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Fedora Core 6 Xen Virtualization Guide
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Serial Console - Host serial console access

For more difficult problems, serial console can be very helpful. If the Xen kernel itself has died and the hypervisor has generated an error, there is no way to record the error persistently on the local host. Serial console lets you capture it on a remote host.

You need to set up the Xen host for serial console output, and set up a remote host to capture it. For the console output, you need to set appropriate options in /etc/grub.conf, for example:

  • title Fedora Core (2.6.17-1.2600.fc6xen)
            root (hd0,2)
            kernel /xen.gz-2.6.17-1.2600.fc6 com1=38400,8n1 sync_console
            module /vmlinuz-2.6.17-1.2600.fc6xen ro root=LABEL=/ rhgb quiet console=ttyS0 console=tty pnpacpi=off
            module /initrd-2.6.17-1.2600.fc6xen.img

for a 38400-bps serial console on com1 (ie. /dev/ttyS0 on Linux.) The "sync_console" works around a problem that can cause hangs with asynchronous hypervisor console output, and the "pnpacpi=off" works around a problem that breaks input on serial console. "console=ttyS0 console=tty" means that kernel errors get logged both on the normal VGA console and on serial console. Once that is done, you can install and set up ttywatch (from fedora-extras) to capture the information on a remote host connected by a standard null-modem cable. For example, on the remote

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

Will log output from /dev/ttyS0 into a file /var/log/ttywatch/myhost.log

Fedora Core 6 Xen Virtualization Guide
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  Published under the terms of the GNU General Public License Design by Interspire