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Ubuntu 11.04 Natty Narwhal Countdown Graphics
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.
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!
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
Play Urban Terror, a free Counter-Strike like game on Linux
Right now I’ve been playing Urban Terror (or UrT), it is a First Person Shooter (FPS) game similar to Counter-Strike. The game was developed using the open source Quake III Arena engine and can be played under GNU/Linux, Microsoft Windows and Mac OS X operating systems.
You can download Urban Terror binaries from Urban Terror Official Website
The game is available for 32bit and 64bit platform and is tested on Fedora 13 and Ubuntu 10.10 (Maverick Meerkat) releases
How to Setup SSH public-key or password-less authentication in Ubuntu
Here’s how to setup public-key (or passwordless) authentication in Ubuntu or any other Linux based operating system that use OpenSSH.
First make sure you’ve remote SSH server running and accepting connection. Then you need to generate ssh key on local server (I prefer RSA). You can enter passphrase for added security, or leave it blank for passwordless authentication.
local:~$ ssh-keygen -t rsa
Enter passphrase (empty for no passphrase):
The command will generate id_rsa and id_rsa.pub files. The files will be save in ~/.ssh/ directory. Then copy id_rsa.pub file to the remote server using SCP. Read How to use SCP on Linux or other UNIX-based Environment for more information about SCP
local:~$ scp id_rsa.pub username@remote.host:~/
Then you have to connect to the remote host and append the id_rsa.pub public key file to the list of “authorized_keys“. Don’t forget to chmod the authorized_keys file and .ssh directory, or OpenSSH won’t work correctly
local:~$ ssh username@remote.host
#now we are on remote server!
remote:~$ cat id_rsa.pub >> ~/.ssh/authorized_keys
remote:~$ chmod 644 ~/.ssh/authorized_keys
remote:~$ chmod 700 ~/.ssh
Make sure you have edited the “/etc/ssh/sshd_config” file to allow Public key authentication and RSA authentication.
#sshd_config file
PermitRootLogin no
...snip...
RSAAuthentication yes
PubkeyAuthentication yes
...snip..
Save and restart sshd server daemon by running the following command.
remote:~$ sudo /etc/init.d/ssh restart
After that, logout from the remote host to test the Public-key authentication
remote:~$ exit
local:~$
Testing the SSH public-key authentication
To test the public-key authentication, simply connect to remote server normally using ssh, and if things have gone smoothly you’ll be prompted to enter your passphrase, instead of password.
local:~$ ssh username@remote.host
Enter passphrase for key '/home/username/.ssh/id_rsa':
Note that you will not be prompted to enter passphrase/password if you’ve generated a key with “blank passphrase“, effectively making your login “passwordless”. For added security, it is advised that you disable normal interactive-keyboard password option and rely fully on public-key authentication by changing sshd_config line from:
PasswordAuthentication yes
to
PasswordAuthentication no
p/s: this tutorial was adapted from Shortest passwordless ssh tutorial, ever with updated notes for latest OpenSSH release