Artur Hefczyc

 Have a look at this article about increased DDOS attacks on the services driven by the bot nets. In fact bot nets drive attacks but the real vehicles they drive are millions of Windows machines over the Internet.

Linux might be not the friendlies operating system yet. There are problems with hardware yet which make it difficult to use sometimes. But maybe defending yourselves and others from intruders is worth the extra effort. On the other side I am sure the more of us use the Linux the more hardware vendors add Linux drivers for their hardware.

Sometimes, when you change the Emacs version and you have own or custom Emacs packages installed and compiled with the previous version you may get unexpected behavior, including invalid function c-point warning message. The best solution for this is recompiling your *.el files using the current Emacs version:

Remove all old *.elc pre-compiled files:

find site-lisp/ -name "*.elc" -print | xargs rm -f

Recompile all Emacs source code files:

emacs --batch --eval "(byte-recompile-directory \"site-lisp/\" 0)"

The simple bash loop to do something with all files in the directory is:

for f in * ; do echo $f ; done

which just displays all files in this case.

This is easy, what I usually need and often forget how to do it is to execute some action exact number of times. Something like simple for loop in C or Java. And there is an exact match for such loop in Bash too:

for (( i=1 ; i<=100 ; ++i )) ; do echo $i ; done 

I found another similar solution on the Internet today at spiralbound.net:

for i in $(seq 1 100); do echo $i ; done

which might useful in some cases...

 I used to use KMail for years. It had some issues especially with IMAP accounts but worked fine for the most of the time and problems could be easily avoided by careful usage.

The Mail however in Mac OS X is completely different story. It is quite stable and better at using the IMAP accounts but it is consistently annoying in certain places.

Well, the installation went smooth and without any problems. I have made one mistake though. For some unknown to me reason I selected Mac UK keyboard as one of final settings. After restart there was no way to login or change the  settings. Now reinstalling Gentoo again.

Very short guide for those who are interested how to install Gentoo in less then 30 minutes:

1. Get the livecd-i686-installer-2007.0.iso or more recent image if it is available. Just make sure you download the full live CD not the minimal version.
2. Setup the virtual machine in VMWare and point it to the ISO image as an installation disk. After you finished setting it up VMWare tries to run it automatically. Don't let it to do so.
   • Depending on your needs set proper HDD size. It doesn't need to be very huge as you can always attach another virtual HDD later on. On the other hand HDD in VMWare starts at zero size and grows when it is needed up to the size you set. So in theory you can set quite huge size. I set 20GB for my installation.
   • I would recommend a least 1GB RAM. But again it depends what your are going to do with the Gentoo installed.
3. Stop it and go to settings and at least adjust memory settings. Defaults are usually quite low. I set 1.5GB for the Gentoo as my Macbook has 4GB.
4. Now, after you adjusted your all settings (in my case VMWare always crashes at least once) start virtual machine and let it boot from the ISO image.
5. The best and quickest way to install it is to use Networkless installation mode provided by the GUI installer. But before you run it I would recommend to setup partitions on your hard drive manually as the defaults offered by the installer are not the best for my preferences. My preferred layout (for private desktop, workstation) is: 100MB /boot partition, 2GB swap and the rest of hard drive for / - the rest of the system including home and var directory. On the server I usually set a separate partition for /home. Here is a step by step guide how you set partitions for your installation:
   • Browser menu: Applications -> Accessories and click Terminal
   • Terminal opens so set the root password to whatever you like using command: sudo passwd
   • When the new password is set switch to root user with command: su - and when asked enter the password you just set
   • Set your hard drive partitions with fdisk: fdisk /dev/sda
     • 'n' - creates a new partition, when asked what type of the partition to create answer 'p' - primary, and then press '1' - the first partition. It asks you for the first sector number, press Enter to accept default. It asks you then for the last sector number or the size of the partition, enter: +100M - 100 MB size as this is your boot partition.
     • 'n' - creates next partition, when asked about partition type answer 'p' (primary) again and press '2' - the second partition. Accept the default first sector and enter +2000M (2GB swap) as the size (last sector).
     • 'n' - creates your third and last partition, again 'p' for primary partition and '3' - the third partition. Accept the default first and if you accept the default for the last sector the rest of the whole hard disk will be allocated.
     • Change the second partition type from the default Linux to Linux swap by pressing 't' and then select the second partition by pressing '2' and when asked for the Hex code enter 82.
     • You can now press 'p' to display your partition table to make sure everything is set as it is expected.
     • 'w' to write your new partition table and exit fdisk.
   • Now you have to create filesystems on your new partitions:
     • mke2fs /dev/sda1 - creates ext2 filesystem on your /boot partition
     • mkswap /dev/sda2 - creates swap on your second, swap partition
     • mkreiserfs /dev/sda3 - creates Reiserfs file system on your third / the system partition

