A Grub Question and some Grub Information
I set up a Debian serial console installation and am
going to add another Linux kernel to the list in
/boot/grub/menu.lst.
When looking at the boot paragraphs, I see an interesting
thing that I don't quite understand. Both the possible boot
methods have the savedefault line as their last line. Here they
are.
title Debian GNU/Linux, kernel 2.4.27-2-386
root (hd0,0)
kernel /boot/vmlinuz-2.4.27-2-386 root=/dev/hda1 ro console=ttyS1,9600n81
initrd /boot/initrd.img-2.4.27-2-386
savedefault
boot
title Debian GNU/Linux, kernel 2.4.27-2-386 (recovery mode)
root (hd0,0)
kernel /boot/vmlinuz-2.4.27-2-386 root=/dev/hda1 ro console=ttyS1,9600n81 single
initrd /boot/initrd.img-2.4.27-2-386
savedefault
boot
The savedefault line is supposed to determine which boot method
is 0 as far as I understand, so what do multiple savedefaults do?
Now, the behavior I discovered. After installing a
third paragraph to boot a test 2.6.5 kernel, I rebooted and
accidentally hit a key on the remote system that was connected to
the serial TTY on the headless box. What happened was that the
headless system came up with the recovery mode boot instead of
the first boot. I bet hitting any key to cause activity on the
serial port will cause this behavior because there is no serial
console alive at that point. I should have hit 0, 1, 2 or 3 on
the headless system. This behavior could be useful if it is
common. It could also be vexing if you had a serial line that
had some activity on it while a headless system was booting. I
remember how old Sun Sparc work stations using a serial console
would reboot if sent a break signal. Turning off the power to
the terminal sends a very long break.
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