MySQL登录报错ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
环境：CentOS 6.5 64bit
一、安装mysqld（mysql-server）
查看系统中是否已经安装mysqld
[root@localhost ~]# rpm -e mysql-server
error: package mysql-server is not installed先通过如下命令查看yum上提供下载的mysql版本信息
[root@localhost ~]# yum list | grep mysql
mysql-libs.x86_64 5.1.73-8.el6_8 @base
php-mysql.x86_64 5.3.3-49.el6 @base
apr-util-mysql.x86_64 1.3.9-3.el6_0.1 base
bacula-director-mysql.x86_64 5.0.0-13.el6 base
bacula-storage-mysql.x86_64 5.0.0-13.el6 base
dovecot-mysql.x86_64 1:2.0.9-22.el6 base
freeradius-mysql.x86_64 2.2.6-7.el6_9 updates
libdbi-dbd-mysql.x86_64 0.8.3-5.1.el6 base
mod_auth_mysql.x86_64 1:3.0.0-11.el6_0.1 base
mod_auth_mysql-debuginfo.x86_64 1:3.0.0-11.el6_0.1 debug
mysql.x86_64 5.1.73-8.el6_8 base
mysql-bench.x86_64 5.1.73-8.el6_8 base
mysql-connector-java.noarch 1:5.1.17-6.el6 base
mysql-connector-odbc.x86_64 5.1.5r1144-7.el6 base
mysql-debuginfo.x86_64 5.1.73-8.el6_8 debug
mysql-devel.i686 5.1.73-8.el6_8 base
mysql-devel.x86_64 5.1.73-8.el6_8 base
mysql-embedded.i686 5.1.73-8.el6_8 base
mysql-embedded.x86_64 5.1.73-8.el6_8 base
mysql-embedded-devel.i686 5.1.73-8.el6_8 base
mysql-embedded-devel.x86_64 5.1.73-8.el6_8 base
mysql-libs.i686 5.1.73-8.el6_8 base
mysql-server.x86_64 5.1.73-8.el6_8 base
mysql-test.x86_64 5.1.73-8.el6_8 base
mysql55-mysql-debuginfo.x86_64 5.5.41-2.el6.centos.alt debug
pcp-pmda-mysql.x86_64 3.10.9-9.el6 base
qt-mysql.i686 1:4.6.2-28.el6_5 base
qt-mysql.x86_64 1:4.6.2-28.el6_5 base
rsyslog-mysql.x86_64 5.8.10-10.el6_6 base
rsyslog7-mysql.x86_64 7.4.10-7.el6 base
yum install mysql-server
[root@localhost ~]# rpm -qi mysql-server
Name : mysql-server Relocations: (not relocatable)
Version : 5.1.73 Vendor: CentOS
Release : 8.el6_8 Build Date: Thu 26 Jan 2017 02:25:43 PM PST
Install Date: Tue 16 Jan 2018 12:15:32 AM PST Build Host: c1bm.rdu2.centos.org
Group : Applications/Databases Source RPM: mysql-5.1.73-8.el6_8.src.rpm
Size : 25884131 License: GPLv2 with exceptions
Signature : RSA/SHA1, Thu 26 Jan 2017 02:35:28 PM PST, Key ID 0946fca2c105b9de
Packager : CentOS BuildSystem
URL : http://www.mysql.com
Summary : The MySQL server and related files
Description :
MySQL is a multi-user, multi-threaded SQL database server. MySQL is a
client/server implementation consisting of a server daemon (mysqld)
and many different client programs and libraries. This package contains
the MySQL server and some accompanying files and directories. 二、启动mysql-server服务
使用root权限，执行：
/etc/init.d/mysqld start
service mysqld start三、mysql登陆使用
开启mysql-server后，在普通账号下，登陆mysql成功：
[dup@localhost ~]$ mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.1.73 Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
[root@localhost ~]# mysql
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
然后通过如下命令登陆：
[root@localhost ~]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO) denied for user 'root'@'localhost' (using password: NO)
应该是安装后没有设置root密码，需要设置root密码
[root@localhost ~]#mysqladmin -u root -p password 123456 ###设置root密码为123456
Enter password:
mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'root'@'localhost' (using password: YES)'
但是依然有这个错误，网上查了下，使用如下方法解决了此问题：
[root@localhost ~]# /etc/init.d/mysqld stop
[root@localhost ~]# mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
[root@localhost ~]# mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('newpassword') where USER='root';
mysql> FLUSH PRIVILEGES;
mysql> quit
[root@localhost ~]# /etc/init.d/mysqld restart
[root@localhost ~]# mysql -u root -p
Enter password: <输入新设的密码newpassword>
mysql>