ubuntu16.04卸载mysql5.7安装mysql5.6

1. 删除mysql
a. sudo apt-get autoremove --purge mysql-server-5.0
b. sudo apt-get remove mysql-server
c. sudo apt-get autoremove mysql-server
d. sudo apt-get remove mysql-common (非常重要)
2. 清理残留数据
dpkg -l |grep ^rc|awk '{print $2}' |sudo xargs dpkg -P

如果报如下错误，证明你的系统中没有残留配置文件了，无须担心。

dpkg: --purge needs at least one package name argument

Type dpkg --help for help about installing and deinstalling packages [*];
Use `dselect' or `aptitude' for user-friendly package management;
Type dpkg -Dhelp for a list of dpkg debug flag values;
Type dpkg --force-help for a list of forcing options;
Type dpkg-deb --help for help about manipulating *.deb files;
Type dpkg --license for copyright license and lack of warranty (GNU GPL) [*].

Options marked [*] produce a lot of output - pipe it through `less' or `more' !
下面安装mysql5.6
你必须先删除这些文件夹：/etc/mysql/ /var/lib/mysql /var/log/mysql/var/lib/mysql-filters /var/lib/mysql-keyring和这个文件：/var/lib/mysql/debian-5.7.flag - T0m3kk 7月22日在12:41
1. sudo apt-get install software-properties-common
2. $ sudo add-apt-repository -y ppa:ondrej/mysql-5.6
3. $ sudo apt-get update
4. $ sudo apt-get install mysql-server-5.6