From Fedora Project Wiki
Reporting
Debugging
rdinitdebug
set -x for the dracut shell
rdbreak=[pre-udev|pre-mount|mount|pre-pivot|]
drop the shell on defined breakpoint
rdudevinfo
set udev to loglevel info
rdudevdebug
set udev to loglevel debug
rdnetdebug
debug network scripts in dracut