You can reinit the password :
1.stop mysql
/etc/init.d/mysql stop
2.start mysql safe :
mysqld_safe --skip-grant-tables &
3.connect to mysql
mysql -u root
4.change the password
mysql> use mysql;
mysql> update user set password=PASSWORD(”YOUR_PASSWORD”) where user=’root’;
mysql> flush privileges;
mysql> quit
5.stop mysql
/etc/init.d/mysql stop
6.start mysql
/etc/init.d/mysql start
Then you can connect to mysql with login root and the new password.
mysqld_safe
resulted in SOCKET file errors. I was able to fix these by manually making the directory and then giving it to the mysql user. See this answer. (Mint 18, mysql 5.7) – Deleet Sep 20 '17 at 10:33