After upgrading my Ubuntu server from 12.04 to 14.04 this morning, I tried to restart php5-fpm and got this error:
Unknown job: php5-fpm
It is a Ubuntu's bug: https://bugs.launchpad.net/ubuntu/+source/php5/+bug/1272788/
One workaround that works for me is:
Create /etc/init/php5-fpm.override file with the single line "reload signal USR2" in it.