In Codeigniter its related to session folder apsolutae path need to edit according to operating system.Also must have permission of that folder to create file.

For ubuntu users set  sess_save_path in  Codeigniter:In ubuntu for storing session files inside default tmp folder.

 

$config['sess_save_path'] = '\tmp'; 

For windows (Local Setup ) users set  sess_save_path in  Codeigniter : Open your codeigniter config.php find sess_save_path variable add this value 

 $config['sess_save_path'] =APPPATH.'tmp/'; 

 Now your session stored in codeigniter application folder inside tmp folder.

 

For windows (Live Server Setup ) users set  sess_save_path in  Codeigniter : Find the temp directory on your windows server and give  apsolutae path

 $config['sess_save_path'] ='G:/abcs/temp'; 

 Now your session stored in server temp folder.