Ever needed to access a partition inside a block device not supporting partitions like /dev/loop or software raid? There exists multiple solutions like specifying the offset via losetup or patching the kernel. But this is error-prone and not very user friendly.

An easy and more user friendly way of supporting partition tables in any block device is kpartx. Besides the name, is has nothing to do with kde but is a tool from multipath tools to map partition tables to the device mapper.

After you installed kpartx you can easily create mappings from a block device with kpartx -a and delete them via kpartx -d. For example:

# echo p | fdisk /dev/loop0 
Command (m for help): 
Disk /dev/loop0: 102 MB, 102400000 bytes
255 heads, 63 sectors/track, 12 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

      Device Boot      Start         End      Blocks   Id  System
      /dev/loop0p1               1           5       40131   83  Linux
      /dev/loop0p2               6          12       56227+  83  Linux

# kpartx -a /dev/loop0
# ls /dev/mapper/loop0p*
/dev/mapper/loop0p1  /dev/mapper/loop0p2
# kpartx -d /dev/loop0
# ls /dev/mapper/loop0*
ls: cannot access /dev/mapper/loop0*: No such file or directory

To make a long story short: kpartx is a easy and handy solution for using partitions from any block device under linux making management of images for virtual machines quite simple.]]>

discussion on debian planet about installing Centos/Fedora to an directory under debian.
As mentioned in the comments and another blog entry there exist several other simpler solutions.

febootstrap allows you to install centos/fedora really easily just like deboostrap.
Example to install centos in directory c5:

# febootstrap centos-5 c5 http://mirror.eunet.at/5.3/os/i386/
# .....
# chroot c5 cat /etc/redhat-release   
# CentOS release 5.3 (Final)

mach is another more generic way to bootstrap rpm based distributions to a directory. For an overview of the features just have a look at the README Example to install centos:

$ mach -r centos-5-i386-os setup base 

If you just want to install Fedora/Centos into some directory use febootstrap as it is quite simple and does the job.
But if you want to rebuild rpms or bootstrap any other rpm based distribution like SuSE, Yellowdog use mach

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unattend-upgrades is a debian package providing automatic security upgrades.

To use it, just install unattended-upgrades, modify /etc/apt/apt.conf.d/50unattended-upgrades to your needs like:

Unattended-Upgrade::Allowed-Origins { "Debian stable"; };

To automatically and unattended install security updates you also have to set

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";

in /etc/apt/apt.conf or in a file located in /etc/apt/apt.conf.d/ (I use /etc/apt/apt.conf.d/60security)
For further details have a look at /usr/share/doc/unattended-upgrades/README or https://wiki.ubuntu.com/AutomaticUpdates

Just setup unattended-upgrades and life becomes more easy as you dont have to remember to upgrade each of your machines.]]>

I just started to use libvirt and needed to have static ip assignment for some of the systems. Libvirt supports this but there is no documentation for this, a patch with documentation has just been send to the mailing list, but thats all (except the documentation in the *.c files ;-)

A simple example which assigns 192.168.122.2 to the host with the mac AA:BB:CC:DD:EE:FF:

<network>
  <name>sample</name>
  <bridge name='intbr0' />
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254' />
      <host mac='AA:BB:CC:DD:EE:FF' ip='192.168.122.2' name='foobar'/>
    </dhcp>
  </ip>
</network>

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mpris player

media mlayer remote interface specification, short mpris is a specification to connect media players via dbus. This is quite useful as you can have one command for example to control Amarok, Audacious or any other mpris capable player.
This are all gui player, so lets have a look at mpd, a music daemon simple to control via commandline.
mpd natively does not support dbus, but there is another solution, mpDris, a mpd client exporting the mpris functionality via dbus.

mpris client

A really nice and powerful mpris command-line client is mpris-remote to access an mpris capable player. Here are some examples commands:

mris-remote pause # toggle pause 
mris-remote next # next 
mpris-remote random true 
mpris-remote random false 

it is really intuitiv, so just use ist.

So what is the benefit?

• You only have one command to control them all, so you can just switch your music player and your scripts will work. So instead of binding player specific commands to, e.g. your multimedia keys on the keyboard, consider using mpris and it does not depend if you use mpd, amarok, audacious or any other client.
• Additional features are possible, for example inhibit power-manager when playing music, so you can close the lid, unhibit when music stop so your pc can start sleep. And this works for multiple player out of the box.
• You can can subscribe to signals from the music player, so you can just get the information and don't have to check the status regular

So, if you going to control a music player via commandline, look if the player support mpris and use this, instead of proprietary command line.

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