MySQL：mysqldump生成数据库备份

Question

I have had written the following snippet that generates the mysql database dump and saves it on the server :

public function save_db_backup()
{
    $DBUSER=$this->db->username;
    $DBPASSWD=$this->db->password;
    $DATABASE=$this->db->database;

    $filename = $DATABASE . "-" . date("Y-m-d_H-i-s") . ".sql.gz";

    $save_path = $_SERVER['DOCUMENT_ROOT'] . '/application/assets/db_backups/' . $filename;

    $cmd = "mysqldump -u $DBUSER --password=$DBPASSWD $DATABASE | gzip --best > " . $save_path;

    exec( $cmd );
}

It has been working fine on my other server . But after moving my site to this new server, it has suddenly stopped working ie database backup file is not being saved at the path specified. Also, I have checked exec is enabled on the server plus the directory is readable and also writeable :

 is_readable($_SERVER['DOCUMENT_ROOT'] . '/application/assets/db_backups/') // true
 is_writable($_SERVER['DOCUMENT_ROOT'] . '/application/assets/db_backups/') // true

I have checked and the database credentials are alright. I have tried with the path to mysqldump and that didn't work either:

$cmd = "/usr/bin/mysqldump -u $DBUSER --password=$DBPASSWD $DATABASE | gzip --best > " . $save_path;

What problem could there possibly be?

Answer 1

You should check what user launches the command, and then if the dir is readable and also writeable by THAT user. If you are launching it from a PHP script, it's the probable cause.