Public-Key Authentication in SecureCRT

Public-key authentication is a proven, it’s better then allowing password authentication.As long as you keep your private key file safe, you’re less likely to encounter a break-in of your Unix/Linux servers. In this tutorial, I’ll try to show you the steps that you need to create public/private key using SecureCRT and use it with Ubuntu Server.

To create a public/private key pair in SecureCRT, open up SecureCRT, click on “Quick Connect“, from there click on the “Properties“:

Note: Uncheck all other options

Click “Create Identity File…” and the key generation wizard starts:

 Click “Next” to get started:

Select RSA as the Key Type and click “Next“:

Next, you are prompted to enter a passphrase twice (I leave it blank, but you should use something pretty long phrase, that you’re going to remember):

Next, it will ask you for your desired key length in bits. Take the default “1024” and click “Next“:

Now, you need to move your mouse randomly to generate some data to encrypt the key pairs:

Once it has been generated, click “Next” then you will need to save the public key and private key to your computer. Save it in a safe place!

Click “Finish” When asked whether or not you want to upload the following key, say NO!

Copy the public key into your home directory using WinSCP:

Login to your Linux server with your username and password and cat the content of the public key:

cat Identity.pub

First you need to format the public key properly, for this you need to delete the first four lines as well as delete the last line, and get JUST the key on a single line with “ssh-rsa” in front:

cat Identity.pub

Note: Open the file with “nano <public key filename>” and you will be able to edit it properly.

Create the “authorized_keys” file inside .ssh folder and set the permission on it:

touch .ssh/authorized_keys
chmod 750 .ssh/authorized_keys

Important Note: If .ssh folder doesn’t exist then you can use these command to create it!

mkdir ~/.ssh
chmod 700 ~/.ssh

Now that the RSA key is properly formatted, you can add it to the “authorized_keys” file.

cat Identity.pub >> .ssh/authorized_keys

Remove the public key (In this case, it is Identity.pub):

rm Identity.pub

Connecting via SecureCRT using your key pair:

If this is the same session you were already working with above, your identity file should already be filled in…if not, just click the browse button “…” and find your private key. Click “OK“. (You can also refer this link for more help):

It will not ask for the username and password

Hope this will help you!

Please Remember me in your prayers!

Enjoy 🙂

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Key-based ssh logins with PuTTY

Open your PuTTY Key Generator, it was installed when you installed PuTTY!

Click Generate:

You will need to move your mouse randomly to generate some data to encrypt the key pairs:

When the private/public key pair has been generated then you will need to save the public key and private key to your computer. Save it in a safe place!

Login to your Linux server with your username and password and enter the following commands:

mkdir ~/.ssh
chmod 700 ~/.ssh
nano ~/.ssh/authorized_keys2 

Paste the public key into your file. It may paste over in 3 lines, make sure its on a single line, this is very important!

Now to make that file accessible by only the user:

chmod 600 ~/.ssh/authorized_keys2

Now we shall create & save the session in PuTTY:

Select the Data and fill in the Auto-login username field, with the username for which you created the key:

We need to tell PuTTY to use a Private Key File. Select SSH->Auth-> Browse and point it to your private key:

Now we shall try to connecting via PuTTY using the saved session:

It will not ask for the username and password 🙂

Hope this will help you!

Please Remember me in your prayers!

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Time synchronization on Ubuntu 12.04LTS using NTP

To install the ntp, just enter this command at the terminal:

sudo apt-get install ntp

After installation, edit the default ntp configuration:

sudo nano /etc/ntp.conf

Commented out the default Ubuntu server,you can add your own time-servers here to synchronize with, http://www.pool.ntp.org/zone/europe or http://www.pool.ntp.org/zone/north-america lists:

After you are done with the configuration, just restart the ntp service:

sudo service ntp restart

To check if the NTP service is synchronizing:

sudo ntpq -c lpeer

To check the synchronization log:

sudo tail -f /var/log/syslog

Geeky Comparison with Windows clock after synchronization 🙂

Troubleshooting:

If you are using the firewall, then just allows port 123 on UDP level.

Hope this will help you!

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How to install Java 6 on Ubuntu 12.04

First, we will check that java is already install or not on our system:

java -version

As, we can see that the java is not install on our system, so we will downloads the Java binary installer from Oracle. (In this example, we will download & install the jre, but the procedure is exactly the same for jdk).

Transfer the downloaded file (jre-6u31***) to the Ubuntu from Windows machine using WinSCP.

Now, move to the directory where you copy the jre file(in my case, it is in tmp directory)

cd /tmp/

Give execute permission to jre file.

sudo chmod +x jre-6u31-linux-x64.bin

Run the jre file.

sudo ./jre-6u31-linux-x64.bin

After execution, it makes a new directory in the same location where jre file reside.

Move this newly created directory to /usr/lib/jvm/

sudo mv jre1.6.0_31 /usr/lib/jvm/

Enter this command:

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jre1.6.0_31/bin/java" 1

We are done!

Check the installed version of java.

java -version

Confirmation (Optional 🙂 ):

Here is a confirmation that we successfully installed the java on Ubuntu 12.04.

Hope this will help you!

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Step by Step tutorial to install Ubuntu Server 12.04

I hate to write the long articles, so I will make it short and sweet.

First, download the server version of Ubuntu from here,create the CD and boot the machine with the CD:

Once you successfully boot from CD, it will present you with the following screen in order to select your desired language and then press [Enter]

Select “Install Ubuntu Server”

Select the language, you would like to use for the install

Select your Country/City

It’s time to detect your keyboard layout. If you want to detect it then select “Yes” or else use the predefined one by using the “No” option.

Choose the Keyboard layout from pre-defined list

Choose a hostname for Ubuntu Server

Setting up username and password

It will show you warning if you are using the weak password

Select “Yes“, if you want to encrypted private directory (but I will use No)

If it finds the correct time zone for your location you can select Yes. If it says none or is not the time you wish to use, select No.

You have to partition your hard disk before use it, here I am using the “use entire disk” option

Configuring the package manager and select continue

Select how do you want to update your sever

Select the software that you wish to install by highlighting them and hitting the spacebar

Select Yes to install the grub in the master boot record

Installation complete message here, you need to remove the CD

After reboot, Login to the server by entering the username and password you created during installation

Hope this will help you!

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