Create bootable OS X 10.11 installation media from macOS 26

The following are steps that worked for me, to create a bootable USB copy of the OS X 10.11 installer while running macOS 26. This procedure was adapted from a guide I found posted in 2015.

I suspect this process would be similar for other versions that are distributed as disk images (10.7 through 10.12), but I haven’t tested any except 10.11.

  1. Download the disk image from Apple’s support page. This will download a file called InstallMacOSX.dmg that’s about 6.2 GB.
  2. Open InstallMacOSX.dmg to mount a volume called Install OS X.
  3. Using Pacifist, open the InstallMacOSX.pkg package contained within the Install OS X volume.
  4. Under the Package Resources tab in Pacifist, expand InstallMacOSX Contents and the second-level InstallMacOSX Contents to find a file called InstallESD.dmg. Copy InstallESD.dmg to your hard drive.
  5. Quit Pacifist, eject the Install OS X volume, and delete InstallMacOSX.dmg.
  6. Open InstallESD.dmg to mount a volume called OS X Install ESD.
  7. In Disk Utility, create a new Blank Image, with the following parameters:
    • Save As: Bootable_OS_X_Installer_10_11 (or whatever you prefer)
    • Name: OS X Base System
    • Size: 7600 MB
    • Format: Mac OS Extended (Journaled)
    • Encryption: None
    • Partitions: Apple Partition Map
    • Image Format: DVD/CD master (Be aware when you select this, the Size may change to 100 MB. Make sure the size is correct before clicking Save.)
  8. In Disk Utility, the newly-created blank image should already be mounted and listed as OS X Base System (if not, open Bootable_OS_X_Installer_10_11.dvdr.cdr to mount it). Select the OS X Base System volume, and choose Restore, and then for Restore from… select Image…. Within the root of the OS X Install ESD volume, select BaseSystem.dmg and proceed with restoring from that image. (You may need to show hidden files to see BaseSystem.dmg; you can do that with Command + Shift + ..)
  9. Within the OS X Base System volume, you will now see files present after there restore (Applications, Install OS X El Capitan, System, etc). Open the System folder, and then open the Installation folder. Delete the alias called Packages.
  10. Copy the Packages folder from the root of the OS X Install ESD volume into /System/Installation on OS X Base System (i.e., replace the alias you just deleted with the folder). This folder is over 5 GB, so it may take several seconds.
  11. Also copy both BaseSystem.chunklist and BaseSystem.dmg from the root of the OS X Install ESD volume (they will likely be hidden) to the root of the OS X Base System volume. The files should now appear next to things like Applications, Install OS X El Capitan, System, etc.
  12. Eject the OS X Install ESD volume, and delete InstallESD.dmg.
  13. Rename the OS X Base System volume to something more descriptive, like Install Mac OS X El Capitan, and eject that volume.
  14. Rename Bootable_OS_X_Installer_10_11.dvdr.cdr to Bootable_OS_X_Installer_10_11.iso.
  15. Use Etcher to write the ISO to a USB drive. Ignore the warning about the image missing a partition table.
  16. Delete Bootable_OS_X_Installer_10_11.iso if you no longer need it.