Monthly Archives: March 2011

Migrate KVM Disk Access from IDE to Virtio

This article assumes a KVM guest that runs from raw or qcow2 devices using emulated ide access. Since some time now, full virtualisation for block devices is available, facilitating the benefit of paravirtualisation.

Benchmarked in bonnie++, the difference looks like this, revealing a way better performance of virtio:


Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
<host>          2G   856  94 33126   7 30392   7  4727  92 739753  70 300.4  20
Latency             51096us    2473ms     972ms    5240us    1516us     382ms
Version  1.96       ------Sequential Create------ --------Random Create--------
<host>              -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16    35   0 +++++ +++    46   0    34   0 +++++ +++    44   0
Latency               338ms     808us    2136ms     341ms     155us    2016ms


Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
<host>          2G   732  91 58767   8 72183  11  4026  94 1477698  80 321.6   9
Latency             16751us    1159ms     492ms    4155us     624us     422ms
Version  1.96       ------Sequential Create------ --------Random Create--------
<host>              -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16    34   0 +++++ +++    46   0    34   0 +++++ +++    45   0
Latency               240ms     790us    1502ms     296ms     167us    1450ms

So in order to make the switch from from ide to virtio, the following steps need to be taken:

Run virsh edit <your_vm_name>. From there, edit the config file and adjust all lines of

<target dev='hda' bus='ide'/>

so they look like this

<target dev='vda' bus='virtio'/>

Furthermore, remove all <address type .../> lines so that libvirt can regenerate them appropriately.

Inside the guest, edit /etc/fstab and replace all occurrences of /dev/sdX with /dev/vdX`.

That's it, now shutdown the machine and start it with an virsh start <your_vm_name> (just a reboot inside the started VM won't work).

Settin up a custom Weave Sync Server for Firefox 4



Starting with Firefox 4 it is really easy to keep your different Firefox browser setups at home, on your mobile or at work in sync. The Mozilla Corporation even hosts a central server for you so basically the setup can't be more easy.

Yet, if you're a little paranoid and you don't want to store your precious browser data on someoneelse's servers, you might wish for your own sync server. There are two posibilities to setup your own server: the Weave Minial Server and the full blown one.

Weave Minimal Server's development has been stopped now and is deprecated since shortly after FF4's relase. Therefore, this article documents the setup of the full server.

The chosen install location will be /var/www/weave. The article assumes a Mysql server for authentication installed locally. Further, a functional Apache 2 server is assumed with a fully configured SSL setup. The documentation was tested using an Ubuntu 10.10 setup.

Package Retrieval and Storage

A working installation of a full Weave server consists of of two packages: the Weave Sync Server and the Weave Registration Server. You may download and unpack the archives like this:

mkdir -p /var/www/weave/weave-synchronisation \
cd /var/www/weave && touch index.html
   tar xzf tip.tar.gz -C weave-synchronisation --strip=1 && rm tip.tar.gz
   tar xzf tip.tar.gz -C weave-registration --strip=1 && rm tip.tar.gz

In case the download links are deprecated, go and look for the according packages at their respective root directories: and

Note as of Oct 29, 2011: the links are deprecated as the whole sync-server gets an overhaul. The old version is still running smooth though, so the updated links are: and

Database Setup

Create a new database called weave containing the following tables:

CREATE TABLE collections (
  userid int(11) NOT NULL,
  collectionid smallint(6) NOT NULL,
  name varchar(32) NOT NULL,
  PRIMARY KEY  (userid,collectionid),
  KEY nameindex (userid,name)
  username int(11) NOT NULL,
  collection smallint(6) NOT NULL default '0',
  id varbinary(64) NOT NULL default '',
  parentid varbinary(64) default NULL,
  predecessorid varbinary(64) default NULL,
  sortindex int(11) default NULL,
  modified bigint(20) default NULL,
  payload longtext,
  payload_size int(11) default NULL,
  ttl int(11) default '2100000000',
  PRIMARY KEY  (username,collection,id),
  KEY parentindex (username,collection,parentid),
  KEY modified (username,collection,modified),
  KEY weightindex (username,collection,sortindex),
  KEY predecessorindex (username,collection,predecessorid),
  KEY size_index (username,payload_size)
create table users (
 id int(11) NOT NULL PRIMARY KEY auto_increment,
 username varchar(32),
 password_hash varbinary(128),
 email varbinary(64),
 status tinyint(4) default '1',
 alert text,
 reset varbinary(32) default null,
 reset_expiration datetime
) engine=InnoDB;

Now, create a user named weave in mysql with data permissions on the newly created Weave database. Remember the user's password for later.

