Specifications

The other log file, xend-debug.log , is very useful to system administrators since it contains

even more detailed information than xend.log . Here is the same error data for the same

kernel domain creation problem:

ERROR: Will only load images built for Xen v3.0

ERROR: Actually saw: GUEST_OS=netbsd, GUEST_VER=2.0, XEN_VER=2.0;

LOADER=generic, BSD_SYMTAB'

ERROR: Error constructing guest OS

When calling customer support, always include a copy of both these log files when contacting

the technical support staff.

6. Troubleshooting with the Serial Console

The serial console is helpful in troubleshooting difficult problems. If the Virtualization kernel

crashes and the hypervisor generates an error, there is no way to track the error on a local host.

However, the serial console allows you to capture it on a remote host. You must configure the

Xen host to output data to the serial console. Then you must configure the remote host to

capture the data. To do this, you must modify these options in the grub.conf file to enable a

38400-bps serial console on com1 /dev/ttyS0:

title Red Hat Enterprise Linix (2.6.18-8.2080_RHEL5xen0)

root (hd0,2)

kernel /xen.gz-2.6.18-8.el5 com1=38400,8n1

module /vmlinuz-2.618-8.el5xen ro root=LABEL=/rhgb quiet

console=xvc console=tty xencons=xvc

module /initrd-2.6.18-8.el5xen.img

The sync_console can help determine a problem that causes hangs with asynchronous

hypervisor console output, and the "pnpacpi=off" works around a problem that breaks input

on the serial console. The parameters "console=ttyS0" and "console=tty" means that

kernel errors get logged with on both the normal VGA console and on the serial console. Then

you can install and set up ttywatch to capture the data on a remote host connected by a

standard null-modem cable. For example, on the remote host you could type:

ttywatch --name myhost --port /dev/ttyS0

This pipes the output from /dev/ttyS0 into the file /var/log/ttywatch/myhost.log .

7. Paravirtualized Guest Console Access

Paravirtualized guest operating systems automatically has a virtual text console configured to

plumb data to the Domain0 operating system. You can do this from the command line by typing:

Troubleshooting with the Serial Console