The error message is:
Code:
mysql> show databases;
ERROR 1018 (HY000): Can't read dir of '.' (errno: 24)
And MySQL's error records show as:

Code:
Mar 18 04:15:28 admon mysqld: 104719  4:15:28 [ERROR] Error in accept: Too many open files
[Resolved]
A possible solution is:
This error is due to max open-file limitation in mysql. You need to pay attention to two configs:
1, the system wide max open file limitation. On Debian / Redhat / CentOS system, it can be set in /etc/security/limits.conf

2, The limitations from MySQL itself. It's controlled by one parameter open_files_limit.

Code:
mysql> show variables like 'open_files_limit';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| open_files_limit | 65536 |
+------------------+-------+
1 row in set (0.00 sec)