ubuntu14.0默认安装mysql是5.5,很多时候需要安装5.7，于是我们可以将mysql升级。
1、下载mysql-apt的配置包，并安装
wget https://dev.mysql.com/get/mysql-apt-config_0.8.1-1_all.deb
sudo dpkg -i mysql-apt-config_0.8.1-1_all.deb
在安装的过程中，会要求选择mysql版本，选择mysql5.7版本后，点击“OK”。
2、更新apt-get索引
sudo apt-get update
更新过程中出现如下错误：
W: Failed to fetch.......
在/etc/resolv.conf,加上dns
nameserver 202.96.174.133
nameserver 202.96.128.68
nameserver 8.8.8.8
再次更新，如果还有错误，报如下错误
W: GPG error: http://repo.mysql.com jessie InRelease: The following signatures were invalid: KEYEXPIRED 1487236823 KEYEXPIRED 1487236823 KEYEXPIRED 1487236823
解决办法如下：
先查看执行命令：apt-key list
---------------------------------------------
pub 4096R/89DF5277 2010-07-11
uid Guillaume Plessis <gui@dotdeb.org>
sub 4096R/3D624A3B 2010-07-11
sub 4096R/A2098A6E 2010-07-11
pub 1024D/5072E1F5 2003-02-03 [expired: 2017-02-16]
uid MySQL Release Engineering <mysql-build@oss.oracle.com>
---------------------------------------------
删除mysql 的repository GPG key，删除命令如下：
sudo apt-key del 5072E1F5
---------------------------------------------
删除完了之后，检查还有没有那个mysql的key
没有了，执行命令：apt-key adv --keyserver pgp.mit.edu --recv-keys A4A9406876FCBD3C456770C88C718D3B5072E1F5
如下输出
--------------------------------------------------
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --homedir /tmp/tmp.z5SEIWWrbt --no-auto-check-trustdb --trust-model always --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-jessie-automatic.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-jessie-security-automatic.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-jessie-stable.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-squeeze-automatic.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-squeeze-stable.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-wheezy-automatic.gpg --keyring /etc/apt/trusted.gpg.d/debian-archive-wheezy-stable.gpg --keyring /etc/apt/trusted.gpg.d/php.gpg --keyserver pgp.mit.edu --recv-keys A4A9406876FCBD3C456770C88C718D3B5072E1F5
gpg: requesting key 5072E1F5 from hkp server pgp.mit.edu
gpg: key 5072E1F5: "MySQL Release Engineering <mysql-build@oss.oracle.com>" 62 new signatures
gpg: Total number processed: 1
gpg: new signatures: 62
--------------------------------------------------
完成后，再执行apt-get update
3、安装数据库，在安装过程中，会自动卸载已经安装的老版本数据。
sudo apt-get install mysql-server
4、安装mysql 后，使用mysql_upgrade升级数据库文件版本
sudo mysql_upgrade -uroot -p'youpassword'
5、重启mysql,并检查数据是否正常
sudo service mysql restart
mysqlcheck -uroot -p'youpassword' --all-databases
6、检查mysql版本，升级成功
创建新用户
通过root用户登录之后创建
>> grant all privileges on *.* to testuser@localhost identified by "123456" ; // 创建新用户，用户名为testuser，密码为123456 ；
>> grant all privileges on *.* to testuser@localhost identified by "123456" ; // 设置用户testuser，可以在本地访问mysql
>> grant all privileges on *.* to testuser@"%" identified by "123456" ; // 设置用户testuser，可以在远程访问mysql
>> flush privileges ; // mysql 新设置用户或更改密码后需用flush privileges刷新MySQL的系统权限相关表，否则会出现拒绝访问，还有一种方法，就是重新启动mysql服务器，来使新设置生效
最后：service mysql restart
3306权限不能访问的话：iptables -A INPUT -p tcp --dport 3306 -j ACCEPT
最后建议还是卸载后重装
卸载：
sudo apt-get autoremove mysql* --purge
sudo apt-get remove apparmor
sudo rm /var/lib/mysql/ -R
sudo rm /etc/mysql/ -R
检查是否卸载干净
dpkg -l | grep mysql # 若没有返回，说明已完成卸载
安装,要安装5.7的还是先执行步骤1,2：
1. sudo apt-get install mysql-server
2. sudo apt-get install mysql-client
3. sudo apt-get install libmysqlclient-dev
安装过程中会提示设置密码什么的，注意设置了不要忘了，安装完成之后可以使用如下命令来检查是否安装成功：
sudo netstat -tap | grep mysql
安装完毕！！！
- MySql Host is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts' 解决方法
mysqladmin -uroot -ppasswd flush-hosts
