SSH Connection without password is not working - hadoop

Question

I am new to hadoop. Trying to connect namenode and data node through ssh. But I am not able to access ssh without password even though i have setup public key
Below is the sshd config.
# Package generated configuration file
# See the sshd_config(5) manpage for details
# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes
# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024
# Logging
SyslogFacility AUTH
LogLevel INFO
# Authentication:
LoginGraceTime 120
PermitRootLogin prohibit-password
StrictModes yes
RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile %h/.ssh/authorized_keys
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes
# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no
# Change to no to disable tunnelled clear text passwords
#PasswordAuthentication yes
# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no
#MaxStartups 10:30:60
#Banner /etc/issue.net
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
Subsystem sftp /usr/lib/openssh/sftp-server
# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
Please let me know how to fix the issue. I have tried several solution available in google but none of them are working. Please help

Answer 1

Try to follow these steps below.
Change to root user
arif#ubuntu:~$sudo -s
Recreate the SSH directory
root#ubuntu:~# cd ~
root#ubuntu:/# sudo rm -rf .ssh
root#ubuntu:/# ls -l .ssh
ls: cannot access .ssh: No such file or directory
root#ubuntu:/# mkdir .ssh
root#ubuntu:/# chmod 700 .ssh
Create authorized_key file
root#ubuntu:/# touch .ssh/authorized_keys
root#ubuntu:/# chmod 600 .ssh/authorized_keys
Generate a passwordless key
root#ubuntu:/# ssh-keygen -t rsa -P ""
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
/root/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
4f:f1:83:ad:03:ed:82:46:fa:11:ec:74:10:bf:03:41 root#ubuntu
The key's randomart image is:
+--[ RSA 2048]----+
| .E |
| + |
| o . . |
| . o o = |
| = S + + |
| = + * . . |
| . = . = |
| o . . . |
| . |
+-----------------+
Copy that key to other servers
Also, copy to localhost
root#ubuntu:/# cat /root/.ssh/id_rsa.pub >> /root/.ssh/authorized_keys
root#ubuntu:/# chmod -R 750 /root/.ssh/authorized_keys
Test your key
root#ubuntu:/# ssh localhost
###########################################################
# WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! #
###########################################################
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
87:21:89:ac:cd:ce:bf:32:30:d6:d2:a2:dc:ff:6d:ad.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /root/.ssh/known_hosts:1
remove with: ssh-keygen -f "/root/.ssh/known_hosts" -R localhost
ECDSA host key for localhost has changed and you have requested strict checking.
Host key verification failed.
Following the instructions mentioned in the above error
root#ubuntu:/# ssh-keygen -f "/root/.ssh/known_hosts" -R localhost
# Host localhost found: line 1 type ECDSA
/root/.ssh/known_hosts updated.
Original contents retained as /root/.ssh/known_hosts.old
Testing again
root#ubuntu:/# ssh localhost
The authenticity of host 'localhost (127.0.0.1)' can't be established.
ECDSA key fingerprint is 87:21:89:ac:cd:ce:bf:32:30:d6:d2:a2:dc:ff:6d:ad.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 14.04.5 LTS (GNU/Linux 4.4.0-31-generic x86_64)
* Documentation: https://help.ubuntu.com/
New release '16.04.3 LTS' available.
Run 'do-release-upgrade' to upgrade to it.
Last login: Wed Dec 20 07:13:15 2017 from localhost
Now, start Hadoop
root#ubuntu:/# cd $HADOOP_HOME
root#ubuntu:~/applications/hadoop/hadoop-2.9.0# sbin/start-all.sh
now always use the sudo -s root user login, before starting the hadoop cluster sbin/start-all or sbin/stop-all, otherwise you have to first mention yes and later provide the password for five times.