by Ramesh Natarajan
on June 26, 2008
I explained previously how to Perform SSH and SCP without entering password on openSSH. In this article, I’ll explain how to setup the key based authentication on SSH2 and perform SSH/SCP without entering password using the following 10 steps.
1. Verify that the local-host and remote-host are running SSH2. Please note that ssh and scp is a symbolic link to ssh2 and scp2 respectively as shown below.
[local-host]$ ls -l /usr/local/bin/ssh /usr/local/bin/scp
lrwxrwxrwx 1 root root 4 Mar 10 22:04 /usr/local/bin/scp -> scp2
lrwxrwxrwx 1 root root 4 Mar 10 22:04 /usr/local/bin/ssh -> ssh2
[local-host]$ ssh -V
ssh: SSH Secure Shell 3.2.9.1 (non-commercial version) on i686-pc-linux-gnu
[remote-host]$ ls -l /usr/local/bin/ssh /usr/local/bin/scp
lrwxrwxrwx 1 root root 4 Mar 10 22:04 /usr/local/bin/scp -> scp2
lrwxrwxrwx 1 root root 4 Mar 10 22:04 /usr/local/bin/ssh -> ssh2
[remote-host]$ ssh -V
ssh: SSH Secure Shell 3.2.9.1 (non-commercial version) on i686-pc-linux-gnu
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by Ramesh Natarajan
on June 23, 2008
I’ll be posting series of “Productivity Tips for Geeks” on a on-going basis targeted toward geeks who spend lot of time in front of the computer.
I hate to use the mouse and use keyboard intensively for all my work. If I perform a single action more than few times using mouse, I’ll try to find a corresponding keyboard shortcuts and use it. Using keyboard instead of mouse can be a immediate productivity booster for most of the people. In this post, let us review how to launch the frequently used software on your Windows operating system using keyboard.
One of my frequently used program is notepad++ and I don’t want to click on the “Start -> All Programs -> Notepad++ -> Notepad++”, every time I want to launch Notepad++. Following 5 steps explain how to setup the shortcuts and launch any software using keyboard quickly.
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by Ramesh Natarajan
on June 22, 2008
PERC/CERC Configuration utility from DELL is used to manage the disks on the server and perform several disk related activities. for e.g. Create Logical Volumes with different RAID options, check for the consistency of the disks etc.
During the server startup process, there is an option to Launch the PERC/CERC configuration utility. However sometimes it may be required to view the disk information or perform certain disk related operation without having to reboot the server. In this article, I’ll explain how to launch PERC/CERC configuration utility directly from the RedHat Linux.
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by Ramesh Natarajan
on June 18, 2008
If you are using SSH client to connect to Linux server from your Windows laptop, sometimes it may be necessary to launch UI application on the remote Linux server, but to display the UI on the windows laptop. Following are two typical reasons to perform this activity:
- Install software on Linux from Windows: To launch a UI based installer to install software on remote Linux server from windows laptop. For e.g. A DBA might want to install the Oracle on the Linux server where only the SSH connection to the remote server is available and not the console.
- Launch Linux X client software on Windows: To launch X Client software (for e.g. xclock) located on your remote Linux server to the Windows laptop.
Cygwin can be used to perform the above activities. Following 15 steps explains how to install Cygwin and launch software installers on Linux from Windows. Go to Cygwin and download the setup.exe. Launch the setup.exe on the Windows and follow the steps mentioned below.
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by Ramesh Natarajan
on June 15, 2008
If you are developing java application, it is important to understand that the java class files can be easily reverse engineered using java decompilers. In this article, let us explore how a java class file is reverse engineered and how to protect your source code from being reverse engineered by someone.
The java source code is compiled to a class file that contains byte code. Java Virtual Machine needs only the class file for execution. The problem is that the class file can easily be decompiled into the original source code using java decompiler tools. The best solution to prevent reverse engineering is to obfuscate the class file so that is will be very hard to reverse engineer. According to the dictionary Obfuscate means “to make obscure or unclear”. That is exactly what lot of java obfuscator tool will do as explained below.
I. Decompile Java class file.
Before understanding how to obfuscate the java code, let us first try to understand how someone can reverse engineer your java application. Following 3 steps explains how a class file is reverse engineered to the original java source code.
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by Ramesh Natarajan
on June 10, 2008
In this article, I’ll explain how to perform ssh and scp without entering the password using the SSH Public Key authentication with SSH Agent on openSSH
There are two levels of security in the SSH key based authentication. In order for you to login, you need both the private key and the passphrase. Even if one of them is compromised, attacker still cannot login to your account, as both of them are needed to login. This is far better than typical password based authentication, where if the password is compromised, attacker can gain access to the system.
There are two ways to perform ssh and scp without entering the password:
- No passphrase. While creating key pair, leave the passphrase empty. Use this option for the automated batch processing. for e.g. if you are running a cron job to copy files between machines this is suitable option.
- Use passphrase and SSH Agent. If you are using ssh and scp interactively from the command-line and you don’t want to use the password everytime you perform ssh or scp, I don’t recommend the previous option (no passphrase), as you’ve eliminated one level of security in the ssh key based authentication. Instead, use the passphrase while creating the key pair and use SSH Agent to perform ssh and scp without having to enter the password everytime as explained in the steps below.
Following 8 steps explains how to perform SSH and SCP from local-host to a remote-host without entering the password on openSSH system
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by Ramesh Natarajan
on June 8, 2008
“Treat your password like your toothbrush. Don’t let anybody else use it, and get a new one every six months” – Clifford Stoll
When you create an account on a website, you may have the “password dilemma” for a second. The dilemma is whether you should provide a weak password that is easy to remember or a strong password that is hard to remember. Following are the rules and guidelines that may help you in overcoming the password dilemma and help you in creating a strong password that are secure. These are the things that I’ve used over years based on my own interest in the area of keeping the password safe and secure.
I. Two essential password rules:
Following two rules are bare minimal that you should follow while creating a password.
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by Ramesh Natarajan
on June 5, 2008
This is a 16 step Fedora 9 Sulphur installation guide covering a typical installation scenario. I have shown the screenshots for some of the important installation steps below.
1. Install menu: This screen displays the install menu with the the following option. I selected the option 1 – Install or upgrade an existing system.
- Install or upgrade an existing system
- Install or upgrade an existing system (Text Mode)
- Rescue installed system
- Boot from local drive
- Memory Test
2. Test the media (CD): This screen lets you verify the installation media. I typically skip this step.
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My name is Ramesh Natarajan. I will be posting instruction guides, how-to, troubleshooting tips and tricks on Linux, database, hardware, security and web. My focus is to write articles that will either teach you or help you resolve a problem. Read more about