The four values in printk denote:

  • console_loglevel - messages with a priority higher than this will be printed to the console
  • default_message_loglevel - messages without an explicit priority will be printed with this priority
  • minimum_console_loglevel - minimum (highest) value to which console_loglevel can be set
  • default_console_loglevel - default value for console_loglevel

These values influence printk() behavior when printing or logging error messages. See syslog(2) for more info on the different loglevels.