Single Node Hadoop setup in Ubuntu 12.0.04 - linux

Question

I'm following the below steps to setup the ssh for running hadoop in single node, but, some how the when running sudo apt-get install openssh-server gives me an below exception trace, can any shed some light on this?
hduser#ubuntu:~$ sudo apt-get install openssh-server
[sudo] password for hduser:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package openssh-server is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'openssh-server' has no installation candidate
solutions tried:
1 # update and install, no luck
sudo apt-get update
sudo apt-get install openssh-server
2# which ssh, this not solution for this issue, but FYI,
which ssh gives below info,
hduser#ubuntu:~$ which info
/usr/bin/info
whereas,
which sshd gives no path,
hduser#ubuntu:~$ which sshd
hduser#ubuntu:~$
3 # fyi,
hduser#ubuntu:~$ ssh localhost
ssh: connect to host localhost port 22: Connection refused
hduser#ubuntu:~$
hduser#ubuntu:~$ ssh -vvv localhost
OpenSSH_5.9p1 Debian-5ubuntu1.1, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to localhost [127.0.0.1] port 22.
debug1: connect to address 127.0.0.1 port 22: Connection refused
ssh: connect to host localhost port 22: Connection refused

Answer 1

you can try below command from terminal for setting up ssh.
sudo apt-get install ssh