our ISO image:
$ hdiutil create -o ElCapitan3.cdr -size 7613m -layout SPUD -fs HFS+J\n..................................................................... created: /Users/amnesia/ElCapitan.cdr.dmg
After the placeholder is created, we need to mount it:
$ hdiutil attach ElCapitan3.cdr.dmg -noverify -nobrowse -mountpoint /Volumes/iso /dev/disk6 Apple_partition_scheme /dev/disk6s1 Apple_partition_map /dev/disk6s2 Apple_HFS /Volumes/iso
Now use asr tool to populate ISO image:
$ asr restore -source /Volumes/esd/BaseSystem.dmg -target /Volumes/iso -noprompt -noverify -erase Validating target...done\nValidating source...done\nRetrieving scan information...done Validating sizes...done\nRestoring ....10....20....30....40....50....60....70....80....90....100 Remounting target volume...done
\nasr tool will automatically create new mountpoint /Volumes/OS X Base System. We need to place some files in til directory:\n\nFirst remove invalid link:\n
$ rm /Volumes/OS\\ X\\ Base\\ System/System/Installation/Packages
Now we will copy proper directory that contains package files. This is done from the ESD media:
$ cp -rp /Volumes/esd/Packages /Volumes/OS\ X\ Base\ System/System/Installation
\nThe next step is to copy some additional dependencies:\n
$ cp -rp /Volumes/esd/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/ $ cp -rp /Volumes/esd/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/
Now unmount the unnecessary volumes:
$ hdiutil detach /Volumes/esd/ "disk5" unmounted. "disk5" ejected. bash-3.2# hdiutil detach /Volumes/OS\ X\ Base\ System/ "disk6" unmounted. "disk6" ejected.
Now we need to convert our ISO to UDTO format:
$ hdiutil convert ElCapitan3.cdr.dmg -format UDTO -o ElCapitan.iso Reading Driver Descriptor Map (DDM : 0)… Reading Apple (Apple_partition_map : 1)… Reading disk image (Apple_HFS : 2)… ......................................................................... Elapsed Time: 50.898s Speed: 149.6Mbytes/sec Savings: 0.0% created: /Users/amnesia/ElCapitan.iso.cdr
Rename ElCapitan.iso.cdr to ElCapitan.iso and use it as needed