sys-unconfig is a shell script to reconfigure the system upon next boot .. The man page description is more than enough to know what parameters are reconfigured from next boot..
sys-unconfig provides a simple method of reconfiguring a system in a new environment. Upon executing sys-unconfig will halt your system,
and run the following configuration programs at boot: passwd (to change the root password), netconfig, timeconfig, kbdconfig, authconfig,
A file ( hidden) called “unconfigured” will be present inside “/” when you run sys-unconfig command . The presence of this file will cause /etc/rc.d/rc.sysinit to run the programs mentioned above.
Please note that, running “sys-unconfig” command will cause the system to go down immediately..
Also, all persistent rules will be deleted from /etc/udev/rules.d/.