Redirecting boot console RHEL5 and Xen

If your server/pc is recent enough to allow console redirection from the bios to a serial port or has a Fujitsu iRMC or ilo your need to change the /etc/grub.conf to allow bootup process to be monitored

Many manufactuers provide full console redirection at VGA resolution for an additional license fee around £200

But if you just want a serial redirection in an emergency you dont really new the full GUI especially if youve not install gnome Xwindows or KDE.
With text only display this should be available free of charge if you have iLO or iRMC or Sun XSCF

If you wanna use Redhat as the boot O/S you'll need to edit the grub.conf to enable the boot process to be displayed via a serial port ( tty)

in red hat rhel 5 , the example below shows com1 or tty0 redirection:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVolroot
# initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
serial --unit=0 --speed=57600 --word=8 --parity=no --stop=1
terminal --timeout=5 console serial
title Red Hat Enterprise Linux Server (2.6.18-128.1.10.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-128.1.10.el5 ro root=/dev/VolGroup00/LogVolroot console=tty0 console=ttyS0,57600n8 rhgb quiet
initrd /initrd-2.6.18-128.1.10.el5.img

then if you connect via ssh to irmc port or via https and open redirected console window


However if your booting Xen kernels you need to change further lines

title Red Hat Enterprise Linux Server (2.6.18-128.1.10.el5xen)
root (hd0,0)
kernel /xen.gz-2.6.18-128.1.10.el5 com1=57600,8n1
module /vmlinuz-2.6.18-128.1.10.el5xen ro root=/dev/VolGroup00/LogVolroot console=tty0 console=ttyS0,57600n8 rhgb quiet
module /initrd-2.6.18-128.1.10.el5xen.img

Hey presto you then get a output like below !

Starting anacron: [ OK ]
Starting atd: [ OK ]
Starting jexec: Starting jexec services[ OK ]
Starting background readahead: [ OK ]
Starting libvirtd daemon: [ OK ]
Starting Red Hat Network Daemon: [ OK ]
Starting yum-updatesd: [ OK ]
Starting Avahi daemon... Bridge firewalling registeredvirbr0: [ OK ]
Starting HAL daemon: [ OK ]
Starting xend: xenbr0: feature.peth0: Promiscuous mode enabled.[ OK ]
Starting RHN Managed Xen Domains:[ OK ]
Starting smartd: [ OK ]

Red Hat Enterprise Linux Server release 5.3 (Tikanga)
Kernel 2.6.18-128.1.10.el5xen on an x86_64


if you now would like to connect to com1 via a cable or have an interactive login on tty0 remotely add the following to the bottom of your /etc/inittab

# allow interactive shell or serial cable connection com1 (ttyS0)
S0:12345:respawn:/sbin/agetty -L 57600 ttyS0 vt100

Quite useful

Chris

infrasup helping Business in London with I.T support since 1990