klibc - Nov 2007 - Netconsole capability in ramdisk

I'm supporting a number of consumer devices (e.g. small NAS devices)
in Debian.  They typically don't export the serial console and don't
have any other output devices.  We perform the installation via SSH
on such devices and start SSH automatically when the system boots so
people can login.  This works pretty well but sometimes a device stops
to boot for no good reason.  This is usually really hard to debug
since we don't have any logs at all.

For kernel messages, I could probably activate netconsole in the
kernel.  Even this is a bit tricky since we often cannot change the
kernel cmd line but I could probably use klibc in the ramdisk to setup
the network and then configure a dynamic netconsole.

My big concern is with userland messages, though.  I want to see what
the ramdisk is doing, ideally up to the login: prompt.  In other
words, I want to have everything sent to the serial console
broadcasted to the net.  I'm aware syslog supports remote logging, but
if I activate that I still wouldn't see what the ramdisk is doing.

Is there any way to solve this problem?
-- 
Martin Michlmayr
http://www.cyrius.com/

Martin Michlmayr wrote:
> I'm supporting a number of consumer devices (e.g. small NAS devices)
> in Debian.  They typically don't export the serial console and
don't
> have any other output devices.  We perform the installation via SSH
> on such devices and start SSH automatically when the system boots so
> people can login.  This works pretty well but sometimes a device stops
> to boot for no good reason.  This is usually really hard to debug
> since we don't have any logs at all.
> 
> For kernel messages, I could probably activate netconsole in the
> kernel.  Even this is a bit tricky since we often cannot change the
> kernel cmd line but I could probably use klibc in the ramdisk to setup
> the network and then configure a dynamic netconsole.
> 
> My big concern is with userland messages, though.  I want to see what
> the ramdisk is doing, ideally up to the login: prompt.  In other
> words, I want to have everything sent to the serial console
> broadcasted to the net.  I'm aware syslog supports remote logging, but
> if I activate that I still wouldn't see what the ramdisk is doing.
> 
> Is there any way to solve this problem?
Well, syslog() in klibc is actually writing to /dev/kmsg, which is 
equivalent to printk and any other kernel message.  Last I know, I don't 
believe netconsole supported /dev/console messages; this should probably 
be fixed.

	-hpa