This is it, you have a bootable OS X usb drive. Any mac that came preinstalled with an OS newer than El Capitan will refuse to do the conversion to the Install OS. El Capitan, this includes macs that once ran El Capitan but have been upgraded to a newer OS. From the first iso, obtained on step 3, copy BaseSystem.chunklist and BaseSystem.dmg on the thumb drive (actually, the latter might not be necessary - but it worked for me at this step and I stopped experimenting). and then create the Install OS X El Capitan.app can only be done on macs that are capable of running Mac OS X. Mount the thumb drive (you might need to apt-get install hfsprogs to mount an HFS filesystem). In my case (High Sierra 10.13.6), 4Gb stick was sufficient, even though createinstallmedia requires 8Gb. iso as well ( dmg2iso -i BaseSystem.dmg -o BaseSystem.iso)Ĭopy it to a thumb drive: dd if=BaseSystem.iso of=/dev/sdX BS=1M. iso įind BaseSystem.dmg in the mounted image. You can do it from GUI (right click, 'Open with disk image mounter') or something like mount -o loop. So, you'll need to find an alternative source.Ĭonvert. This question on apple support has all the links, but they are only accessible from OS X (if you had access to a live OS X at this point - you probably would've just used createinstallmedia already, right?). Its the easiest way to build an OS X/macOS Installer in a few. Unlike El Capitan, High Sierra only needs BaseSystem.dmg, which also has enough free space to boot - so, the process overall can be simplified a bit. Then, it proposes to build a bootable install disk and make it look as nice as possible. So, leaving it here in case somebody else will need to. Download the El Capitan installer from the App Store and then select El Capitan in Diskmaker X.

I recently had to make a High Sierra 10.13.6 bootable USB drive, and the process turned out a bit more involved that just dd-ing the dmg2img-generated ISO to a thumb drive.

Create el capitan usb installer