Posted in Internet Stuff, Server

XEN 3.4 with ipv6 routing

Yes, there are a few postings out there about getting ipv6 routing running with XEN. But I’ll throw this online anyway since there are a few changes I had to make for it to work on my server. This text is intended for people who know their way around Linux and XEN so it will be a bit technical and won’t spell out every single step you have to make.

Most of the changes are based off scripts and information from BenV and wnagele (latter is interesting for me since I am also running XEN on a hetzner server). Have a look at the two links if anything is unclear. Now let’s start the fun 🙂

First of all we need IPv6 up and running on the host (dom0). Add the IP and gateway to your /etc/network/interfaces
This is what mine looks like:
iface eth0 inet6 static
address 2a01:4f8:100:1123::2
netmask 64
gateway 2a01:4f8:100:1120::1
pre-up ip -6 route add 2a01:4f8:100:1120::1 dev eth0

Check if the IP address is responding to the outside world (e.g. with, if everything looks ok, proceed …
Now we need to enable a few things to get routing and neighbor discovery running on the host (dom0). Edit your /etc/sysctl.conf and add/change these 2 entries (and while you are at it, set them with “sysctl -w” too):

So, your host should by now be online with ipv6 and soon be able to route packets to it’s guests. By default XEN will only take care of IPv4 when a guest is created, so here is a small patchfile that adds support for IPv6: xen-ipv6-vif-route.patch. The patch changes vif-route and, while these files may be in different places depending on your distribution, /etc/xen/scripts/ is where they can commonly be found. Download the patch to the directory with the scripts to be changed and execute a “patch -p0 < xen-ipv6-vif-route.patch” ( gets a few new IPv6 functions, and iptables now won’t try to change stuff for IPv6 IPs. vif-route changes are: ndp is enabled for the vif device and the route/neighbor IPv6 settings are set)

So, now that the scripts know how to setup all our IPv6 needs, we need to add the IPv6 IP to our guest settings (.cfg file typically found in /etc/xen/). What we want to change is the “vif” setting. Add the IPv6 IP of the guest to the IPv4 IP (just the IP without the trailing /network, space separated form the IPv4 IP):
vif = [ 'mac=B1:A3:3F:25:11:B8, ip=2a01:4f8:100:1123::5' ]

Now you can create the guest(domU) and add the IPv6 IP to the /etc/network/interfaces of the guest if you haven’t so already (it uses the host (dom0) as the gateway).

iface eth0 inet6 static
address 2a01:4f8:100:1123::5
netmask 64
gateway 2a01:4f8:100:1123::2

Restart the networking on the guest (or reboot it) and you should now be able to ping the guest from the internet. See, easy wasn’t it 🙂

Posted in Server

back online

The hard drive crash threw me offline a few days due to strange problems with software raids, Xen and acpi. Turns out that using the latest Xen kernel from debian testing branch on a software raid only works of you don’t set “acpi=off” as a kernel parameter. If acpi is turned off, the script “scripts/local-top/mdadm” in the initrd can’t find the devices needed to mount the software raid … causing the whole boot process to come to a grinding halt.

If I find some time I’ll do some more tests, untill then my server will be running with acpi turned on

btw. the hard disk replacement was easy. after the new drive was popped in it was just a copy the partition table and add the partitions of the new disk to the raid

Posted in Internet Stuff, Server, Tech

XEN and Kernel update

Server is up and running again. This morning I finished the xen (3.4) and kernel (2.6.32) updates I prepared yesterday evening. The only pitfall I stumbled across, was that the kernel in the debian repository (2.6.26-xen) seemingly wasn’t compatible with the latest xen in the debian repository (system would hang while booting, I guess that’s what I get for using “testing”).

Anyway, anyone using “lenny” or “testing” and wanting to update xen; here are a few tips to make the transition a breeze:

  • The debian wiki is full of useful information regarding xen
  • has a current xen kernel (linux-image-2.6.32-bpo.4-xen-amd64) that works fine with xen 3.4, just follow the instructions on on how to add it to apt.
  • I had to deactivate the “vfb” (VNC console) setting in the domU config files to get my guests to boot, browsing the Internet I saw people having the same problem with the “dhcp” setting.
  • If you are planning on updating the guests kernels too (advised), remember to change the “kernel” and “ramdisk” settings in the domU config files accordingly

With these few points in mind, the update is a breeze.

Posted in Tech


Server was down for the last 6 hours due to me updating a few stuff that really really didn’t work out too well (grub, xen and kernel at the same time). I gave up and afer a few hours of work managed to revert back to the old configuration so I can recieve mail again till I figure out what went wrong. Server may be down tomorrow a bit too while I try to figure out what exactly broke and try to at least get grub and xen updated.