Sometimes you need to reset root password from a Centos 7 system.
Here I will show an easy way, not the only one.
First you’ll need access to grub boot screen, if system it’s running you can send an Ctrl+Alt+Supr key combination
If we edit all correctly we will have a shell in emergency mode
mount -o remount,rw /sysroot
afther this we will do a chroot in this dir to access to all commands
now we can change root password executing
finally we need to exit from chroot
and reboot our system to make a normal boot
now you should have root access using edited password