Category: Computers

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Howto make SSH listens on multiple port

Although it is a security risks, it is possible to make OpenSSH listens on multiple port.

To do that, you need to edit /etc/ssh/sshd_config file. and enable the “GatewayPorts” option.

AllowTcpForwarding no
GatewayPorts yes
X11Forwarding no
#X11DisplayOffset 10

Look for the line that contain “Port 22”, and uncomment it if necessary, and add additional Port line to enable OpenSSH to listen to other ports. Like this:

Port 22
Port 80
Port 1025

The example will enable OpenSSH to listen to port 22,80,1025 simultaneously. Don’t forget to restart SSH service to enable the change by running :

sudo /etc/inet.d/sshd restart

Warning: Running SSH on multiple port may cause security risk, you have been warned!

Recommended Reading

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How to change Linux I/O Scheduler during runtime

This post describes the steps on how to change the Linux I/O scheduler dynamically while running a Linux operating system. You can refer to the previous post on the explanation of the differences of Linux I/O schedulers.

I/O schedulers determine how disk read/write are managed by the Linux kernel. Changing I/O scheduler requires you to know the name of your block device. So assuming your disk drive is “sda”, you can change the I/O scheduler using this command.


sudo echo noop > /sysfs/block/sda/queue/scheduler

This will change “sda” disk scheduler to NOOP, which is suitable for SSD drive. To display the current i/o scheduler, you only need to run this command.

cat /sysfs/block/sda/queue/scheduler
anticipatory deadline cfq [noop]

Note that, you will need to run this command each time you reboot or switch on your machine. In order to make the change permanent, you need to edit /etc/sysfs.conf and add “block/sda/queue/scheduler = noop” at the end of the file.

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Debian: Force users to use more secure login password with pam_cracklib

One of the factor that makes your system easily crackable is the weak password. PAM cracklib forces users to choose stronger password by analyzing the password strength, length and entropy.

To enable pam_cracklib in Debian / Ubuntu operating system, you need to install libpam_cracklib:

sudo apt-get install libpam_cracklib

Then edit the “/etc/pam.d/common-password” file using your favorite editor. Then, add and uncomment the following line at the end of the file.

password required pam_cracklib.so retry=3 minlen=6 difok=3

difok determines the number of same characters that allowed to be present in the old and new passwords.

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Ubuntu: How to erase CD-RW/DVD-RW from Command-line

Here’s an easy way to erase CD-RW and DVD-RW from command-line in Ubuntu:

you only need to install ‘wodim’ package:
sudo apt-get install wodim
Then run:
wodim -scanbus
To search for the cdrw device in case if you don’t already know.

To erase the entire disk, run:
wodim dev=/dev/cdrom blank=fast

That’s all!

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Buzz!! – Yahoo like IM shake with Pidgin Nudge plugin

I think most of you may have already migrated to Empathy, the default Instant Messenger client for the GNOME desktop environment. But I still use Pidgin IM because I like its functionality and its expandable plugin architecture.

I am a Yahoo Messenger user, and one thing that I miss about when using Pidgin (either on Linux or Windows) is the “shake-effect” whenever I receive “Buzz” or “ding” from my contacts. Back in 2003 (when Pidgin still was called Gaim) I tried replicating that effect, but to no avail. However, just a couple of weeks ago I discovered “pidgin-nudge“, a plugin that shakes conversation window when it receives “Buzz”,”nudge” or “ding” from contacts. Here’s how it looked :

Installing pidgin-nude on Ubuntu linux is easy! First make sure you have Pidgin 2.6.x and above installed. Then you have to install “pidgin-dev” package alongside with “build-essential” to compile the plugin source code, as shown in the example below.


sudo apt-get install subversion pidgin-dev build-essential
svn checkout http://pidgin-nudge.googlecode.com/svn/trunk/ pidgin-nudge-read-only
cd pidgin-nudge-read-only
make
sudo make install

Happy Buzzing!

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Microsoft Windows XP on vanilla AMD decTOP (Geode) – wished Linux GUI is this light

This is a continuation from my post of running Android on my AMD decTOP machine.

Of all Linux distribution that I tried, I found out that only Puppy Linux offered a usable GUI desktop environment on a plain vanilla AMD decTOP out of the box, but that is not without some effort on the installer side.

On the other hand, it is very easy to get Windows XP running on a plain vanilla AMD decTOP, without additional hardware upgrades. Here is my prove.

It seems Windows XP is more tolerant to low end desktops (or in this case, decTOP) than Linux operating system for fully GUI environment. Are we getting bloated?

AMD decTOP specs
RAM: 128MB RAM DDR2
HDD: 10GB IDE
Processor: AMD Geode GX 500, 366 MHz clock rate