some questions about log level

some questions about log level

[loody]

hi all:
my questions are below:
1. Can I temporarily let kernel message show in stdout?
    I google some key word as "console_loglevel" and I found following methods:
     a. echo 8 > /proc/sys/kernel/printk
     b. write a simple program which calling "klogctl(8, NULL, level)"
Then I purposely connect/disconnect USB, but my console keep quiet.
But dmesg shows connect/disconnect messages.

2. what is differences between above a and b methods?
    Are they not to used to change console_loglevel?

3. is it possible the max level of "console_loglevel" doesn't mean it
will show on stdout?




-- 
Thanks for your help

some questions about log level

[Mulyadi Santosa]

On Mon, Dec 12, 2011 at 21:18, loody <miloody@gmail.com> wrote:
> hi all:
> my questions are below:
> 1. Can I temporarily let kernel message show in stdout?
> ? ?I google some key word as "console_loglevel" and I found following methods:
> ? ? a. echo 8 > /proc/sys/kernel/printk
> ? ? b. write a simple program which calling "klogctl(8, NULL, level)"
> Then I purposely connect/disconnect USB, but my console keep quiet.
> But dmesg shows connect/disconnect messages.

Perhaps this document could explain the basics better than me:
http://lxr.linux.no/#linux+v3.1.5/Documentation/sysctl/kernel.txt#L405

Hope that helps...


-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

some questions about log level

[Jonathan Neuschäfer]

On Mon, Dec 12, 2011 at 10:18:20PM +0800, loody wrote:
> Then I purposely connect/disconnect USB, but my console keep quiet.

Which "console" are you looking at? It only works with the consoles
provided by the kernel (ttyN) on usual desktop distros, and not with
xterm-alikes.

HTH,
	Jonathan Neusch?fer

some questions about log level

[loody]

hi:

2011/12/13 Jonathan Neusch?fer <j.neuschaefer@gmx.net>:
> On Mon, Dec 12, 2011 at 10:18:20PM +0800, loody wrote:
>> Then I purposely connect/disconnect USB, but my console keep quiet.
>
> Which "console" are you looking at? It only works with the consoles
> provided by the kernel (ttyN) on usual desktop distros, and not with
> xterm-alikes.
I use ubuntu 11.04 and I use gnome terminal.
so you mean what I saw in gonme terminal may not be the ttyN that
enabled by kernel?
if that is the root cause, is it possible for me to switch my gonme
terminal to ttyN you mentioned?

Appreciate your help,

some questions about log level

[Mulyadi Santosa]

On Tue, Dec 13, 2011 at 08:57, loody <miloody@gmail.com> wrote:
> hi:
>
> 2011/12/13 Jonathan Neusch?fer <j.neuschaefer@gmx.net>:
>> On Mon, Dec 12, 2011 at 10:18:20PM +0800, loody wrote:
>>> Then I purposely connect/disconnect USB, but my console keep quiet.
>>
>> Which "console" are you looking at? It only works with the consoles
>> provided by the kernel (ttyN) on usual desktop distros, and not with
>> xterm-alikes.
> I use ubuntu 11.04 and I use gnome terminal.
> so you mean what I saw in gonme terminal may not be the ttyN that
> enabled by kernel?
> if that is the root cause, is it possible for me to switch my gonme
> terminal to ttyN you mentioned?
>
> Appreciate your help,

Jonathan refer to consoles you usually get when pressing Ctrl-Alt-F1
throught Ctrl-Alt-F6.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

some questions about log level

[loody]

hi all:
I can see the message, right now.
2011/12/13 Mulyadi Santosa <mulyadi.santosa@gmail.com>:
> On Tue, Dec 13, 2011 at 08:57, loody <miloody@gmail.com> wrote:
>> hi:
>>
>> 2011/12/13 Jonathan Neusch?fer <j.neuschaefer@gmx.net>:
>>> On Mon, Dec 12, 2011 at 10:18:20PM +0800, loody wrote:
>>>> Then I purposely connect/disconnect USB, but my console keep quiet.
>>>
>>> Which "console" are you looking at? It only works with the consoles
>>> provided by the kernel (ttyN) on usual desktop distros, and not with
>>> xterm-alikes.
>> I use ubuntu 11.04 and I use gnome terminal.
>> so you mean what I saw in gonme terminal may not be the ttyN that
>> enabled by kernel?
>> if that is the root cause, is it possible for me to switch my gonme
>> terminal to ttyN you mentioned?
>>
>> Appreciate your help,
>
> Jonathan refer to consoles you usually get when pressing Ctrl-Alt-F1
> throught Ctrl-Alt-F6.
>
BTW, is there any api I can flush all the messages in kernel buffer
ring before when I jump to BUG(), kernel checking MACRO?
my problem is:
1. I put more detail messages in the level 8, usually it will shows up
if I change console_loglevel or type dmesg.
2. I don't want it to show in normal operation.
3. but I want to see them before my driver jump to BUG() check point.
Thanks for your help,

some questions about log level

[loody]

hi all:
>
> Jonathan refer to consoles you usually get when pressing Ctrl-Alt-F1
> throught Ctrl-Alt-F6.
is it possible to direct kernel log to xterm-alikes console?
Thanks for your help in advance,

some questions about log level

[Mulyadi Santosa]

Hi...

On Fri, Jun 29, 2012 at 10:05 AM, loody <miloody@gmail.com> wrote:
> is it possible to direct kernel log to xterm-alikes console?
> Thanks for your help in advance,

it depends on your syslog daemon setting. Assuming you're using plain
old syslogd, perhaps you need to adjust /etc/syslog.conf to contain:
kern.*                                                 /dev/console

IIRC, desktop environment such KDE (I only check it on KDE 3.5.x) will
catch such message which is thrown to console and display it in a pop
up.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com