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

net.ipv6.conf.all.forwarding=1
net.ipv6.conf.all.proxy_ndp=1

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 vif-common.sh, 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” (vif-common.sh 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::5 188.40.34.101' ]

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

This little script takes an IP or hostname as a parameter, and if there is an offending key in the .ssh/known_hosts it removes it and replaces it with the current valid one useful if you are moving/reinstalling a large amount of servers …

#!/bin/bash
#===============================================================================
#          FILE:  ssh-cleankey.sh
#         USAGE:  ./ssh-cleankey.sh <ip|hostname>
# 
#   DESCRIPTION:  deletes stale ssh known_hosts entries
#===============================================================================
 
# true or fasle
VERBOSE=false
 
#=== Exit codes ================================================================
# 1 - Not a valid IP or not reachable
#===============================================================================
 
#===  FUNCTION  ================================================================
#          NAME:  print_help
#   DESCRIPTION:  Prints help and exits
#===============================================================================
print_help() { #{{{
	echo "Usage: `basename $0` <ip|hostname>"
	echo ""
	echo "e.g. ./`basename $0` 1.2.3.4"
	echo ""
	exit 0
} #}}}
 
if [[ $# -eq 1 ]]
then
	HOST="${1}"
else
	print_help
fi
 
ping -w1 -c1 $HOST >/dev/null 2>&1
if [[ $? != 0 ]]
then
	$VERBOSE && echo "ERROR: $HOST is either not a valid IP/hostname, or is not reachable via ping"
	exit 1
fi
 
Check=$(ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true 2>&1|grep -c "Offending key")
if [[ $Check -gt 0 ]]
then
	$VERBOSE && echo "$HOST is stale, updating known_hosts"
	ssh-keygen -R $HOST >/dev/null 2>&1
	ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true >/dev/null 2>&1
else
	$VERBOSE && echo "$HOST is OK"
fi
 
exit 0

This is more a reminder to myself than anything else … this is small snippet that takes a list of IPs and does a whois on all that aren’t in a RBL

Lets say we have al list of IPs in a file “iplist.txt”:

12.172.121.171
24.149.208.68
38.105.100.9
58.185.207.86
61.201.51.66
64.78.164.169

Snippet that checks the IPs (can of course be easily changed to check IPs that are IN a RBL)

for ip in $(cat iplist.txt)
do 
  test $(/usr/bin/rblcheck -qm ${ip}) && continue || clear 
  whois $ip 
  printf "###########################\n##### %15s #####\n###########################\n" "${ip}"
  read
done

We did a bit of hiking through the forest to castle ruins yesterday, here are the pictures …

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panorama

Since the implementation of Arrays in Bash is somewhat lacking compared to higher level programming languages (only one-dimensional), and hash lists require a bit of work to set up, you may run into a situation where you have a small list of key/value pairs that are both variable and you need to store.
There are various solutions for the problem, e.g. creating two arrays (one for the keys, one for the values, and combining them by using the same index values for the entries), or using the functions from the link above to build a hash list. For me the easiest way to solve the problem, if I only have a few variables and don’t want to bloat the code, is to (mis)use declare. declare is intended for setting the type of a variable (constant, array, integer,…), but has the nice side affect that you can use variables in the key name, and you can set the value of the variable.

usage:

declare ${Key}=${Value}

Example:
$File_Config is variable holding the name of a configfile, the content of the file could look like this:

foo:one
bar:three
foobar:bignumber

Snippet:

if [[ -e "${File_Config}" ]]
then
  while read line
  do
    Key="${line%%:*}" # chop off everything after the first :
    Value="${line#*:}" # chop off everything before the first : 
    Value="$(echo ${Value}|sed 's#^ +##g;s# +$##g')" # chop off any excess whitespace
    if [[ "${Key}" != "" && "${Value}" != "" ]] # only continue if we have something to do
    then
      declare Configuration_${Key}="${Value}"
    fi
  done < "${File_Config}"
fi

after the snippet has read the configfile, you can use $Configuration_foo, $Configuration_bar and $Configuration_foobar in your script. The keynames could also have came from a mysql query, array, command line args, …

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

It seems that one of the hard drives in my server died last night. Thanks to the raid no data is lost, but the server will be offline shortly this week (tuesday morning probably) to replace the faulty drive with a fresh new one.

