IT ...

For GDM, SSH and local login,

local login,
/etc/issue

SSH,
/etc/ssh/sshd_config

Banner /path/to/file

GDM,
/etc/gdm/custom.conf (RedHat ...)
/etc/gdm/gdm.conf-custom (Debian ...)

[greeter]
DefaultWelcome=false
Welcome=Message for local users
RemoteWelcome=Message for remote login users




Create /etc/xen/scripts/network-multi-bridge

#!/bin/sh
dir=$(dirname "$0")
"$dir/network-bridge" "$@" netdev=eth0
"$dir/network-bridge" "$@" netdev=eth1

Change /etc/xen/xend-config.sxp

(network-script network-multi-bridge)