I'm trying to install Ubuntu 15.04 on my Mac. The current operating system is El Capitan. I have made the flash disk and I can have Ubuntu with the flash drive but when I try installing it, it doesn't give me the option of "install Ubuntu along Mac OSX". It actually says that no operating system has been found. Can anyone help me fixing this? Thanks. BTW I've made the flash drive with the manual approach so I don't have the rEFIT or any other software.
Install rEFInd. rEFInd is a boot manager that will allow you to choose between Mac OS X, Linux, Windows, and other operating systems when you boot your computer.
Partition your Mac.
Boot and install Linux.