Make sure that your mysql user has permission to access the file system (the FILE privilege). GRANT ALL does not do this. You can check your user by doing:

select user, host, file_priv from mysql.user;

To enable:

grant FILE on *.* to 'root'@'localhost';flush privileges;

Also make sure that mysqld can write to the specified folder (./sql below). To dump:

mysqldump -uroot -p your_database --tab=./sql

Importing back is a two step process, DDL first followed by tab-delimited data:

DDL

cat sql/*.sql | mysql -uroot -p your_database

Tab delimited data

NOTE: The path you provide MUST be absolute. Nevermind, you can use --local to fix
NOTE: The -d parameter means DELETE from the current table before importing!

mysqlimport --local -uroot -p -d your_database sql/*.txt

Additionally, you might want to de-domain your files (for instance, if you’re backing up a WordPress site)

find sql/ -type f -name '*.txt' -exec sed -i 's/old_domain.com/place_holder/g' {} \;