How can we add packages in more than 400 servers
 

In a scenario if there are more than 400 servers what would be the best way to install packages in all the servers

There are several options...but you don't say what kind of servers you're dealing with, running what OS. Also, this question has been asked and answered on this site MANY times...the LQ search will help you find them.

Spacewalk is common, but depending on what your environment is, may not be a good fit for you. And honestly, this sounds like a homework question, like some of your other threads do:
http://www.linuxquestions.org/questi...ud-4175515055/
http://www.linuxquestions.org/questi...ge-4175513826/
http://www.linuxquestions.org/questi...on-4175510578/

maybe something like:

One place I worked had a simple cron job on each system... all it did was "yum update".

The local repository had the approved packages, so for any system the cron job did its work (once a week).

The log output was sent to the admin group, so every systems log was received.

As an added method, it was possible to use ssh to direct specific hosts to update at will.

http://unix.stackexchange.com/questi...administration

Maybe?

make a deb or a rpm if it is Debian or Redhat
and put it in your local repo

run CentOS and use: http://spacewalk.redhat.com/

If you want some additional automation, something like Puppet, CfEngine, or Chef would do what you wanted...

But How can That work be done manually without using automated tools like chef,puppet

How can you install a package on 400 different machines manually? Is this a serious question?

Go to each of the 400 machines, log in, and type 'yum install packagename' or 'apt-get install packagename' or whatever your distro's package manager requires.

You manually log in and perform the work. Either you use tools/scripts to do it, or you do it one by one, manually....you've been given package names and scripting advice on how to do things, so it's up to you to pick a direction.