sudo apt-get autoremove --purge MysqL-server-5.0
sudo apt-get remove MysqL-server
sudo apt-get autoremove MysqL-server
sudo apt-get remove MysqL-common //这个很重要
上面的其实有一些是多余的。
下载对应的Linux安装包，注意32位与64位的区别，然后放到/home/ubuntu
解压 tar -xzf *tar.gz
我不新建用户，直接用系统默认的ubuntu安装
解压后，/home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686
改变目录的所有者
sudo chown -R ubuntu:ubuntu /home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686
安装共享库libaio1
sudo apt-get install libaio1
进入目录/home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686试图安装：./scripts/MysqL_install_db --user=ubuntu
会发现根本不行，
To start MysqLd at boot time you have to copy
support-files/MysqL.server to the right place for your system
于是，
cd /etc/init.d
sudo ln -s /home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686/support-files/MysqL.server
sudo /etc/init.d/MysqL.server start
/etc/init.d/MysqL.server: my_print_defaults: not found
sudo cp /home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686/bin/my_print_defaults /usr/bin
还是不行，找到my.cnf
MysqLd --verbose --help|grep my.cnf
2016-05-31 16:36:09 0 [Note] MysqLd (MysqLd 5.6.30-log) starting as process 3379 ...
2016-05-31 16:36:09 3379 [Note] Plugin 'FEDERATED' is disabled.
/etc/my.cnf /etc/MysqL/my.cnf /usr/local/MysqL/etc/my.cnf ~/.my.cnf
my.cnf,$MysqL_TCP_PORT,/etc/services,built-in default
可以看到MysqLd会去读取以上路径，于是复制
sudo cp /home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686/support-files/my-small.cnf /usr/local/MysqL/my.cnf
sudo cp -r /home/ubuntu/MysqL-5.5.56-linux-glibc2.5-i686/* /etc/MysqL/
sudo chmod -R 777 /usr/local/MysqL
sudo chown -r ubuntu:ubuntu /usr/local/MysqL
sudo /etc/init.d/MysqL.server start
Warning: World-writable config file '/usr/local/MysqL/my.cnf' is ignored
Failed to issue method call: Unit MysqL.service Failed to load: No such file or directory. See system logs and 'systemctl status MysqL.service' for details.
systemctlenableMysqL.server
Warning: World-writable config file '/etc/my.cnf' is ignored
查看my.cnf的权限
ls -l /etc/my.cnf
修复MysqL问题
chmod 644 /etc/my.cnf
sudo service MysqL.server stop
ln -s /usr/local/MysqL/data/MysqL.sock /var/run/MysqLd/MysqLd.sock
