Mysql 에러 : ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

문제점 

Mysql 로그인시 다음과 같은 에러

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) 

비밀번호 재설정 하려고 했으나 아래와 같은 증상으로 안됨

Server is running

$ mysql -u root
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

Stop server

$ sudo /etc/init.d/mysql stop
[ ok ] Stopping mysql (via systemctl): mysql.service.

Trying to start with --skip-grant-tables

sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking &
[1] 9856

Connect with no password

$ mysql -u root
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
[1]+  Exit 1                  sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking

I also tried to start with mysql_safe (error.log is empty)

sudo mysqld_safe --skip-grant-tables
2017-02-01T16:33:31.382105Z mysqld_safe Logging to syslog.
2017-02-01T16:33:31.383942Z mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-02-01T16:33:31.386058Z mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-02-01T16:33:31.388009Z mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists.

해결법

Start server

$ sudo service mysql start

Go to sock folder

$ cd /var/run

Back the sock

$ sudo cp -rp ./mysqld ./mysqld.bak

Stop server

$ sudo service mysql stop

Restore the sock

$ sudo mv ./mysqld.bak ./mysqld

Start mysqld_safe

$ sudo mysqld_safe --skip-grant-tables --skip-networking &

Init mysql shell

mysql -u root

Change password

FLUSH PRIVILEGES;

SET PASSWORD FOR root@'localhost' = PASSWORD('my_new_password');

출처 : https://stackoverflow.com/questions/41984956/cant-reset-root-password-with-skip-grant-tables-on-ubuntu-16/41987711