Reinstall MySQL and Preserve All MySQL Grants and Users

read this :
I am not sure if  pt-show-grants tools will migrate all user login  + thier password and all user DB grants all together.

what if source DB server do not have percona toolkit install, do you know if this tools can scan remove DB and save the output locally ?

Please suggest.

You could use mysqlpump.
 mysqlpump --exclude-databases=% --exclude-triggers=% --users > users.dmp ( see )

so by this, all password and permission grant all can be restore ?
then  users.dmp is the sql script for us to restore by :
 mysql  -u <user account> -p < users.dmp
when I tried, it seems that if there is already an existing SAME account already there it can’t recreate, right?

how to make it works then.

I found a link say that this is going to work but I am not sure, someone said no as it broke things:
mysqldump -u root -p mysql user > user_table_dump.sql
is that right?