8.6. SSH Configuration

In order to run presto-admin, the node that is running presto-admin must be able to connect to all of the nodes running Presto via SSH. presto-admin makes the SSH connection with the username and port specified in ~/.prestoadmin/config.json. Even if you have a single-node installation, ssh username@localhost needs to work properly.

There are two ways to configure SSH: with keys so that you can use passwordless SSH, or with passwords. If your cluster already has passwordless SSH configured for the username user, you can skip this step if the username is root, otherwise the root public key (id_rsa.pub) needs to be appended to the non-root username’s authorized_keys file. If you are intending to use presto-admin with passwords, take a look at the documentation below, because there are several ways to specify the password.

Using presto-admin with passwordless SSH

In order to set up passwordless SSH, you must first login as username on the presto-admin node and generate keys with no passphrase on the node running presto-admin:

ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa

While logged in as username, copy the public key to all of the coordinator and worker nodes:

ssh <username>@<ip> "mkdir -p ~/.ssh && chmod 700 ~/.ssh"
scp ~/.ssh/id_rsa.pub <username>@<ip>:~/.ssh/id_rsa.pub

Log into all of those nodes and append the public key to the authorized key file:

ssh <username>@<ip> "cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

For non-root username, log into all of those nodes and append the root user public key to the username authorized key file, provided the passwordless ssh has been setup for root user.:

ssh <username>@<ip> "sudo cat /root/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

Once you have passwordless SSH set up, you can just run presto-admin commands as they appear in the documentation. If your private key is not in ~/.ssh, it is possible to specify one or several private keys using the -i CLI option:

./presto-admin <command> -i <path_to_private_key> -i <path_to_second_private_key>

Please also note that it is not common for servers to allow passwordless SSH for root because of security concerns, so it is preferable for the SSH user not to be root.

Using presto-admin with SSH passwords

If you do not want to set up passwordless SSH on your cluster, it is possible to use presto-admin with SSH passwords. However, you will need to add a password argument to the presto-admin commands as they appear in the documentation. There are several options. To specify a password on the CLI in plaintext:

./presto-admin <command> -p <password>

However, from a security perspective, it is preferable not to type your password in plaintext. Thus, it is also possible to add an interactive password prompt, which prompts you for the initial value of your password before running any commands:

./presto-admin <command> -I
Initial value for env.password: <type your password here>

If you do not specify a password, the command will fail with a parallel execution failure, since, by default, presto-admin runs in parallel and cannot prompt for a password while running in parallel. If you specify the --serial option for presto-admin, presto-admin will prompt you for a password if it cannot connect.

Please note that the SSH password for the user specified in ~/.prestoadmin/config.json must match the sudo password for that user.