I've got some systems that have serial devices attached; when these systems boot, the serial device may be sending data, so GRUB sees this, assumes it's a request to manage the boot process, and sits at the "choose a kernel" menu until someone manually connects to the server and continues the boot process. This is obviously not optimal.
How can I tell GRUB to ignore this serial port during the boot process? I currently have this in my /boot/grub/menu.lst (as an excerpt):
serial --unit=1 --speed=115200 --word=8 --parity=no --stop=1
#terminal --timeout=5 serial console
default=0
timeout=5
password --md5 <redacted>
hiddenmenu
title CentOS (2.6.32-642.3.31.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-642.3.1.el6.x86_64 ro root=UUID=<blah> rd_NO_LUKS KEYBOARD_TYPE=pc KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD nodmraid SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_NO_LVM rd_NO_DM quiet console=tty0 memmap=4128M$4096M
initrd /initramfs-2.6.32-642.3.1.el6.x86_64.img
I've just today added the top two lines but neither changed the behavior (even when the second wasn't commented out).
Is it possible to prevent that serial device from "hanging" the boot process without setting the timeout to 0?
Additional detail
Using terminal serial works, but doesn't show the grub menu at all, which prevents us from being able to interrupt the boot sequence in case single user is required.
Using terminal serial --timeout shows the menu, but hangs waiting for input.
Using terminal serial console shows the menu, but hangs waiting for input.