Now you can run Gentoo Linux Installer (GTK+) and if you select Networkless installation you have Gentoo system setup in less then half an hour.

Well, I am not really sure whether I install Linux on Macbook as a primary OS. However I miss the days when I used Linux as my development platform and there are some stuff in Mac OS X I just can't get used to.

So the day has come and I am installing Gentoo inside VMWare Fusion. The Macbook Pro has enough power to run both at the same time and with 4GB RAM on board there is enough for both systems. I hope this was I can use benefits from both worlds without sacrificing anything. On top of that I normally use 2 screens - one built-in the laptop and the second on the external monitor. This way I can use both system in full screen mode.

I tried both VM available for Mac OS X: Parallels and VMWare. I wanted to install amd64 Gentoo version. Parallels doesn't support 64bit systems at all so it lost at the beginning and it hang a few time so hard, I couldn't even kill -9 it. Well, this is something for OS to blaim for... VMWare claims it does. It even boots system from CD. During installation however it hangs too. The CD is not broken, nor the installation program is as www.tigase.org has been installed from this CD.

The Gentoo is installing right now in VMWare, let see how it goes...

I am generally happy with the Mac OS X installed on my Macbook. It is quite a good system and in most cases it works as expected.

Sometimes however it drives my crazy. I don't think this is a system created for software developers. At least not for software developers who work on the networking software.

I tried to do final tests over my Tigase Jabber/XMPP Server server and just couldn't do what I needed. One of the tests, called performance test, require sending 1000 messages over concurrent 1000 network connections between the Testsuite and the Tigase server.  Whatever I did, I couldn't successfully open more than 900 concurrent connections. I tried to play with numerous setting, like maximum opened files, file descriptors, tweaking TCP/IP settings, nothing helped.

On Linux I can easily manage to open 60k connections and all works fine without failure. I wonder whether this is kind of a hidden configuration parameter or maybe it is a desktop version of the Mac OS X feature and to open more connections I have to have server version...

Any suggestion or help with forcing Mac OS X to handle more network connections would be very much appreciated. Otherwise I will probably replace the nice system with the system which works...

I always wondered if the multi-core or hyper-threading technology is only marketing thing or ot really gives you a significant performance boost in your system. I mean home based system not in enterprise servers. Are all those core really used and given that you have a shared memory and a shared hard drive can you make use of all those cores.

I had to replace my old server which hosts all tigase.org services (websites, e-mails, Jabber/XMPP, SVN, project tracking....) as it couldn't cope with the load and it had too little memory. And as usually upgrading memory in old systems is much more expensive that buying memory for the new machine.

At the end I decided to build a new server from scratch. 64bits, 4GB RAM, 500GB HDD in Raid-1 and a CPU. I wasn't really convinced for multi-core so I thought for a moment about buying multi-cpu motherboard. I coulnd't, however find any non-Xeon multi CPU motherboards and XEON motherboards were quite expensive, don't even mention about CPUs.

