server stop working :(

i got error during open phpmyadmin anybody help me pls
Error during session start; please check your PHP and/or webserver log file and configure your PHP installation properly. Also ensure that cookies are enabled in your browser.

session_start(): open(SESSION_FILE, O_RDWR) failed: No space left on device (28)

session_start(): Failed to read session data: files (path: /var/lib/php/session)