1. Stop mysql service

systemct stop mysqld

1. add this line to /etc/my.cnf

skip-grant-tables

1. start mysql service

systemct start mysqld

1. Log in like root (whitout password)

 mysql -u root

1. change root password

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
 
Database changed
mysql> update user set authentication_string=password('Isr_1234') where user='root';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql> exit

1. comment line from /etc/mycnf
2. restart mysql service

systemct; restart mysqld