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Passphrase for ssh keypair ‘/home/ec2-user/.ssh/lab-3-key’ – AWS, ParallelCluster, FDS, Cloud9

I am attempting to run FDS (CFD code for fire simulation) on Cloud9 pcluster using the following tutorial:
https://fds-smv-on-pcluster.workshop.aws/oyo/setup/pcluster.html

Basically, you install ParallelCluster, create a new keypair, write a configuration file and then create the pcluster, then download FDS to the cluster and use Slurm to submit the job.

A few of the input commands in the tutorial are out of date, but I have gotten to the point where you connect to the PCluster with your created ssh lab key in order to download and install FDS software:

pcluster ssh --cluster-name pc-fsx -i ~/.ssh/lab-3-key

And I get asked for a passphrase:

Enter passphrase for key '/home/ec2-user/.ssh/lab-3-key': 

I do not know what this passphrase is. Is it created when I create my lab key? Is it from my AWS account or Cloud9 environment? I am relatively new to AWS and Python.
I tried AWS password, name of key, blank/no password, no luck.

FYI, the key is created as follows:


IFACE=$(curl --silent http://169.254.169.254/latest/meta-data/network/interfaces/macs/)
SUBNET_ID=$(curl --silent http://169.254.169.254/latest/meta-data/network/interfaces/macs/${IFACE}/subnet-id)
VPC_ID=$(curl --silent http://169.254.169.254/latest/meta-data/network/interfaces/macs/${IFACE}/vpc-id)
REGION=$(curl --silent http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/[a-z]$//')
AWS_REGION=$(curl --silent http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/[a-z]$//')

# generate a new key-pair
aws ec2 create-key-pair --key-name lab-3-your-key --query KeyMaterial --output text --region=${AWS_REGION} > ~/.ssh/lab-3-key
chmod 600 ~/.ssh/lab-3-key

I believe I did everything as the tutorial asked, as far as I could tell. Any help?