之前介绍了如何卸载Mysql，下面介绍下Mariadb

Uninstall mariadb-server

To remove just mariadb-server package itself from Debian 9 (Stretch) execute on terminal:

sudo apt-get remove mariadb-server

Uninstall mariadb-server and it's dependent packages
To remove the mariadb-server package and any other dependant package which are no longer needed from Debian Stretch.

sudo apt-get remove --auto-remove mariadb-server

Purging mariadb-server
If you also want to delete configuration and/or data files of mariadb-server from Debian Stretch then this will work:

sudo apt-get purge mariadb-server

To delete configuration and/or data files of mariadb-server and it's dependencies from Debian Stretch then execute:

sudo apt-get purge --auto-remove mariadb-serve
apt-get remove mariadb-client-10.1 mariadb-client-core-10.1 mariadb-common mariadb-server-10.1 mariadb-server-core-10.1

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Centos常规操作：

1、卸载mariadb：yum remove mariadb

2、删除配置文件：rm -f /etc/my.cnf

3、删除数据目录：rm -rf /var/lib/mysql/

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卸载清理工作全部完成，可以重新安装了。