Reduce boot time console messages?

Woody Wu narkewoody at
Sun Aug 4 23:07:26 EDT 2013

On Sat, Aug 03, 2013 at 10:08:42AM -0400, Valdis.Kletnieks at wrote:
> 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

Valdis, thank you very much.  I just passed loglevel=7 as kernel command
line and hope it can suspress KERN_DEBUG messages printed out to console
at boot time. But, it seems not work. A lot of debug level messages from
jffs2 module still print out. I will go to check where is wrong.

> 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....

I can't go back to yesterday - because I was a different person then

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