2.3. Preparing the Cluster Nodes for Management


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2.3. Preparing the Cluster Nodes for Management

The Enterprise Manager comes complete with all of the software needed to run VoltDB. When you start a VoltDB cluster using the management console, all of the necessary files including the VoltDB software and the database catalog and deployment files are copied to all nodes automatically. So you do not need to manually install any VoltDB software on the cluster nodes themselves

However, you must prepare the cluster nodes so that the management console can communicate with them. The Enterprise Manager uses SSH and SFTP to perform many functions, including copying files to the cluster nodes and starting the database process. (The Manager also uses native VoltDB system procedures to interact with the database once it is up and running.)

Before you start the Enterprise Manager, you must make sure the server can reach the cluster nodes using SSH and that SFTP is enabled. SFTP is usually enabled by default. However, if you are not sure, check the SSH configuration file (in most cases /etc/ssh/sshd_config) and make sure the following line is present and not commented out:

Subsystem sftp /usr/lib/openssh/sftp-server

SSH should be set up with public keys for enhanced security and password-less access. If you are using SSH with public keys, you need to create an SSH key file on the server where the Manager will run. You then copy the appropriate key files to an account on each of the cluster nodes.

Once you believe you have SSH set up properly, it is a good idea to test the configuration before starting the Enterprise Manager. From the command line on the server that will run the Enterprise Manager process, use the ssh command to connect to each of the database servers that will be used. If the connection succeeds, the configuration is correct. If the connection requests a password before continuing (or generates a permission error), the configuration is not correct. In the following example, the user tests the connection to three servers: first using the default account on Athens, then using the account romulus on Rome, and finally the account napolean and the keyfile .ssh/mykey.key on Paris:

$ ssh athens
$ ssh romulus@rome
$ ssh napolean@paris -i .ssh/mykey.key

If you are unfamiliar with SSH, there are instructions for setting it up available on the web. For example http://www.debian-administration.org/articles/152.