How to Fix an (errno: 24) in MySQL

When creating a large number of partitions or tables, MySQL may mysteriously stop working and you find this type of error on (HOSTNAME).err:

[ERROR] /usr/sbin/mysqld: Can’t open file: ‘./database/table.frm’ (errno: 24)

errno: 24 simply means that too many files are open for the given process. There is a read-only mysql variable called open_files_limit that will show how many open files are allowed by the mysqld:

SHOW VARIABLES LIKE 'open%'

The default 1024 is very low.

Edit your config file and change as following (/etc/my.cnf.d/server.cnf)

[mysqld]
open_files_limit = 100000