How to boot a ppc64el machine:
Petitboot is a platform independent bootloader based on the Linux kexec. Petitboot supports loading kernel, initrd and device tree files from any Linux mountable filesystem, plus can load files from the network using the FTP, SFTP, TFTP, NFS, HTTP and HTTPS protocols. Petitboot can boot any operating system that includes kexec boot support.
Petitboot looks for bootloader configuration files on mountable devices in the system, and can also be configured to use boot information from a DHCP server.