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Fedora Core 7 (FC7) Xen/KVM Guide
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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.

The Xen host must be setup for serial console output, and a remote host must exist to capture it. For the console output, set the appropriate options in /etc/grub.conf:

  • 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, install and set up ttywatch to capture the information on a remote host connected by a standard null-modem cable. For example, on the remote host:

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

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

Fedora Core 7 (FC7) Xen/KVM Guide
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