github.com and SSH keys

github.com access needs SSH keys permission. Here I list the process of generating ssh-key between my Unbuntu desktop and github.com remote server. Quite easy.
In my Unbuntu desktop:

$ cd $HOME

# If ssh-keygen command doesn't exist, you need to apt-get install.
$ ssh-keygen -t rsa

# a new directory .ssh is generated.
cd $HOME/.ssh

There are 2 files generated in .ssh directory.

1. id_rsa
   This is private key file which is kept locally
2. id-rsa.pub
   This is the file need to sync in github.com and locally.

Now copy contents in $HOME/.ssh/id_rsa.pub, and paste it in github: https://github.com/settings/ssh: Title: could be any string
Key: copy the above context to here and save.
After the authenication, now the following works:

$ git remote add origin git@github.com/account_name/repository_name.git
$ git push -u origin master