1.Reboot the system.
2.Interrupt the boot loader countdown by pressing any key.
3.Move the cusor to the entry that needs to be booted.
4.Press e to edit the selected entry.
5.Move the cursor to the kernel command line(the line that starts with linux16).
6.Append rd.break(this will break just before control is handed from the initramfs to the actual system).
7.Press Ctrl +x to boot with changes.
8.Remount /sysroot as read-write:
mount -or emount,rw /sysroot
9.Switch into a chroot jail,where /sysroot is treated as the root of the file system tree:
chroot /sysroot
10.Set a new root password:
passwd root
11.Make sure that all unlabeled files(including /etc/shaow at this point) get relabeled during boot.
touch /.autorelabel
12.Type exit twice.The first will exit the chroot jail,and the second will exit the initramfs debug shell.
(來自別人的東西。)