linux-kernel - Re: serial console _after_ boot ?

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Date:	03 Jan 2008 17:55:02 GMT
From:	"Miquel van Smoorenburg" <miquels@...tron.nl>
To:	linux-kernel@...r.kernel.org
Subject: Re: serial console _after_ boot ? - was: Redirect kernel console

In article <Pine.LNX.4.64.0801031423070.26693@...rervta.pbzchgretzou.qr>,
Jan Engelhardt  <jengelh@...putergmbh.de> wrote:
>
>On Jan 3 2008 13:43, devzero@....de 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.
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