I am trying to make a bootable disk for El Capitan using Diskmaker X5 (I have a MacPro 2010 with OX X 10.5). This does not succeed. The comment is 'no valid sudoers sources found, quitting'. After that nothing happens.
What does this message mean? How can I get 'valid shudders'?
This is the method I used comes from ARS Technica and works great. You need to label the USB drive as Untitled. Make sure there is a copy of El Capital in the Applications folder you may have to download it again because it deletes after the inital install.
"If you don't want to use Diskmaker X, Apple has actually included a terminal command that can create an install disk for you. Assuming that you have the OS X El Capitan installer in your Applications folder and you have a Mac OS X Extended (Journaled)-formatted USB drive named "Untitled" mounted on the system, you can create an El Capitan install drive by typing the following command into the Terminal.
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
The command will erase the disk and copy the install files over. Give it some time, and your volume will soon be loaded up with not just the OS X installer but also an external recovery partition that may come in handy if your hard drive dies and you're away from an Internet connection".