前一段时间，可以从本地连接公司内部服务器的数据库，有一次停电之后，就再也连不上了，服务器磁盘也受到了损坏，很多表看着存在，却打不开，也无法drop。

后来通过phpmyadmin重命名表格，再重新导入修复好了，但是本地却连不上了。

一直想在本地连接linux服务器上的数据库，可老是超时连接不上，但是ping 服务器也能ping通，后来感觉可能是服务器数据库的对外端口可能禁了。

（1）首先要确认的是3306端口是不是对外开放了。mysql默认状态下是不开发对外访问的功能的，所以大多数这就是问题的所在。

     进入服务器，

root@ubuntu:/$ netstat -an | grep 3306 
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN   

     仔细查看，如果都是127.0.0.1，那么说明3306端口没有对外开放，只是监听本地的连接。

Solution：进入到mysql的配置文件所在目录（/etc/mysql/my.cnf）找到文件中如下内容：
# Instead of skip-networking the default is now to listen only on  
# localhost which is more compatible and is not less secure.  
bind-address  = 127.0.0.1  
将bind-address注释掉，或者改成客户端主机IP，重启之后，再查看端口

root@ubuntu:/$ netstat -an | grep 3306 
tcp6       0      0 :::3306                 :::*                    LISTEN     
tcp6       0      0 192.168.99.246:3306     192.168.99.45:11846     ESTABLISHED
tcp6       0      0 192.168.99.246:3306     192.168.99.45:11844     ESTABLISHED

已经打开，允许所有客户端连接，下面两条是我本地连接上的记录

（2）下面你还要确认的一件事就是确认客户端用户是否具有权限

mysql>grant all privileges on *.* to username@"%" identified by "password";

注意%后面要空一隔

上面的命令授予的用户权限可以访问mysql中的任意数据库(database)和表(table)。

附上配置

#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html

# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port        = 3306
socket        = /var/run/mysqld/mysqld.sock

# Here is entries for some specific programs
# The following values assume you have at least 32M ram

# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket        = /var/run/mysqld/mysqld.sock
nice        = 0

[mysqld]
#
# * Basic Settings
#
user        = mysql
pid-file    = /var/run/mysqld/mysqld.pid
socket        = /var/run/mysqld/mysqld.sock
port        = 3306
basedir        = /usr
datadir        = /var/lib/mysql
tmpdir        = /tmp
lc-messages-dir    = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address        = 127.0.0.1
#
# * Fine Tuning
#
key_buffer        = 160M
max_allowed_packet    = 10240M
thread_stack        = 192K
thread_cache_size       = 80
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover         = BACKUP
#myisam-recover-options = BACKUP,FORCE
#max_connections        = 100
#table_cache            = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit    = 10M
query_cache_size        = 160M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#log_slow_queries    = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
#       other settings you may need to change.
#server-id        = 1
#log_bin            = /var/log/mysql/mysql-bin.log
expire_logs_days    = 10
max_binlog_size         = 100M
#binlog_do_db        = include_database_name
#binlog_ignore_db    = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem

[mysqldump]
quick
quote-names
max_allowed_packet    = 10240M

[mysql]
#no-auto-rehash    # faster start of mysql but no tab completition

[isamchk]
key_buffer        = 16M

#
# * IMPORTANT: Additional settings that can override those from this file!
#   The files must end with '.cnf', otherwise they'll be ignored.
#