I am currently trying to create a root account from Single User Mode on OSX Yosemite
/sbin/mount -uw /
launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
passwd
The first 2 lines appear to work fine, but after I type 'passwd' nothing comes up. Not even a propmpt to keep typing commands. I don't believe it is setting the password because anything I type is visible and even if I type the same text twice nothing happens.
When I try to run this command after the computer boots and I have logged into my account 'passwd' works as expected, it prompts me for the old password and for the new password twice.