Thank you very much for this!
Just to add my 2 cents: in Raspbian Jessie (mini) everything was fine except for the DHCP client which after fstab modification it was taking a life to stop waiting for an IP.
I solved editing /etc/systemd/system/dhcpcd5 this way:

changed the line

PIDFile=/run/dhcpcd.pid

into

PIDFile=/var/run/dhcpcd.pid

And now is fine.