Linux kernels can output information to serial ports. This is useful for debugging kernel panics and hardware issues with video devices or headless servers. The subsections in this section cover setting up serial console output for machines running Red Hat Enterprise Linux virtualization kernels and their virtualized guests.
27.12.1. Serial console output for the hypervisor(domain0)
By default, the hypervisor's serial console is disabled and no data is output from serial ports.
To receive kernel information on a serial port modify the /boot/grub/grub.conf file by setting the appropriate serial device parameters.
If your serial console is on com1, modify /boot/grub/grub.conf by inserting the lines
com1=115200,8n1
,
console=tty0
and
console=ttyS0,115200
where shown.
title Red Hat Enterprise Linux 5 i386 Xen (2.6.18-92.el5xen)
root (hd0, 8)
kernel /boot/xen.gz-2.6.18-92.el5
com1=115200,8n1
module /boot/vmlinuz-2.6.18-92.el5xen ro root=LABEL=RHEL5_i386
console=tty0
console=ttyS0,115200
module /boot/initrd-2.6.18-92.el5xen.img
If your serial console is on com2, modify /boot/grub/grub.conf by inserting the lines
com2=115200,8n1 console=com2L
,
console=tty0
and
console=ttyS0,115200
where shown.
title Red Hat Enterprise Linux 5 i386 Xen (2.6.18-92.el5xen)
root (hd0, 8)
kernel /boot/xen.gz-2.6.18-92.el5 com2=115200,8n1 console=com2L
module /boot/vmlinuz-2.6.18-92.el5xen ro root=LABEL=RHEL5_i386 console=tty0
console=ttyS0,115200
module /boot/initrd-2.6.18-92.el5xen.img
Save the changes and reboot the host. The hypervisor outputs serial data on the serial port(com1, com2 or other port) you selected in the previous step.
Note the example using the com2 port, the parameter
console=ttyS0
on the
vmlinuz
line us used. The behavior of every port being used as
console=ttyS0
is not standard Linux behavior and is specific to the Xen environment.
