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)
mysql>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
[Service]
LimitNOFILE=5000
#
systemctl daemon-reload
service mysqld restart
Once this was applied the Backups worked fine. You may raise the limits as required.