Redmine2.2.0启动报mysql连接错误

在虚拟机CentOS 5装了个dotProject后，又装了个redmine2.2.0,启动时发现前几天正常运行的Redmine启动不了了，控制台输出错误信息如下：

=> Booting WEBrick
=> Rails 3.2.9 application starting in production on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/usr/local/lib/ruby/gems/1.8/gems/activerecord-3.2.9/lib/active_record/connection_adapters/mysql_adapter.rb:411:in `real_connect': Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2) (Mysql::Error)
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.2.9/lib/active_record/connection_adapters/mysql_adapter.rb:411:in `connect'

看错误信息是无法通过/tmp/mysql.sock连接mysql数据库，记得安dotProject时要安装php5,好像php5也是通过/tmp/mysql.sock连接的数据库，但是dotProject运行正常，通过查phpinfo()函数显示，MYSQL_SOCKET 指向的路径是/tmp/mysql.sock，用命令查看ls -l /tmp 没有发现mysql.sock文件，奇怪呀，没了mysql.sock文件php还能照样跑，ruby就不行了，报错：不能连接mysql。至于原因还要慢慢查找。

经过验证，解决redmine的这个错误，有两种方法可以采用

1. 建立软链接：用find / -name mysql.sock 命令找到mysql.sock的绝对路径，例如 /var/lib/mysql/mysql.sock。建立软链接：ln -s /var/lib/mysql/mysql.sock /tmp/mysql.sock.
   
2. 更改redmine的配置文件database.yml,添加socket参数 ：找到redmine所在的目录，进入config文件夹，编辑database.yml文件，加入socket = /var/lib/mysql/mysql.sock 例如

   # MySQL (default setup).
   
   production:
     adapter: mysql
     database: redmine
     host: localhost
     username: root
     password: root
     encoding: utf8
     socket: /var/lib/mysql/mysql.sock
   
   development:
     adapter: mysql
     database: redmine_development
     host: localhost
     username: root
     password: root
     encoding: utf8
     socket: /var/lib/mysql/mysql.sock
    

相关命令：

查找指定目录下的软链接，如查找/tmp目录下的软链接

find /tmp -type l -ls

find /tmp -type l -exec ls -l '{}' \;

 

注意：l 是字母的l ，不是竖线！