This section provides some hints about how to solve common problems. It is not meant as an exhaustive step-by-step instruction, but should help get started with solving some issues.
The concept of networking has changed considerably from Xen2 to Xen3. Domain-0 is no longer directly connected to the bridge to prevent blocking of the bridge. Unfortunately, the initialization scripts of the system cannot handle the current configuration. To restart the network, run /etc/init.d/xend restart.
If the file system check did not work automatically, you may do it manually from Domain-0. Shut down your guest and run fsck on the image while it is not mounted. If fsck complains that the file system is mounted, check your mounts with the command mount.
DHCP needs several iptables kernel modules to run. Either those have not been installed or you updated your kernel and forgot to update the kernel modules in the guest system.
Connect your Xen machine to another workstation with a serial nullmodem cable. Then, on the Xen side, add the following parameter to the line
kernel (hd0,0)/boot/xen.gz com1=115200,8n1
Before you boot Xen, start a terminal program on your workstation. As an example, this may be
screen /dev/ttyS0 115200
Change the device and speed according to your needs.