MySQL Got error 24 Too many open files

For ubuntu, see Ubuntu 18.04 MariaDB 10.2 Too many open files

On taking MySQL backup with mysqldump, i get following error

mysqldump: Got error: 1030: "Got error 24 "Too many open files" from storage engine MyISAM" when using LOCK TABLES
mysqldump: Error: 'Out of resources when opening file '/tmp/#sql_f68_2.MAD' (Errcode: 24 "Too many open files")' when trying to dump tablespaces

This is because open_files_limit limit in MySQL. To verify login to MySQL server and run

select @@open_files_limit;

This will give you current value of open_files_limit.

To increase, edit /etc/my.cnf file, add

vi /etc/my.cnf

Add under [mysqld] section

open_files_limit = 5000

Now restart MySQL server

systemctl restart mysql