title: should I overwrite existing ssh key
body: <p>I was going to add ssh key for the machine I ssh so I do not have to enter password every time, but when I hit ssh-keygen I got this prompt </p>
  
  <p><code>Enter file in which to save the key (/Users/sanjeevkumar/.ssh/id_rsa):</code>
  I decided to accept I thought it will create new file mentioned in parentheses, but I got message saying 
  <code>/Users/sanjeevkumar/.ssh/id_rsa already exists.</code>
  <code>Overwrite (y/n)?</code></p>
  
  <p>now I am little cautious that where did the existing file come from and for what the existing file is storing the key for.</p>
  
  <p>If I choose to overwrite I don't want to be in situation where there tools stop working !</p>