Config Adjustments on Sync and Reg Server

To customise the configs of reg and sync portion of the full Weave server, two files have to be created before being edited:

cd /var/www/weave/weave-synchronisation/1.1 && \
   cp default_constants.php.dist default_constants.php
cd /var/www/weave/weave-registration/1.0 && \
   cp weave_user_constants.php.dist weave_user_constants.php
Adjustment of the Synchronisation Server

Now, edit /var/www/weave/weave-synchronisation/1.1/default_constants.php. First, adjust the mysql user's database password according to the previous step. Chanve weave to your own password there in the two line that say:

if (!defined('WEAVE_MYSQL_STORE_READ_PASS')) { define('WEAVE_MYSQL_STORE_READ_PASS', 'weave'); }

Next, adjust the size of maximum payload in the following line. I recommend just adding a zero to 262144:

if (!defined('WEAVE_PAYLOAD_MAX_SIZE')) { define('WEAVE_PAYLOAD_MAX_SIZE', 262144); } #256K

Now, uncomment the following line and insert a random character string where its supposed to:

#if (!defined('WEAVE_SHA_SALT')) { define('WEAVE_SHA_SALT', 'salt goes here'); }

You might also want to adjust the default quota from 5 MB to maybe 20 MB. Uncomment this line and adjust it:

#if (!defined('WEAVE_QUOTA')) { define('WEAVE_QUOTA', 5120000); } #5M
Adjustment of the Registration Server

The configuration file for the registration server is located at /var/www/weave/weave-registration/1.0/weave_user_constants.php. The following lines need to be customised. First, insert the mysql password by replacing the string weave:

if (!defined('WEAVE_MYSQL_AUTH_PASS')) { define('WEAVE_MYSQL_AUTH_PASS', 'weave'); }

Next, uncomment the salt line as before and insert the same character string as before for the sync server:

#if (!defined('WEAVE_SHA_SALT')) { define('WEAVE_SHA_SALT', 'salt goes here'); }

If you like to have user registration protected by captcha (I assume you do), get an account at and get yourself a global key. Adjust the following three line to suit your needs:

#if (!defined('RECAPTCHA_PUBLIC_KEY')) { define('RECAPTCHA_PUBLIC_KEY', '6LfWcwUAAAAAABnmLyhmgddYeJGdiRlo2MWSOpAl'); }

Apache2 Setup

This article assumes that you have your Apache 2 webserver SSL-secured and that you want the Weave server to be located at https://yourdomain.tld/weave/. Therefore, the following lines need to be inserted into your Apache 2 config (in Ubuntu that is /etc/apache2/sites-enabled/default-ssl):

# ----- weave-server -----------------------------------------------------------------

  Options Indexes FollowSymLinks
  AllowOverride none
  Order allow,deny
  Allow from all

Alias /weave/1.0 /var/www/weave/weave-synchronisation/1.1/index.php
Alias /weave/1.1 /var/www/weave/weave-synchronisation/1.1/index.php
Alias /weave/1.2 /var/www/weave/weave-synchronisation/1.1/index.php

Alias /weave/user/1.0 /var/www/weave/weave-registration/1.0/index.php
Alias /weave/user/1 /var/www/weave/weave-registration/1.0/index.php
Alias /weave/user /var/www/weave/weave-registration/1.0/index.php
Alias /weave/misc/1.0/captcha_html /var/www/weave/weave-registration/1.0/captcha.php
Alias /weave/misc/1/captcha_html /var/www/weave/weave-registration/1.0/captcha.php

Alias /weave /var/www/weave
# ----- /weave-server ----------------------------------------------------------------


service apache2 reload

to make the changes work.

Client Setup

To use your brand new Weave server in your shiny Firefox 4, choose Set Up Sync... from the Tools menu. There, you will need to create a new account and enter your server address (https://yourdomain.tld/weave/) in the server field after choosing the use of a custom server over Firefox Sync Server.

GnuDIP setup on Ubuntu 10.10


*[GnuDIP]: GNU Dynamic IP


This article briefly describes the setup of a dynamic dns-server, very similar to those commercial ones from and others. It will need access to the domain's zone file on the service provider's nameserver and will offer to manage dyndns-services using own domain names.

A specialty of the approach here is that a subdomain named ddns is added to yourdomain.tld. This results in dynamic names like home.ddns.yourdomain.tld, so that e.g. www.yourdomain.tld is still being managed by the nameservers of the service provider, as they usually offer a more failsafe service level.


This article assumes a running web-server for the GnuDIP's webfrontend as well as a mysql-server of version > 5. This documentation won't explain their setup in further detail.

