1. connect to host localhost port 22: Connection refused Stopping namenodes on [localhost] localhost: ssh: connect to host localhost port 22: Connection refused localhost: ssh: connect to host localhost port 22: Connection refused Stopping secondary namenodes [0.0.0.0] 0.0.0.0: ssh: connect to host 0.0.0.0 port 22: Connection refused Fix: thanooj@ubuntu:/$ sudo apt-get install openssh-server Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: ncurses-term openssh-sftp-server ssh-import-id Suggested packages: ssh-askpass rssh molly-guard monkeysphere The following NEW packages will be installed: ncurses-term openssh-server openssh-sftp-server ssh-import-id 0 upgraded, 4 newly installed, 0 to remove and 322 not upgraded. Need to get 636 kB of archives. After this operation, 5,145 kB of additional disk space will be used. Do you want to continue? [Y/n] Y Get:1 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 ncurses-term all 6.0+20160213-1ubuntu1 [249 kB] Get:2 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 openssh-sftp-server amd64 1:7.2p2-4ubuntu2.1 [38.8 kB] Get:3 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 openssh-server amd64 1:7.2p2-4ubuntu2.1 [338 kB] Get:4 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 ssh-import-id all 5.5-0ubuntu1 [10.2 kB] Fetched 636 kB in 4s (144 kB/s) Preconfiguring packages ... Selecting previously unselected package ncurses-term. (Reading database ... 204538 files and directories currently installed.) Preparing to unpack .../ncurses-term_6.0+20160213-1ubuntu1_all.deb ... Unpacking ncurses-term (6.0+20160213-1ubuntu1) ... Selecting previously unselected package openssh-sftp-server. Preparing to unpack .../openssh-sftp-server_1%3a7.2p2-4ubuntu2.1_amd64.deb ... Unpacking openssh-sftp-server (1:7.2p2-4ubuntu2.1) ... Selecting previously unselected package openssh-server. Preparing to unpack .../openssh-server_1%3a7.2p2-4ubuntu2.1_amd64.deb ... Unpacking openssh-server (1:7.2p2-4ubuntu2.1) ... Selecting previously unselected package ssh-import-id. Preparing to unpack .../ssh-import-id_5.5-0ubuntu1_all.deb ... Unpacking ssh-import-id (5.5-0ubuntu1) ... Processing triggers for man-db (2.7.5-1) ... Processing triggers for systemd (229-4ubuntu10) ... Processing triggers for ureadahead (0.100.0-19) ... Processing triggers for ufw (0.35-0ubuntu2) ... Setting up ncurses-term (6.0+20160213-1ubuntu1) ... Setting up openssh-sftp-server (1:7.2p2-4ubuntu2.1) ... Setting up openssh-server (1:7.2p2-4ubuntu2.1) ... Creating SSH2 RSA key; this may take some time ... 2048 SHA256:Z0Ua5wQ/Ys2VkMXY6EHO3piE8wR2eDVWKfJ8QjmBf+s root@ubuntu (RSA) Creating SSH2 DSA key; this may take some time ... 1024 SHA256:QVf/9MFGymmWAt6GPeRdQPtfL0XJiq9jzFtPyax5iZo root@ubuntu (DSA) Creating SSH2 ECDSA key; this may take some time ... 256 SHA256:FO49jCgn6J1yciS0OxC3KnRgzLGIty0mlBXXEcIYerA root@ubuntu (ECDSA) Creating SSH2 ED25519 key; this may take some time ... 256 SHA256:NRTS+9qFjP1GdOvAFN1iXfQslb5scIGLJg52foOc+Nw root@ubuntu (ED25519) Setting up ssh-import-id (5.5-0ubuntu1) ... Processing triggers for systemd (229-4ubuntu10) ... Processing triggers for ureadahead (0.100.0-19) ... Processing triggers for ufw (0.35-0ubuntu2) ... thanooj@ubuntu:/$ thanooj@ubuntu:/$ sudo /etc/init.d/ssh restart [ ok ] Restarting ssh (via systemctl): ssh.service. thanooj@ubuntu:/$ thanooj@ubuntu:/$ netstat -tulpn | grep 22 (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN - tcp6 0 0 :::22 :::* LISTEN - thanooj@ubuntu:/$ thanooj@ubuntu:/$ start-dfs.sh 16/11/12 12:05:20 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable Starting namenodes on [localhost] The authenticity of host 'localhost (127.0.0.1)' can't be established. ECDSA key fingerprint is SHA256:FO49jCgn6J1yciS0OxC3KnRgzLGIty0mlBXXEcIYerA. Are you sure you want to continue connecting (yes/no)? yes localhost: Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts. thanooj@localhost's password: localhost: starting namenode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-namenode-ubuntu.out thanooj@localhost's password: localhost: starting datanode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-datanode-ubuntu.out Starting secondary namenodes [0.0.0.0] The authenticity of host '0.0.0.0 (0.0.0.0)' can't be established. ECDSA key fingerprint is SHA256:FO49jCgn6J1yciS0OxC3KnRgzLGIty0mlBXXEcIYerA. Are you sure you want to continue connecting (yes/no)? yes 0.0.0.0: Warning: Permanently added '0.0.0.0' (ECDSA) to the list of known