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