The following Ubuntu-packages need to be installed:

aptitude install bind9 apache2 libapache2-mod-perl2 \
                 mysql-server dnsutils xinetd wget

Initially, the following lines have to be added to the zone file of the domain which supposedly managed by the service provider (not locally):

ddns                     IN NS      ns1.ddns
ns1.ddns                 IN A       {IP_of_the_ddns-server}

GnuDIP setup

This documentation stores the GnuDIP files in /opt/gnudip. Unpacking the GnuDIP sources, the archive actually stores the documentation in its root-folder, which is not very elegant. Therefore, in this article the doc-files go into a subfolder called doc whereas everything else will reside in GnuDIP's root folder /opt/gnudip.

Create a new directory for GnuDIP:

mkdir -p /opt/gnudip

Download the source package:

(cd /opt/gnudip && \

Unpack the archive in the recently created directory:

(cd /opt/gnudip && \
 tar xzf /opt/gnudip/gnudip-2.3.5.tar.gz -C /opt/gnudip --strip 2)

To me, the directory structure of the source package is a bit weird. That's why I reorder a little:

mkdir /opt/gnudip/doc
tar xzf /opt/gnudip/gnudip-2.3.5.tar.gz -C /opt/gnudip/doc --strip 1
rm -r /opt/gnudip/doc/gnudip

In /opt/gnudip/etc/ the new dns-update-keys have to be created for later use with bind9 nameserver:

(cd /opt/gnudip/etc && \
 dnssec-keygen -r /dev/urandom -a hmac-md5 -b 128 -n HOST gnudip-key)

This results in two files called /opt/gnudip/etc/Kgnudip-key.+157+{random_id}.key and /opt/gnudip/etc/Kgnudip-key.+157+{random_id}.private.

GnuDIP's configuration needs to know about the new private-file, so the following line in /opt/gnudip/etc/gnudip.conf has to be adjusted accordingly:

nsupdate = -k /opt/gnudip/etc/Kgnudip-key.+157+{random_id}.private

Database preparation

Given an adequately configured mysql-server, the file /opt/gnudip/doc/gnudip.mysql needs to be edited in order to become compatible with recent versions (5.*) of mysql-server:

(cd /opt/gnudip/doc && \
 sed -i "s/\(.*\)default '0'\(.*\)auto_increment,/\1\2auto_increment,/" gnudip.mysql)

Now, the password for the GnuDIP database has to be set in /opt/gnudip/doc/gnudip.mysql. The relevant parts are at:

grant select, insert, update, delete on gnudip           identified by '{your_password}';
grant select, insert, update, delete on gnudip@localhost identified by '{your_password}';

The same password has to be set in /opt/gnudip/etc/gnudip.conf at the line containing:

gnudipdatabase = {your_password}

Now, the mysql database and tables are created:

(cd /opt/gnudip/doc && mysql -p < gnudip.mysql)

Configuration of bind9 nameserver

The update-keys created earlier in GnuDIP's etc-directory have to introduced to bind9. Therefore, the key portion in /opt/gnudip/etc/Kgnudip-key.+157+{random_id}.key (cryptic string at the end of the file, assuming 8hmy3QYvyfLb8ZB3D5MHsf== here) is extracted and saved as /etc/bind/gnudip-key:

key gnudip-key {
      algorithm hmac-md5;
      // the TSIG key
      secret "8hmy3QYvyfLb8ZB3D5MHsf==";

A new zone-file for the dynamic domain has be created at /etc/bind/db.ddns{yourdomain.tld}. Beware not to mess with the dots:

$TTL 86400 ; default TTL (1 day)
@          IN SOA  ns1.ddns.{yourdomain.tld}. root.{yourdomain.tld}. (
                          0       ; serial
                          3600    ; refresh (1 hour)
                          1800    ; retry (30 minutes)
                          604800  ; expire (1 week)
                          0       ; TTL for NACK-s (0 seconds)
               IN NS    ns1.ddns.{yourdomain.tld}.
ns1            IN A     {your_ip_address}

Now, the key-file and the zone-file have to be introduced to bind9. Therefore the following lines have to be added to the end of /etc/bind/named.conf:

// include definition of GnuDIP update key
include "/etc/bind/gnudip-key";

// define GnuDIP dynamic DNS zone
zone "ddns.{yourdomain.tld}" in {
      type master;
      file "/etc/bind/db.ddns.{yourdomain.tld}";
      allow-query { any; };
      update-policy { grant gnudip-key subdomain ddns.{yourdomain.tld}; };

In order to create new journal-files for the dynamic domain, bind9 will need write access to its configuration directory:

chown bind /etc/bind

The nameserver now needs a restart:

service bind9 restart

A short test is useful in order to proof the correct implementation until now. First, the connection with the new ddns-nameserver is tested:

