[lug] boot failure with null modem between to machines

Scott Herod herod at dimensional.com
Tue Jun 22 23:15:09 MDT 2004

Hello all,

I discovered something a bit strange and I confess that I'm writing this
message partially because I couldn't find anything related while googling
around.  (I'm trying to squeeze in as many keywords as possible in case
this note helps someone else.)

I've got two machines each of which has a single serial port.  On these I
am running a slightly modified version of kernel 2.4.20-30.8.  In addition
I am using the heartbeat package from the Linux-HA project on these two
machines.  The Linux-HA package is not relevant to the boot failure but is
worth noting since I have a null modem cable connecting the two machines'
serial ports to support the heartbeat.

In my grub.conf file I had not used the console option to the kernel
command.  In /usr/src/linux-2.4/Documentation/serial-console.txt it says
that if you do not specify a console, the first device found will be used.  
It then adds that a VGA card is first looked for, then a serial port.  
I'm not sure that is the case.  With the serial cable connecting the two
machines I had strange behavior if I did not set tty0 to be the console.

In one instance one machine booted to the point that I could connect with
ssh.  The other machine was ping'able but would not accept connections
with ssh.  The machine that I could get onto was not logging the
/var/log/messages even though syslogd was running.  When I halted the
first machine I could no longer ping the second and ssh started reporting
no route to host rather than connection refused.

So, should anyone see something similar, try adding "console=tty0" to the 

        kernel /vmlinuz-2.4.20-30.8.legacy ro root=/dev/hda7 console=tty0


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