HyperPod SSM Access

Prerequisites

• aws CLI v2, authenticated for the target account/Region.
• session-manager-plugin — installed alongside the AWS CLI.
• jq — the scripts build JSON payloads with it.
• unbuffer (from the expect package) — wraps aws ssm start-session with a PTY so the session-manager-plugin flushes stdout instead of racing to close. Without it, calls intermittently return empty output with Cannot perform start session: EOF even when the command ran. Install with sudo yum install expect, sudo apt install expect, or brew install expect. ssm-exec.sh detects and uses it automatically; falls back with a warning if missing.

SSM Target Format

Target: sagemaker-cluster:<CLUSTER_ID>_<GROUP_NAME>-<INSTANCE_ID>

• CLUSTER_ID: Last segment of cluster ARN (NOT the cluster name). Extract via get-cluster-info.sh.
• GROUP_NAME: Instance group name — retrieve via list-nodes.sh.
• INSTANCE_ID: EC2 instance ID (e.g., i-0123456789abcdef0)

Scripts

Three scripts under scripts/. Resolve cluster info and nodes once, then execute per node.

get-cluster-info.sh — Resolve cluster name → ID (call once)

scripts/get-cluster-info.sh CLUSTER_NAME [--region REGION]
# Output: {"cluster_id":"...","cluster_arn":"...","cluster_name":"...","region":"..."}

list-nodes.sh — List all nodes with pagination (call once)

scripts/list-nodes.sh CLUSTER_NAME [--region REGION] [--instance-group GROUP] [--instance-id ID]
# Output: JSON array of ClusterNodeSummaries (InstanceId, InstanceGroupName, InstanceStatus, etc.)

list-cluster-nodes paginates at 100 nodes. This script handles pagination automatically.

ssm-exec.sh — Execute command on a node (call per node)

# Execute — with pre-built target
scripts/ssm-exec.sh --target "sagemaker-cluster:CLUSTERID_GROUP-INSTANCEID" 'command' [--region REGION]

# Execute — with parts
scripts/ssm-exec.sh --cluster-id ID --group GROUP --instance-id INSTANCE_ID 'command' [--region REGION]

# Upload
scripts/ssm-exec.sh --target TARGET --upload LOCAL_PATH REMOTE_PATH [--region REGION]

# Read remote file
scripts/ssm-exec.sh --target TARGET --read REMOTE_PATH [--region REGION]

Running Commands Across Many Nodes

SSM start-session rate limit: 3 TPS per account. Plan batch size and delay accordingly.

aws ssm send-command does NOT support sagemaker-cluster: targets — only start-session works.

Manual SSM Commands

When the scripts aren't suitable, use aws ssm start-session directly with AWS-StartNonInteractiveCommand. Wrap every invocation in unbuffer — without it, stdout is intermittently empty (see Prerequisites).

cat > /tmp/cmd.json << 'EOF'
{"command": ["bash -c 'echo hello && whoami'"]}
EOF

unbuffer aws ssm start-session \
  --target sagemaker-cluster:{CLUSTER_ID}_{GROUP_NAME}-{INSTANCE_ID} \
  --region REGION \
  --document-name AWS-StartNonInteractiveCommand \
  --parameters file:///tmp/cmd.json

• Always use a JSON file for --parameters — inline parameters break with special characters.
• The document's command parameter is argv, not shell input. Wrap multi-statement scripts in bash -c '...' so pipes, semicolons, and redirects evaluate.

Common Diagnostic Commands

Key Details

• Default SSM non-interactive user is root.
• SSM rate limit: 3 TPS per account.
• For interactive sessions (rare), omit --document-name to get a shell.
• Interactive commands (vim, top) are not supported via AWS-StartNonInteractiveCommand.
• Large outputs may be truncated by SSM.
• For troubleshooting common errors, see references/troubleshooting.md.