$ dig test.ddns.{yourdomain.tld}

; <<>> DiG 9.6.0-APPLE-P2 <<>> test.ddns.{yourdomain.tld}
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 58181
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;test.ddns.{yourdomain.tld}.        IN  A

ddns.{yourdomain.tld}.  0   IN  SOA ns1.ddns.{yourdomain.tld}. root.{yourdomain.tld}. 19 3600 1800 604800 0

;; Query time: 11 msec
;; WHEN: Sun Mar  6 16:38:22 2011
;; MSG SIZE  rcvd: 85

Now, the update function is tested:

$ /usr/bin/nsupdate -v -k /opt/gnudip/etc/Kgnudip-key.+157+{random_id}.private
> update add test.ddns.{yourdomain.tld}. 0 A
> $

Running the first command again should now resolve test.ddns.{yourdomain.tld} to

Configuration of Apache webserver

In this scenario, Apache 2 is used to serve the webfrontend for the GnuDIP admin as well as for its users. Also, access to web-application is supposed to run over a ssl-secured connection.

Activate ssl in Ubuntu's Apache (load module, activate ssl, restart daemon):

a2enmod ssl
a2ensite default-ssl
service apache2 restart

The following lines have to be added to /etc/apache2/sites-enabled/default-ssl:

RedirectMatch ^/gnudip(\/*)$ https://ns1.ddns.{yourdomain.tld}/gnudip/cgi-bin/gnudip.cgi
Alias /gnudip/html/ /opt/gnudip/html/
<Location /gnudip/html/>
    Options Indexes
    ReadmeName .README
    HeaderName .HEADER
    RemoveHandler .pl
    RemoveType .pl
    AddType text/plain .pl
ScriptAlias /gnudip/cgi-bin/ /opt/gnudip/cgi-bin/

Apache has to have access to the files above:

chown -R www-data:www-data /opt/gnudip

The initial admin-user is created using the following script:

/opt/gnudip/sbin/ -u {admin_name} {admin_password}

This user can now connect to GnuDIP's webfrontend available at:


Certainly, it is useful to reconfigure ns1.ddns.{yourdomain.tld} to something more memorable. The configuration options there are self explanatory and are not further documented at this point.

Apache needs a restart:

service apache2 restart

Configuration of xinetd

To be able to use update clients like e.g. ez-ipupdate a GnuDIP server on port 3495/tcp has be be set up. This is done by following these steps:

Introduction of port 3495 to the system is done by adding this line to /etc/services:

gnudip          3495/tcp

The file /etc/xinetd.d/gnudip has to be created with this content:

service gnudip
            flags       = REUSE
            socket_type = stream
            protocol    = tcp
            wait        = no
            user        = www-data
            server      = /opt/gnudip/sbin/
            bind        =

xinetd needs a restart now:

service xinetd restart

Client configuration

A valid update by ez-ipupdate may use the following command where [dyndns_name == username]:

ez-ipupdate -i {external_interface} -h {dyndns_name}.ddns.{yourdomain.tld} -S gnudip \
-u {username}:{password} -s {address_of_ddns-server}

Aside from the aforementioned client software GnuDIP comes with command line-based clients of its own in /opt/gnudip/client.

An elegant way of updating the dynamic dns entry is GnuDIP's "Auto URL"-function which offers a web-based update-method with an auth-cookie. Using this, a bookmark in a webbrowser can offer a shortcut to a quick IP-update. Also, commandline based browsers like w3m or elinks can be used to automatically update IPs where no ip-update-client is available.

Simple activation of SSL for Apache2 in Ubuntu 10.10

Just a few simple steps are necessary in order to activate ssl on apache-daemon in Ubuntu 10.10:

Load module:

a2enmod ssl

Activate ssl site config:

a2ensite default-ssl

Restart apache:

service apache2 restart 

Adjust the Number of Loop Devices

If you work intensively with virtualisation, vpns and other stuff that makes use of loopback-devices, the default number of 8 in distros like Debian and Ubuntu is pretty low. This article explains how to increase its number:

In /etc/modules change



loop max_loop=64

After that, run the following command:

for i in $(seq 0 63); do
    mknod -m0660 /dev/loop$i b 7 $i
    chown root.disk /dev/loop$i

Using vmbuilder with libvirt

In order to use vmbuilder (in my case python-vm-builder 0.12.4) to generate fully functional Ubuntu kvm-images, the following adjustments to the libvirt-template of vmbuilder have to be made in order to work.

First, make a dir-copy of /etc/vmbuilder/libvirt/ to a location that suits you and use it by handing over the --templates-option to vmbuilder.

The following lines of libvirt/libvirtxml.tmpl have to be changed:

#if $mac
#end if

has to be moved just in front of


The line

<graphics type='vnc' port='-1' listen=''/>

has to become

<graphics type='vnc' port='-1' listen='' keymap='de'/>

Add the following lines right before the closing devices-tag: