mkdir() No such file or directory Session_files_driver.php

Have you set the $config['sess_save_path'] to a folder that your app has write permissions for?
http://www.codeigniter.com/user_guide/li...les-driver

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = NULL;
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

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