Compacting a Virtualbox image

Posted by coldtobi | 11 Oct, 2009, 20:06

My Laptop is on the move: I finally decided to reinstall it as a consequence from a self-inflicted filesystem crash. But this is also a good chance to switch filesystems. This was also already on my list for some time.

While coping all data to a safe place, I tried to figure out how to compact the Virtual Box image I use once in a while -- as its containing XP guest bloated during its lifetime. So when doing the autumn cleanup, why I shouldnt also try to clean up that to?

Disclaimer: The instructions are conserving space very aggressivly. You should not follow them if you are unsure what you are doing.  Repeat: No safety pins attached! It may explode right into your face! You did backup, right?

With some help of google, here are the instructions to shrink a vdi, the image containing the guest Windows XP:

1. Merge all snapshots (optional, but for best results you should do it).Note: Click the topmost "parent" snapshot and use "discard snapshot" to actually merge all together.....)

2. Start the Guest XP and clean it up:

  • Remove all unused programs.
  • To see space-hogs, use a tool like WinDirStat. If you see that there are programms you need seldom but takes lots of space, consider "compressing" it (Can be enabled on the files property dialog, "advanced settings")
  • Remove all Service-Pack and Windows Update folder (In the Windows directory, something like $NTServicePackUninstall$ or $NTUninstallKB<number>) Check Google for detailed instructions. 
  • Empty the trash can
  • Disable suspend-2-disk (hibernate) and virtual memory
  • reboot the guest
  • Defrag the guests' drive. Do it twice.
  • Use nullfile (get it here) to fill unused sector with "easy to compress" zeros.
  • Turn on again virtual memory and hibernation support. 
  • Turn off the guest OS

Now, the vdi is ready to be compressed. 

Start a shell and execute this command to complete the operation:

VBoxManage modifyhd <path-to-your-VDI> compact
(for me its: VBoxManage modifyhd /home/tobi/.VirtualBox/VDI/WindowsXP.vdi compact)


Beware: This takes some time. So do not use it if you are in a hurry or on battery power ;-)

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OpenSSH 0day?

Posted by coldtobi | 21 Jul, 2009, 22:55

Agroup called (or telling to be) anti-sec claims that they have a 0-day for OpenSSH. (

But that the 0-day exists is doubted. (

We'll see...

(Note: be warned when reading full-disclosuer: There is a fake exploit "Open0wn" which is in fact a trojan-horse, tricking to run under root. It will then spawn a botnet and delete your filesystem. Never run and compile exploits unchecked!)


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Posted by coldtobi | 7 Jul, 2009, 19:14

"" was a project that helpes Webmasters to ensure their privacy: In Germany you have to put a phone number on your site (or you might get sued). And "Einmalnummer" (translated one-time number) was perfect to protect your privacy, as no call center was able to use that number that fast.

But these times are gone: It seems that a governmental agency (the one responsible to regulate telecommunication -- The Bundesnetzagentur) had objections against the services....


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Thecus N2100: Testing kernels

Posted by coldtobi | 1 Jul, 2009, 23:40

Some time ago, I wrote how to test a kernel on the Thecus (here).

As I did not update the kernel for some time, I decided  to update to 2.6.30. As usual, I wanted to try it before flasing it permanently. To enforce this, I do not have the package "flash-kernel" installed. But unfortunatly, this time the testing method did not work or the kernel did not boot...


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Solarpowerlog released

Posted by coldtobi | 16 Jun, 2009, 21:12

Yesterday I made my initial release for solarpowerlog. Solarpowerlog is an application designed to keep track about photovoltaic systems.

It is desigend as an framework to be as much extenbile as possible. 

Currently it does support to connect to sputnik engineering "Solarmax" Inverters over TCP/IP, but the framework is designed to be easily expanded to support other types of inverters too.

So here are some links for the interested:


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Libucommon for debian

Posted by coldtobi | 11 Jun, 2009, 22:00

During my recent programming on solarpowerlog, I discovered that  the Lib Common C++ seems to have some bugs, at least in the TCPStream class. (bugreport)

So I decided to check its supposed succeedor. But this one is not packged for debian.... (RFP pending)

Short stort: Here it is.


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Mini trick: Don't show printers in samba shares

Posted by coldtobi | 19 May, 2009, 22:24

To help Windows understanding, that your local samba server does not support a printer, add to your smb.conf in the [global] section

    disable spoolss = yes

Reload samba, add it will vanish ;-)

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