此篇文章源于在Ubuntu 上启动Mysql的报错：ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'，以下记录在Ubuntu 16.04上重新安装Mysql的步骤。
卸载Mysql
# 移除与mysql相关的应用
sudo apt-get autoremove mysql* --purge
# 移除apparmor，它是在安装mysql-server时自动安装的依赖包
sudo apt-get remove apparmor
# 移除mysql的配置文件和相关目录
sudo rm /var/lib/mysql/ -R
sudo rm /etc/mysql/ -R
卸载期间如果遇到问题，可以一个卸载，再不行就重启电脑，然后重新卸载。
安装Mysql
sudo apt-get install mysql-server
这一步会安装以下包：
apparmor
mysql-client-5.7
mysql-common
mysql-server
mysql-server-5.7
mysql-server-core-5.7
因此无需再手动安装它们，在安装过程中在终端会提示输入root用户的密码，请注意保管，安装完成后就会启动Mysql。
当然安装，可能不会那么顺利，比如以下：
dpkg: error processing package mysql-community-server (--install):
dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of mysql-server:
mysql-server depends on mysql-community-server (= 5.7.17-1ubuntu16.10); however:
Package mysql-community-server is not configured yet.
dpkg: error processing package mysql-server (--install):
dependency problems - leaving unconfigured
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu16) ...
遇到这种问题多是依赖包的安装出现了问题，导致mysql无法启动，无法完成mysql的配置。当在网上搜索的结果无法解决问题时，请记住重启下电脑或者服务器，这是我第三次通过重启服务器解决了mysql的安装问题。
启动和关闭mysql服务器
- 启动
service mysql start
- 关闭
service mysql stop
- 重启
service mysql reload
- 查看mysql服务器状态
systemctl status mysql.service
- 查看mysql监听的端口
netstat -tap | grep mysql
ubuntu@iZ2zees2pdrgl9x5nmwp9dZ:~$ sudo netstat -tap | grep mysql
[sudo] password for ubuntu:
tcp 0 0 localhost:mysql *:* LISTEN 6761/mysqld
或者
netstat -atnp
ubuntu@iZ2zees2pdrgl9x5nmwp9dZ:~$ sudo netstat -atnp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 787/nginx -g daemon
tcp 0 0 127.0.0.1:5002 0.0.0.0:* LISTEN 12808/python
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 6761/mysqld
tcp 0 0 0.0.0.0:9999 0.0.0.0:* LISTEN 1871/server.js
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 787/nginx -g daemon
tcp 0 0 172.17.33.108:53 0.0.0.0:* LISTEN 740/named
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 900/sshd
tcp 0 0 127.0.0.1:953 0.0.0.0:* LISTEN 740/named
tcp 0 0 172.17.33.108:22 111.199.187.119:9569 ESTABLISHED 13054/sshd: ubuntu
tcp 0 296 172.17.33.108:22 111.199.187.119:10777 ESTABLISHED 13220/sshd: ubuntu
tcp 0 0 172.17.33.108:443 123.125.71.45:56773 TIME_WAIT -
tcp 0 0 127.0.0.1:42632 127.0.0.1:9999 TIME_WAIT -
tcp 0 0 172.17.33.108:80 92.119.113.26:33342 SYN_RECV -
tcp 0 0 172.17.33.108:80 92.119.113.26:41371 SYN_RECV -
tcp 0 0 172.17.33.108:443 92.119.113.26:60997 SYN_RECV -
tcp 0 0 172.17.33.108:33366 100.100.30.26:80 ESTABLISHED 838/AliYunDun
tcp 0 0 127.0.0.1:42634 127.0.0.1:9999 TIME_WAIT -
tcp 0 0 172.17.33.108:443 92.119.113.26:61717 SYN_RECV -
