This is mostly a note to myself... After setting up a minimal Ubuntu server install (in Xen), following these instructions using debootstrap I saw lots of errors like this:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

Checking with locale -a would show

C
POSIX

While a full Ubuntu server install (off a CD) would show:

C
en_US.utf8
POSIX

This command seems to have generated the missing locale and made everybody happy.

localedef --no-archive -i en_US -c -f UTF-8 en_US.UTF-8

I've been experimenting with setting up Ubuntu Server 8.04 (Hardy Heron) to run Xen, and had a minor problem with UFW (Uncomplicated Firewall) running in the dom0 blocking network access to a domU running in bridged mode. It seems the fix is just to edit /etc/defaults/ufw and make this change to enable forwarding:

--- a/default/ufw       Thu Oct 23 10:00:33 2008 -0500
+++ b/default/ufw       Thu Oct 23 10:34:36 2008 -0500
@@ -16,7 +16,7 @@ DEFAULT_OUTPUT_POLICY="ACCEPT"

 # set the default forward policy to ACCEPT or DROP.  Please note that if you
 # change this you will most likely want to adjust your rules
-DEFAULT_FORWARD_POLICY="DROP"
+DEFAULT_FORWARD_POLICY="ACCEPT"

 #
 # IPT backend

and then run ufw disable; ufw enable.

I believe dom0 is now protected, and it'll be up the the domU to protect itself. I can't say I'm entirely comfortable with Linux IPTables, sure wish PF was available as an alternative.