Linux中Mariadb卸载
1、卸载mariadb：
yum remove mariadb
2、删除配置文件：
rm -f /etc/my.cnf1
3、删除数据目录：
rm -rf /var/lib/mysql/
Linux中修改mariadb数据库root密码
情况一：初始化数据库
当第一安装好数据库时，默认没有密码，可以通过以下命令进行修改，确认密码以后，一路Y即可完成任务。
mysql_secure_installation
# mysql_secure_installation
NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
SERVERS 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): # 直接回车就可以
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 #输入Y表示要设置密码
New password: # 新密码
Re-enter new password: # 确认密码
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 # 移除匿名用户
... 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 # 拒绝root远程登录，n, 不管y/n,都会拒绝root远程登录
... 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 # 删除test数掘库，y:删除 n: 不删除，
- 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 # 重新加载权限表，y.或者里启服务也可
... 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!
情况二：已知密码
两种修改方法：
1、直接在shell命令行使用 mysqladm 命令修改。
# mysqladmin -uroot -poldpassword password newpassword
这种方法的弊端在于会明文显示密码。
2、登陆数据库修改密码。
# mysql -uroot -p
2.1 更新 mysql 库中 user 表的字段：
MariaDB [(none)]> use mysql;
MariaDB [mysql]> UPDATE user SET password=password('newpassword') WHERE user='root';
或者
MariaDB [mysql]> ALTER USER 'root'@'localhost' IDENTIFIED BY 'newpassword';
MariaDB [mysql]> flush privileges;
MariaDB [mysql]> exit;
2.2 或者，使用 set 指令设置root密码：
MariaDB [(none)]> SET password for 'root'@'localhost' = password('newpassword');
MariaDB [(none)]> exit;
情况三：忘记现有密码
1、先停掉服务。
# systemctl stop mariadb
2、使用跳过授权的方式启动 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、当跳过授权启动时，可以不需要密码直接登陆数据库。登陆更新密码即可。
# mysql
MariaDB [(none)]> use mysql;
MariaDB [mysql]> UPDATE user SET password=password('newpassword') WHERE user='root';
MariaDB [mysql]> flush privileges;
MariaDB [mysql]> exit;
4、关闭跳过授权启动的进程：
# kill -9 1441
5、正常启动 mariadb：
# systemctl start mariadb
至此完成数据库密码修改！