在Ubuntu中，默认情况下，只有最新版本的MySQL包含在APT软件包存储库中,要安装它，只需更新服务器上的包索引并安装默认包apt-get。
sudo apt-get update
sudo apt install mysql-server-5.7
需要先安装net-tools
sudo apt install net-tools
sudo netstat -tap | grep mysql
mysql -V
sudo cat /etc/mysql/debian.cnf
sudo mysql_secure_installation
配置项较多，如下所示：
#1
VALIDATE PASSWORD PLUGIN can be used to test passwords...
Press y|Y for Yes, any other key for No: N (我的选项)
#2
Please set the password for root here...
New password: (输入密码)
Re-enter new password: (重复输入)
#3
By default, a MySQL installation has an anonymous user,
allowing anyone to log into MySQL without having to have
a user account created for them...
Remove anonymous users? (Press y|Y for Yes, any other key for No) : N (我的选项)
#4
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? (Press y|Y for Yes, any other key for No) : N (我的选项)
#5
By default, MySQL comes with a database named 'test' that
anyone can access...
Remove test database and access to it? (Press y|Y for Yes, any other key for No) : N (我的选项)
#6
Reloading the privilege tables will ensure that all changes
made so far will take effect immediately.
Reload privilege tables now? (Press y|Y for Yes, any other key for No) : Y (我的选项)
systemctl status mysql.service
显示如下结果说明mysql服务是正常的：
连接到Mysql：
sudo mysql -uroot -p
mysql> select user, plugin from mysql.user;
mysql> update mysql.user set authentication_string=PASSWORD('123456'), plugin='mysql_native_password' where user='root';
mysql>flush privileges;
mysql> exit
sudo vi /etc/mysql/mysql.conf.d/mysqld.cnf
mysql -uroot -p
mysql>grant all ON *.* to root@'%' identified by '123456' with grant option;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
其中root@%，localhost就是本地访问，配置成%就是所有主机都可连接；第二个’123456’为你给新增权限用户设置的密码。
sudo /etc/init.d/mysql restart
想安装MySQL 8.0或者重装MySQL 5.7的前提条件，可以先删除已有的。
sudo apt autoremove --purge mysql-server-*
sudo apt remove mysql-server
sudo apt autoremove mysql-server
sudo apt remove mysql-common
dpkg -l |grep ^rc|awk '{print $2}' |sudo xargs dpkg -P