hosts. thanooj@0.0.0.0's password: 0.0.0.0: starting secondarynamenode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-secondarynamenode-ubuntu.out 16/11/12 12:06:34 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable thanooj@ubuntu:/$ thanooj@ubuntu:/$ jps 11254 SecondaryNameNode 11078 DataNode 10936 NameNode 11418 Jps thanooj@ubuntu:/$ start-yarn.sh starting yarn daemons starting resourcemanager, logging to /home/thanooj/hadoop-2.7.3/logs/yarn-thanooj-resourcemanager-ubuntu.out thanooj@localhost's password: localhost: starting nodemanager, logging to /home/thanooj/hadoop-2.7.3/logs/yarn-thanooj-nodemanager-ubuntu.out thanooj@ubuntu:/$ jps 11254 SecondaryNameNode 11078 DataNode 10936 NameNode 11690 Jps 11596 NodeManager 11471 ResourceManager thanooj@ubuntu:/$ Note: An alternative to start hadoop without ssh is by using : hadoop-daemon.sh start [daemon-name] 2. thanooj@ubuntu:/$ start-dfs.sh 16/11/12 12:23:33 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable Fix: thanooj@ubuntu:/$ gedit ~/.bashrc export HADOOP_COMMON_LIB_NATIVE_DIR=$HADOOP_HOME/lib/native export HADOOP_OPTS="-Djava.library.path=$HADOOP_HOME/lib/native" save it and close gedit, then, source thanooj@ubuntu:/$ source ~/.bashrc 3. Passwordless ssh login thanooj@ubuntu:/$ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/home/thanooj/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/thanooj/.ssh/id_rsa. Your public key has been saved in /home/thanooj/.ssh/id_rsa.pub. The key fingerprint is: SHA256:2kIaoMf+FvOeCUQqOYwdhwrZ13cY9vMRKiEeG+XTIUg thanooj@ubuntu The key's randomart image is: +---[RSA 2048]----+ | .Eo* . . | | o . o.B B o . | |o = + + * * . | |+* B . + o . | |B.= o . S . | | = .o+ o | | . o+o . | | ....+ | | ...+ | +----[SHA256]-----+ thanooj@ubuntu:/$ ssh-copy-id thanooj@127.0.0.1 The authenticity of host '127.0.0.1 (127.0.0.1)' can't be established. ECDSA key fingerprint is SHA256:FO49jCgn6J1yciS0OxC3KnRgzLGIty0mlBXXEcIYerA. Are you sure you want to continue connecting (yes/no)? yes /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys thanooj@127.0.0.1's password: Number of key(s) added: 1 Now try logging into the machine, with: "ssh 'thanooj@127.0.0.1'" and check to make sure that only the key(s) you wanted were added. thanooj@ubuntu:/$ ssh thanooj@127.0.0.1 thanooj@127.0.0.1's password: Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-45-generic x86_64) * Documentation: https://help.ubuntu.com/ 319 packages can be updated. 30 updates are security updates. thanooj@ubuntu:~$ ssh 'thanooj@localhost' thanooj@localhost's password: Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-45-generic x86_64) * Documentation: https://help.ubuntu.com/ 319 packages can be updated. 30 updates are security updates. Last login: Sat Nov 12 12:38:51 2016 from 127.0.0.1 thanooj@ubuntu:~$ ssh-copy-id thanooj@0.0.0.0 /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/thanooj/.ssh/id_rsa.pub" /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys thanooj@0.0.0.0's password: Number of key(s) added: 1 Now try logging into the machine, with: "ssh 'thanooj@0.0.0.0'" and check to make sure that only the key(s) you wanted were added. thanooj@ubuntu:~$ ssh 'thanooj@0.0.0.0' thanooj@0.0.0.0's password: Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-45-generic x86_64) * Documentation: https://help.ubuntu.com/ 319 packages can be updated. 30 updates are security updates. Last login: Sat Nov 12 12:45:57 2016 from 127.0.0.1 thanooj@ubuntu:~$ thanooj@ubuntu:~$ start-all.sh This script is Deprecated. Instead use start-dfs.sh and start-yarn.sh Starting namenodes on [localhost] thanooj@localhost's password: localhost: starting namenode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-namenode-ubuntu.out thanooj@localhost's password: localhost: starting datanode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-datanode-ubuntu.out Starting secondary namenodes [0.0.0.0] thanooj@0.0.0.0's password: 0.0.0.0: starting secondarynamenode, logging to /home/thanooj/hadoop-2.7.3/logs/hadoop-thanooj-secondarynamenode-ubuntu.out starting yarn daemons starting resourcemanager, logging to /home/thanooj/hadoop-2.7.3/logs/yarn-thanooj-resourcemanager-ubuntu.out thanooj@localhost's password: localhost: starting nodemanager, logging to /home/thanooj/hadoop-2.7.3/logs/yarn-thanooj-nodemanager-ubuntu.out thanooj@ubuntu:~$ jps 17107 DataNode 17446 ResourceManager 17879 Jps 17756 NodeManager 17293 SecondaryNameNode 16957 NameNode thanooj@ubuntu:~$