Hide boot on-screen errors, or get TV-out working on ATI Radeon X300

[Marius Gedminas]

On Sun, Dec 07, 2014 at 02:33:47PM -0500, John Hupp wrote:
> Victory!
> 
> I created /etc/sysctl.d/20-quiet-printk.conf with content:
> kernel.printk = 3 3 3 3
...
> Though I was curious to know a bit more about the mechanisms in
> play, I didn't dig much further than that.  I wondered, for
> instance, what behavior the default '4 4 1 7' specified, but never
> did find out.  The files in sysctl.d are installed by procps (see
> the List of Files link at
> http://packages.ubuntu.com/trusty/admin/procps). And these, in turn,
> are part of the kernel configuration governed by sysctl (see
> http://manpages.ubuntu.com/manpages/trusty/en/man8/sysctl.8.html).
> 
> Still looking for the meaning of '4 4 1 7' vs '3 3 3 3' I came to
> https://www.kernel.org/doc/Documentation/printk-formats.txt, but my
> eyes glazed over just skimming that, and I stopped there.

This is a bit unobvious, but you can find the description of the
kernel.printk sysctl setting in 
http://manpages.ubuntu.com/manpages/trusty/en/man5/proc.5.html:

    /proc/sys/kernel/printk
        The four values in this file are console_loglevel,  default_mes‐
        sage_loglevel,     minimum_console_level,    and    default_con‐
        sole_loglevel.  These values influence  printk()  behavior  when
        printing or logging error messages.  See syslog(2) for more info
        on the different loglevels.  Messages  with  a  higher  priority
        than  console_loglevel will be printed to the console.  Messages
        without an explicit  priority  will  be  printed  with  priority
        default_message_level.   minimum_console_loglevel is the minimum
        (highest)  value  to  which   console_loglevel   can   be   set.
        default_console_loglevel   is   the   default   value  for  con‐
        sole_loglevel.

(/proc/sys is one of the possible ways of changing systcl settings,
which I guess explain why this is documented in proc(5).)

Marius Gedminas
-- 
question = 0xFF;        // optimized Hamlet
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