Same issue for me and my site is down with "Error establishing database connection"
Internal Server Error
500
failed to open session lockfile: FILE=/var/cpanel/sessions/raw/mizaanre:jxkWnDQimXmKx3i_9VlFGUhVJBKiRJ6lwiRv90vbLUSHI4hZ2n5ZgHCGA8j4MwDu.lock, No space left on device at...