Hide boot on-screen errors, or get TV-out working on ATI Radeon X300
tomh0665 at gmail.com
Mon Dec 8 11:04:47 UTC 2014
On Mon, Dec 8, 2014 at 2:45 AM, Marius Gedminas <marius at pov.lt> wrote:
> On Sun, Dec 07, 2014 at 02:33:47PM -0500, John Hupp wrote:
>> 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
>> 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
> 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‐
> (/proc/sys is one of the possible ways of changing systcl settings,
> which I guess explain why this is documented in proc(5).)
You can find the same explanation of the four _loglevels in
in a more readable format (to my eyes).
As mentioned in "man 5 proc", you'll find the explanation of the
priorities in "man 2 syslog"; you can also find it in
"/usr/include/x86_64-linux-gnu/.../syslog.h" (on x86_64/amd64).
"man 2 syslog" on 15.04 also includes the text of the kernel.org
document above (clarified/updated).
If you're not on 15.04, you can get the latest man-pages (manpages in
untar it, and run "man man-pages-3.75/man2/syslog.2"
"3 4 1 3" is a more standard setting than "3 3 3 3".
It's better to set 4 (WARNING, the vanilla default) rather than 3
(ERR) for messages that don't have a priority, since, if a message
really is an error, it'll (should?) be tagged as such.
By setting minimum_console_loglevel to 3, you're potentially making
printk more verbose on the console.
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