We shot over 600 photos on our cruise. Anyone who missed it on Facebook: we visited Savona (Italy), Barcelona, Palma de Mallorca (both Spain), Tunis (Tunisia), La Valletta (Malta), Cantania and Rom (both Italy). Anyway, here is a selection of some of the photos. Took me the better of the day to sort out which photos were worth while posting, and then post-processing them.

Savona

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Tunis

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Rom

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Palma de Mallorca

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Catania

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Barcelona

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La Valletta

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I always shoot in RAW + JPEG. For normal point-and-shoot vacation stuff I’m generally satisfied with the JPEG the camera spits out. But I would never shoot only JPEG. The additional information of RAW shouldn’t be underestimated, and to be honest I often tweak around. It makes a difference if you are working on the original RAW data, or if you are working on the JPEG copy the camera has already processed.
Up till now I’ve been post-processing my images with Adobe Bridge and Photoshop CS3. Since I was planning on post-processing a whole load of pictures I decided to see what software there is out there to streamline the work flow a bit (Bridge and CS3 do the job, and the raw converter in CS3 does offer a wide variety of options, but it is still tedious switching to be switching between both programs and working on multiple RAW images at the same time). While I was away, Adobe released Lightroom 3, so I checked out the reviews and it sounded good. I downloaded the 30 day trial version and to sum it up my experience so far … I’m impressed.
I haven’t worked with Lightroom previously, so I can’t say how much has changed in this version. But I really like the details that make life easier when handling collections of images. Being an Adobe product it also offers interfaces to various Photoshop functions (I only own CS3, I could imagine it offers more options if you have the current version CS5 installed). I could go on and on with things I like about it, but I’ll just sum it up and say: It really streamlines the work flow of post-processing photographs from import to print/upload/web/presentation and if you are shooting RAW it has a whole lot of fun stuff to play around with directly built in.
Since I shoot with a Nikon D80 that tends to produce a fair amount of image noise if I go past ISO 400 I liked the noise reduction features of Lightroom, both color and luminance noise can be reduced greatly with sliders for fine tuning.

It’s a good piece of software, and when the 30 day trial ends I’ll probably go buy it.

Ubuntu 10.04 (lucid) came out a short while ago … and because it contained new themes and the latest version of mythtv, I went and upgraded. These updates are tested by gazillions of people, any serious problems would be noticed before release .. right? right?

Well, looks like I did it again. Turned a working tv recorder into a “electronic beeping thing under the TV that doesn’t do much except show a pretty screensaver if you wait long enough”. After fixing up some stuff that the update broke (thanks for overwriting my config files. I’ll just use the version from the backup I made before the update if you don’t mind), I got almost everything up and running again. As of right now the only things broken are a) the theme not displaying any text when I’m in LiveTV or a video (yeah, try to get out of there without any menus) and b) my remote control is also not working.

At first I thought that some sonfig was just b0rked with the lirc config, but after doing a “top” and seeing that lirc_dev was consuming a modest 90% of my CPU, I decided that it was googles turn to find out what was wrong with Ubuntu 10.04. And sure enough, it seems this wa a know problem that made it into release (hooray). Anyone stumbling across this post via goole: go to https://bugs.launchpad.net/ubuntu/+source/lirc/+bug/550369, there are fixes for the problem towards the end of the page. Since it looks like they will make it into the 10.04 updates you can also just wait for a few days/weeks and they will pop up as a update automatically. Anyone wanting to fix the problem now: the short version ist: go to https://wiki.ubuntu.com/Testing/EnableProposed to set up proposed updates for lucid, and install “lirc” and “lirc-modules-source” from the proposed repository.

As for the broken themes? I’m still working on that, have a few updates and poking around to go before the system is back to the running condition it was before.

*Update*
For some strange reason, I had to set the IRQ of the serial port to 4 any specify it in the /etc/modconf.d directory (was getting busy errors with IRQ 3)

The broken themes were “only” the OSD using bold font. After changing it back to the normal version in the OSD settings everything worked fine.