Mysql奇怪的连接问题

Question

我有一个奇怪的问题。我的MySQL 5.1安装在我的Ubuntu 9.04上。

我用了很长时间（比如3个月），一切都正常。直到我面对这个奇怪的问题。

当我要连接到一个随机数据库中，我得到这个消息：

ERROR 2006 (HY000): MySQL server has gone away 
No connection. Trying to reconnect... 
Connection id: 1 
Current database: test_cake 

ERROR 2006 (HY000): MySQL server has gone away 
No connection. Trying to reconnect... 
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111) 
ERROR: 
Can't connect to the server 

它只能与某些数据库发生，而有些则完全有用的和健康的。之后，如果我尝试重新启动服务器，我得到了这个。

shell> /etc/init.d/mysql restart 
* Stopping MySQL database server mysqld          cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
                     [fail] 
* Starting MySQL database server mysqld          cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
cat: /var/run/mysqld/mysqld.pid: Permiso denegado 
                     [fail] 
("permiso denegado" is "permission denied"). 

我不知道该怎么做。我更改了/var/run/mysqld/mysqld.pid属性，但仍然无法正常工作。

任何人都可以帮助我吗？

Answer 1

看看这将工作：

su     (become root) 
su mysql    (become user mysql, or whatever account mysql runs as) 
cd /var/run/mysqld (see if the directory is accessible to mysql) 
cat mysqld.pid  (see if the file is accessible)