5.2. Set Up Password-less SSH

To have Ambari Server automatically install Ambari Agents in all your cluster hosts, you must set up password-less SSH connections between the main installation (Ambari Server) host and all other machines. The Ambari Server host acts as the client and uses the key-pair to access the other hosts in the cluster to install the Ambari Agent.

	Note
	You can choose to install the Agents on each cluster host manually. In this case you do not need to setup SSH. See Appendix: Installing Ambari Agents Manually for more information.

Generate public and private SSH keys on the Ambari Server host
```
ssh-keygen
```
Copy the SSH Public Key (id_rsa.pub) to the root account on your target hosts.
```
.ssh/id_rsa
.ssh/id_rsa.pub
```
Add the SSH Public Key to the authorized_keys file on your target hosts.
```
cat id_rsa.pub >> authorized_keys
```
Depending on your version of SSH, you may need to set permissions on the .ssh directory (to 700) and the authorized_keys file in that directory (to 600) on the target hosts.
```
chmod 700 ~/.ssh
chmod 600 ~/.ssh /authorized_keys
```
From the Ambari Server, make sure you can connect to each host in the cluster using SSH.
```
ssh root@{remote.target.host}
```
You may see this warning. This happens on your first connection and is normal.
```
Are you sure you want to continue connecting (yes/no)?
```

Retain a copy of the SSH Private Key on the machine from which you will run the web-based Ambari Install Wizard.

	Note
	It is possible to use a non-root SSH account, if that account can execute `sudo` without entering a password.

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