Linux Tips and Tricks

Linux Tips and Tricks

Step by Step :: Password less ssh login

November10

First we will see, how to install the openssh in your ubuntu machine.

1) Type the below command in your console

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$ sudo apt-get install openssh-server openssh-client

2) Once it get installed, see whether you have the sshd dameon is running in your system or not.

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$ps -ef | grep ssh
root      3878     1  0 23:26 ?        00:00:00 /usr/sbin/sshd -D

3) Now you are ready to use the ssh connection. Lets test the ssh connection to the localhost itself.

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$ ssh localhost
The authenticity of host 'localhost (127.0.0.1)' can't be established.
ECDSA key fingerprint is 99:4c:e7:56:8e:ec:81:67:87:95:38:26:35:01:a1:e4.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
kamaraj@localhost's password:

Now provide the password for your user account. And it will get into the system (in this case its localhost)

4) How to set password less connectivity ?

5) create public key and private key for the host by using the below command.

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#Goto the home directory and execute the below ssh-keygen command
$ cd 
$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/kamaraj/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identificat ion has been saved in /home/kamaraj/.ssh/id_rsa.
Your public key has been saved in /home/kamaraj/.ssh/id_rsa.pub.
The key fingerprint is:
16:fc:a9:bc:d9:fe:f1:12:0f:05:88:04:b4:8c:5b:97 kamaraj@Kamaraj
The key's randomart image is:
+--[ RSA 2048]----+
|     .oo.. .     |
|     o o... .    |
|    . + E    .   |
|     o . o .  .  |
|    .   S o  .   |
|       o .  o    |
|        o   .+   |
|         +  .o.  |
|        o.o....  |
+-----------------+

6) Now you can see a .ssh folder is created in your home directory and you can see some files inside the .ssh folder.

Note : .ssh is hidden folder

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kamaraj@Kamaraj:~/.ssh$ ls -lrt
total 16
-rw-r--r-- 1 kamaraj kamaraj 1106 Nov 10 23:26 known_hosts
-rw-r--r-- 1 kamaraj kamaraj  397 Nov 10 23:28 id_rsa.pub
-rw------- 1 kamaraj kamaraj 1675 Nov 10 23:28 id_rsa
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~/.ssh/id_rsa : private or identification key
~/.ssh/id_rsa.pub : public key

7) create a new file called authorized_keys2 in .ssh folder and copy the contents of id_rsa.pub.

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cat id_rsa.pub >> authorized_keys2

8) That’s all. Now try the ssh command.

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$ ssh localhost
Welcome to Ubuntu 11.04 (GNU/Linux 2.6.38-12-generic i686)
 
 * Documentation:  https://help.ubuntu.com/
 
Last login: Thu Nov 10 23:48:00 2011 from localhost
$

This time ssh command didn’t ask the password.

If you want to connect to some other machine, then scp the id_rsa.pub file to the destination machine and put it under the .ssh folder in the name of authorized_keys2.

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