My understanding is that using $root_device is safer, since it comes from find_root_device which also parses fstab but is more robust than the awk command (+ handles LABEL and UUID).
Strangely enough kopt_2_6, differently from kopt, did already use $root_device as opposed to the awk code.
Note that when not on a loopinstallation, I am setting:
default_ kopt="root= $root_device ro"
When in the original code it used to be
kopt="root=$(awk '$2 == "/" {print $1}' /etc/fstab) ro"
My understanding is that using $root_device is safer, since it comes from find_root_device which also parses fstab but is more robust than the awk command (+ handles LABEL and UUID).
Strangely enough kopt_2_6, differently from kopt, did already use $root_device as opposed to the awk code.