tcpdump presentation

Balyya interview with NDTV

Listen.... nobody plays with balayya.....
Pretty old new but worth watching.

SSH login without using password.

Aim:-

You want to use Linux and OpenSSH to automize your tasks. Therefore you need an automatic login from host A / user a to Host B / user b. You don't want to enter any passwords, because you want to call ssh from a within a shell script.
How to do it

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

Steps :-
a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password:

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password:

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B hostname


A note from one of our readers: Depending on your version of SSH you might also have to do the following changes:

* Put the public key in .ssh/authorized_keys2
* Change the permissions of .ssh to 700
* Change the permissions of .ssh/authorized_keys2 to 640

Using expect script inside shell script

Written small sample shell script which contains expect script, which connect to ftp server.

SCRIPT:-

#!/bin/sh
echo "shell script starting"
ls
sleep 2
pwd
sleep 2
clear
echo "expect is starting"
expect -c "
spawn ftp 192.168.0.250
expect ":"
send \"user_name\r\"
sleep 1
expect "Password:"
send \"user_passed\r\"
sleep 1
expect "ftp\*"
send \"bye\r\"
sleep 1
expect eof"
echo "expect ended bash script follows"
ls -l
sleep 1
pwd
sleep 2