Reduce boot time console messages?

[Valdis.Kletnieks at vt.edu]

On Sat, 03 Aug 2013 20:27:55 +0800, Woody Wu said:
> Hi,
>
> My kernel is printing too many messages at boot time from a special
> device driver (j2ffs filesystem). I belive these kernel messages are
> level DEBUG. If don't change the kernel code, is there anyway to print
> only some higher level of messages?

In your kernel source tree, there's a file called Documentation/kernel-parameters.txt
and in it, we find documentation  of the following two boot-time parameters:


        ignore_loglevel [KNL]
                        Ignore loglevel setting - this will print /all/
                        kernel messages to the console. Useful for debugging.
                        We also add it as printk module parameter, so users
                        could change it dynamically, usually by
                        /sys/module/printk/parameters/ignore_loglevel.
...

        loglevel=       All Kernel Messages with a loglevel smaller than the
                        console loglevel will be printed to the console. It can
                        also be changed with klogd or other programs. The
                        loglevels are defined as follows:

                        0 (KERN_EMERG)          system is unusable
                        1 (KERN_ALERT)          action must be taken immediately
                        2 (KERN_CRIT)           critical conditions
                        3 (KERN_ERR)            error conditions
                        4 (KERN_WARNING)        warning conditions
                        5 (KERN_NOTICE)         normal but significant condition
                        6 (KERN_INFO)           informational
                        7 (KERN_DEBUG)          debug-level messages

In addition, there may or may not be a module parameter to control the
logging level of the particular module - look for the word 'debug' in that
file.  There's also the 'dynamic debugging' facility which the module may
be coded to support....
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