hi !
i was wondering how to make kernel messages appear on /dev/ttyS0 without a reboot, i.e. kernelparam "console=ttyS0"
after playing for a while with setconsole, setterm and klogconsole i didn`t find a way to make that happen.
i can do "setconsole /dev/tty1 </dev/console" and then "echo test >/dev/console" and see "test" on tty1
"setterm -msg on -msglevel 8 >/dev/console" (or >/dev/tty1), modprobe loop;rmmod loop - and i see the kernel message there
i can do "setconsole /dev/ttyS0 </dev/console" and then "echo test >/dev/console" and see "test" on ttyS0
BUT :
"setterm -msg on -msglevel 8 >/dev/console" (or >/dev/ttyS0), modprobe loop;rmmod loop ...... nothing!
since i came across jan`s posting from 2005, which didn`t get a reply i think it`s not that stupid to ask again...
any clue how to do that at runtime or what`s the issue here ? (see excerpts below)
i can set
regards
roland
List: linux-kernel
Subject: Redirect kernel console
From: Jan Engelhardt <jengelh () linux01 ! gwdg ! de>
Date: 2005-08-13 12:48:22
Message-ID: Pine.LNX.4.61.0508131447220.4457 () yvahk01 ! tjqt ! qr
[Download message RAW]
Hi,
there is a klogconsole utiltity that allows to change the console to which
kernel messages are printed. However, is it possible to redirect to ttyS0
without a reboot?
Jan Engelhardt
-------
>> Subject: Re: serial console _after_ boot ?
>> > Setterm outputs the correct escape sequences to stdout. You can
>> > configure another tty using 'setterm -msglevel 8 -msg on > /dev/ttyS0'.
>> > I tested this on the standard kernel consoles (/dev/tty1-9), and it
>> > worked. You obviously need root access to write the escape sequences to
>> > the tty's.
>>
>> oh - yes, this works! but with tty1-9 only.
>> not with ttyS0 :(
>
>.....as the docs tell.....
>
> Some options however (marked "virtual consoles only" below) do not correspond to a terminfo(5) capability.
>
> -msg [on|off] (virtual consoles only)
> Enables or disables the sending of kernel printk() messages to the console.
>
> -msglevel 1-8 (virtual consoles only)
> Sets the console logging level for kernel printk() messages. All messages strictly more important than this
> will be printed, so a logging level of 0 has the same effect as -msg on and a logging level of 8 will print
> all kernel messages. klogd(8) may be a more convenient interface to the logging of kernel messages.
> > > but i don`t have change_console.
> > > searched the net and found that this eventually should be part of sysvinit package.
> > > but mine doesn`t provide that tool.
> > >
> > > found "setconsole" which looks like something similar, but "setconsole /dev/ttyS0 < /dev/console"
> > > doesn`t have any effect
> >
> > What distribution do you use? I have change_console on gentoo, yet I
> > cannot find the tool on a debian etch. But that's a vserver, so it's
> > probably not a reference.
>
> i have opensuse 10.3
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On Jan 3 2008 13:43, [email protected] wrote:
>
>hi !
>
>i was wondering how to make kernel messages appear on /dev/ttyS0 without a reboot, i.e. kernelparam "console=ttyS0"
The solution is simple... the following piece of code is inside
opensuse-10.3/src/sysvinit-2.86-115.src.rpm#showconsole-1.08.tar.bz2#showconsole-1.08/blogd.c
(void)ioctl(0, TIOCCONS, NULL); /* Undo any current map if any */
if (ioctl(pts, TIOCCONS, NULL) < 0)
error("can not set console device to %s: %s\n", ptsname, strerror(errno));
so I suppose that's it. Write up a new program that calls the ioctl
on a tty, and you should be done. IOW:
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
int main(void)
{
int fd = open("/dev/ttyS0", O_RDWR);
ioctl(0, TIOCCONS, NULL);
ioctl(fd, TIOCCONS, NULL);
}
In article <[email protected]>,
Jan Engelhardt <[email protected]> wrote:
>
>On Jan 3 2008 13:43, [email protected] wrote:
>>
>>hi !
>>
>>i was wondering how to make kernel messages appear on /dev/ttyS0
>without a reboot, i.e. kernelparam "console=ttyS0"
>
>The solution is simple... the following piece of code is inside
>opensuse-10.3/src/sysvinit-2.86-115.src.rpm#showconsole-1.08.tar.bz2#showconsole-1.08/blogd.c
>
> (void)ioctl(0, TIOCCONS, NULL); /* Undo any current map if any */
> if (ioctl(pts, TIOCCONS, NULL) < 0)
> error("can not set console device to %s: %s\n", ptsname,
>strerror(errno));
>
>so I suppose that's it. Write up a new program that calls the ioctl
>on a tty, and you should be done. IOW:
TIOCCONS only works for pseudo terminals.
Besides, it only redirects stuff you send to /dev/console. It
doesn't change what devices printk() prints to. Currently there
is no way to change that on a running kernel.
Mike.