Ok, I turned back to multi-core. Quad core was not so much more than Dual then I gave it a go.

Gentoo installation was quite smooth and suprisingly fast. Even though I've put -j5 option just in case to the make command didn't believe too much in it.

The compilation was so quick so I wanted to see what is the real gain from the multicore system. The best test as usual is the kernel compilation. I ran compilation with a single thread and then two threads, three, four, five and six. Below are results:

 Hm, colcusion: Number of CPU cores does really matter. Even in home based systems...

I have just experienced 2 weeks of Internet connection outage. That is really bad experience for a person who bases his work on the Internet technologies. But that was not the worse part of all.

The worse part was the support from the Internet provider side.

I called them every day to hear about the progress. For a few first days they were telling me different stories of what could happen. They tries to push the problem towards BT and asked me to do some phone line testing and so on...

After a few days one of the person from the technical team said: "Ah, there is some maintenance carried on in your exchange box. It may take up to 5 days...." Hm. First of all why they didn't tell me that on the first day? Actually there is a point in the "Terms & Conditions" document that in case of longer outages customer should be notified ahead of time of that event.

Of course nobody cared to notify me so just in case I called the technical support the next day. I was told that, indeed there is a maintenance carried on but usually customers doesn't get disconnected. A short connection drop may happen only. So I could be accidentally disconnected by the engineer and from now on my connection is flagged as faulty and engineer will looks at it in a few coming days. When? Maybe tomorrow but they have 6 days to respond for the issue.

I called again for next 2 days to hear exactly the same story. So at this point I stopped to believe anything would change in acceptable time. I ordered a business class Internet connection from a different provider on a second phone line and sent complaints to the old provider customer service and customer care. I have also sent an e-mail to the technical service in this provider.

In meantime I noticed the old provider charged my bank account for the next month of "their service". After 2 weeks I had enough. Nothing has changed. Every day the same story. I called this time customer care department to cancel my account and terminate the contract. It wasn't easy to get to them by the way. I was sent from one phone number to another 5 times before I could talk to somebody about canceling my account. I asked also for a refund for the time the service was not available to me and for the next month they already charged my account.....

This is the most "funny" part. They were very happy to process cancelation of my account but then... They said they won't refund me any money because I have just cancelled my account and I haven't given them a chance to fix the problem!

I have send a few complaints and I haven't received any response to them so far.... I have only received response from their technical service that the problem is now fixed. And indeed. Next day after I called to cancel my account the old connection started to work mysteriously. On the same day the new phone line has been installed and Internet connection from the other provider has been activated though.

I have written this story with all the details to warn you to keep away as much as possible from the Pipex Internet provider which has been just bought by Tiscali. Their technical support is a disaster. I wouldn't recommend it to my enemy. And the story is not over yet. I am still waiting for a response to my complaints....

 A few weeks ago I wrote an article about custom sorting order in SQL statement.

Today I tried to do the same in MS SQL Server. Obviously the solution described there didn't work as SQL Server has it's own ways to do things. It uses 'case' statement to define custom order. The query for SQL Server should look like this:

select Animal from animals 
order by case id
  when 3 then 1
  when 4 then 2
  when 10 then 3
  when 7 then 4
  when 9 then 5
  when 5 then 6
  when 6 then 7
  when 1 then 8
  when 2 then 9
  when 8 then 10
end;

The question which now arises is what happens if the 'id' is different from all possible values specified in the case statement? Well, the order for such a value is unspecified therefore the result is the same as if you specified else null after the last when. You can control it however and put there else 1000 after the last when. In such a case all cases not enumerated in the case will go to the end of the result lists and you can filter them out with top instruction:

select top 10 Animal from animals 
order by case id
  when 3 then 1
  when 4 then 2
  when 10 then 3
  when 7 then 4
  when 9 then 5
  when 5 then 6
  when 6 then 7
  when 1 then 8
  when 2 then 9
  when 8 then 10
  else 11
end;