Plesk Onyx 17.8 :: Backup Error :: Errcode: 24 – Too many open files

A recently setup Plesk on CentOS 7 Server was showing errors under Backup manager :

Unable to execute SQL: Out of resources when opening file '/tmp/#sql_5226_0.MYI' (Errcode: 24 - Too many open files). SQL query: SHOW FULL COLUMNS IN `catalogindex_minimal_price`

The MySQL configured was default and showed limits as below :

mysql> show global variables like 'open%';
| Variable_name    | Value |
| open_files_limit | 1000  |
1 row in set (0.00 sec)


To raise the limits I had to create a directory and create a configuration file as below :

cd  /usr/lib/systemd/system
mkdir mysql.service.d
cd mysql.service.d/
nano -w override.conf

# cat override.conf
systemctl daemon-reload
service mysqld restart

Once this was applied the Backups worked fine. You may raise the limits as required.