In /usr/share/initramfs-tools/hooks/biosdevname, the line:
cp -p /etc/udev/rules.d/$RUlES $DESTDIR/lib/udev/rules.d/
the variable $RUlES needs to be changed to $RULES (capital "L", not lower case).
Currently, update-initramfs will fail if you have a custom /etc/udev/rules.d/71-biosdevname.rules file.
This is in Ubuntu Server 14.04.3 LTS.
In /usr/share/ initramfs- tools/hooks/ biosdevname, the line:
cp -p /etc/udev/ rules.d/ $RUlES $DESTDIR/ lib/udev/ rules.d/
the variable $RUlES needs to be changed to $RULES (capital "L", not lower case).
Currently, update-initramfs will fail if you have a custom /etc/udev/ rules.d/ 71-biosdevname. rules file.
This is in Ubuntu Server 14.04.3 LTS.