After updating your centos, you might see the old kernel in the grub menu. This is how you remove the old kernel on centos (if you want to) :

  1. to ensure you really have old kernel installed, use rpm -q kernel to see it.
  2. Install yum-utils with yum install yum-utils
  3. remove it using package-cleanup --oldkernels --count=2. the --count option means how many kernels you want left

To make it always limited amount of kernels left after update, edit /etc/yum.conf and set installonly_limit. If you want always left 2 kernels then use installonly_limit=2

Minggu kemarin akhirnya dapat juga kesempatan pulang berbarengan dengan berbagai macam seminar. Ada GCOS (26-27 oktober), Richard M. Stallman speech (28/10 di BPPT & 29/10 di UI), kemudian diakhiri dengan idsecconf2009. Jadi, seminar-seminar itu cuma kedok supaya bisa pulang :D

Berangkat dengan gajayana new image pas dekat tengah malam. Sengaja menggunakan gajayana karena waktu tiba di Jakarta tidak terlalu pagi dan juga sekalian merasakan desain kereta terbaru hasil karya anak bangsa.

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Sebetulnya rada basi juga kalau nulis ini, gimana nggak sekarang aja ubuntu terbaru (9.10 a.k.a karmic koala) udah keluar :D

Modem yang kebetulan sedang saya pakai ini adalah huawei E1550 unlock dari operator 3 dan diisi sama “sapu”. Karena percobaan pertama tidak bisa langsung jalan si modem di jaunty, maka terpaksa mengkoneksikan dahulu si modem di windows kemudian tanpa di disconnect, restart masuk ke GNU/Linux dan langsung bisa dipakai.

Supaya bisa langsung tanpa masuk windows dulu ada beberapa langkah :

  1. Install terlebih dahulu udev-extras :
    sudo apt-get update && sudo apt-get install udev-extras
  2. Tambahkan rule udev kustom untuk modem :
    echo 'SUBSYSTEM=="usb", SYSFS{idProduct}=="1446", SYSFS{idVendor}=="12d1", RUN+="/lib/udev/modem-modeswitch --vendor 0x12d1 --product 0x1446 --type option-zerocd"' | sudo tee /etc/udev/rules.d/45-huawei1550.rules

Setelah semua selesai silahkan restart dan nikmati modem huawei E1550 anda ;)

Comparing gzip, bzip2, lzma
Most of you maybe never ever heard about lzma compression. It’s less popular than zip, gzip, or even bzip2. But how about 7-zip compression ?? yes, you may heard of it. It actually the famous implementation of lzma. After do some google, most of it says that lzma can reduce file size smaller than (even) bzip2. So it came to my curiosity comparing gzip2, bzip2, lzma.

Actually my will to compare lzma with gzip and bzip2 get stronger after my brother proved me that lzma can reduce file size smaller than bzip2. Well actually my brother only test it with 1 (one) pdf file, so I will prove it which can compress smaller. I will test it with text, image (png & svg), binary, movies and also mixed from all those files. And also I will use the best compression options.

The test machine is my sandbox machine. This is the spesification, and the :
debian etch 4.0 (2.6.18-6-xen-vserver-686)
2 x Intel Xeon Intel(R) Xeon(R) CPU 3040 @ 1.86GHz
1GB RAM (I have to shutdown all my domU to get 1GB back T_T )

The software version
gzip 1.3.5-15
bzip2 1.0.3-6
lzma 4.43-5

First Test (text files)

The first test is with a text file. For more dramatic I take the 2 files from my log files which has 656 MB and 60MB size. Well can you imagine how long the text will be with those size? :D . Ok here’s the test result :
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