默認情況下，新安裝的 mariadb 的密碼為空，在shell終端直接輸入 mysql 就能登陸數據庫。

如果是剛安裝第一次使用，請使用 mysql_secure_installation 命令初始化。

# mysql_secure_installationNOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDBSERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!In order to log into MariaDB to secure it, we'll need the current
password for the root user.  If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.Enter current password for root (enter for none):
OK, successfully used password, moving on...Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorisation.Set root password? [Y/n] y
New password:
Re-enter new password:
Password updated successfully!
Reloading privilege tables..... Success!By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.Remove anonymous users? [Y/n] y... Success!Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.Disallow root login remotely? [Y/n] y... Success!By default, MariaDB comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.Remove test database and access to it? [Y/n] y- Dropping test database...... Success!- Removing privileges on test database...... Success!Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.Reload privilege tables now? [Y/n] y... Success!Cleaning up...All done!  If you've completed all of the above steps, your MariaDB
installation should now be secure.Thanks for using MariaDB!

---

這里針對的是知道 root 密碼，而需要修改的情況。

兩種修改方法：

1、直接在shell命令行使用 mysqladm 命令修改。

# mysqladmin -uroot -poldpassword password newpassword這種方法的弊端在于會明文顯示密碼。

2、登陸數據庫修改密碼。

# mysql -uroot -p2.1 更新 mysql 庫中 user 表的字段：
MariaDB [(none)]> use mysql;  
MariaDB [mysql]> UPDATE user SET password=password('newpassword') WHERE user='root';  
MariaDB [mysql]> flush privileges;  
MariaDB [mysql]> exit;2.2 或者，使用 set 指令設置root密碼：
MariaDB [(none)]> SET password for 'root'@'localhost'=password('newpassword');  
MariaDB [(none)]> exit; 

如果是忘記了 root 密碼，則需要以跳過授權的方式啟動 mariadb 來修改密碼。

1、先停掉服務。

# systemctl stop mariadb

2、使用跳過授權的方式啟動 mariadb。

# mysqld_safe --skip-grant-tables &
[1] 1441
[root@centos7 ~]# 170531 02:10:28 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'.
170531 02:10:28 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql# ps -ef | grep 1441
root      1441   966  0 02:10 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --skip-grant-tables
mysql     1584  1441  0 02:10 pts/0    00:00:00 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --skip-grant-tables --log-error=/var/log/mariadb/mariadb.log --pid-file=/var/run/mariadb/mariadb.pid --socket=/var/lib/mysql/mysql.sock

3、當跳過授權啟動時，可以不需要密碼直接登陸數據庫。登陸更新密碼即可。

# mysql
MariaDB [(none)]> use mysql;  
MariaDB [mysql]> UPDATE user SET password=password('newpassword') WHERE user='root';  
MariaDB [mysql]> flush privileges;   
MariaDB [mysql]> exit; 更新密碼后，在跳過授權啟動時也不能空密碼直接登陸了。

4、關閉跳過授權啟動的進程：

# kill -9 1441 

5、正常啟動 mariadb：

# systemctl start mariadb