Attaching serial console on a Linux box

Step # 1: Setup Serial redirection

By default, grub output does not appear on the remote console; it only appears on the local terminal. However, you can configure your grub.conf file to redirect all grub output to the remote console. Redirection will display the grub output on the remote console, but not on the local terminal. To redirect grub output, make the following changes to your /etc/grub.conf file:


# vi /boot/grub/grub.conf
Append the following lines in the file

serial --unit=1 --speed=19200 --word=8 --parity=no --stop=1
terminal --timeout=8 console serial

* The first line tells GRUB to use the first serial port at a baud rate of 19200
* The second line gives the user 9 seconds to decide where GRUB should output it's information.
* Please adjust port number and speed as per your setup.

Next make sure splashimage options is disabled as graphics can't be displayed across the serial port. Remove splashimage line or just comment it out by prefixing # symbol:
#splashimage=(hd0,0)/grub/splash.xpm.gz

Also please comment out the hiddenmenu option ( We had some issues at times when tried using this, so to be on safer side,disable it )


Step # 2: Enabling serial output from the Linux kernel

Find the kernel line (grub config file) which corresponds to your currently running kernel. Add the following at the end of that line - console=tty0 console=ttyS0,9600n8:

title Red Hat Enterprise Linux ES (2.6.9-42.0.10.ELsmp)
root (hd0,0)
kernel /vmlinuz-2.6.9-42.0.10.ELsmp ro root=LABEL=/ console=tty0 console=ttyS1,19200n8
initrd /initrd-2.6.9-42.0.10.ELsmp.img


On Red Hat EL nodes, please make the following changes

* Set SAFE=YES in /etc/sysconfig/kudzu