SSH Connection without password is not working

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.