errors after installation

Help, how to bring it to work?

Warning: session_start() [function.session-start]: open(/tmp/sess_aa979faecc5030a237e9bc7d7e2a1831, O_RDWR) failed: No such file or directory (2) in /phpns/inc/header.php on line 22

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /phpns/inc/header.php:22) in /phpns/inc/header.php on line 22

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /phpns/inc/header.php:22) in /phpns/inc/header.php on line 22

Warning: Cannot modify header information - headers already sent by (output started at /phpns/inc/header.php:22) in /phpns/inc/auth.php on line 37

Warning: Unknown: open(/tmp/sess_aa979faecc5030a237e9bc7d7e2a1831, O_RDWR) failed: No such file or directory (2) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0