Lambda — Verify

Progress checklist

• Lambda function invoked with exit code 200
• /mnt/s3files listing returned in the response body
• CloudWatch logs confirm the function ran without errors

Overview

Invoke the function and read the JSON response to confirm the file system is mounted and accessible at /mnt/s3files.

1. Confirm base exports. Required

   export AWS_REGION=ap-southeast-6
   export FUNCTION_NAME=s3files-demo

2. Invoke the function. Required

   aws lambda invoke \
     --function-name "$FUNCTION_NAME" \
     --region "$AWS_REGION" \
     --payload '{}' \
     /tmp/lambda-response.json \
   && cat /tmp/lambda-response.json

   Expected response:

   {"statusCode": 200, "body": "[]"}

   An empty list [] is correct for a newly created file system. The function successfully listed /mnt/s3files.

   Note

   If the first invocation returns a timeout or mount error, the mount target may still be establishing the NFS connection. Wait 60 seconds and retry. Cold-start Lambda invocations with VPC + file system configs can take 10–30 seconds on the first call.

   Tip

   If the response body contains [Errno 13] Permission denied, the access point POSIX UID/GID (1000) does not match the file system root permissions. Confirm that the access point was created with OwnerUid=1000,OwnerGid=1000,Permissions=755 in Access Point.

3. Write an object via S3 and invoke again. Required

   Write a file directly to the S3 bucket at the path the access point exposes (/lambda/):

   export BUCKET=my-s3-files-bucket   # ← replace with your real bucket name
   
   aws s3 cp /dev/stdin \
     "s3://${BUCKET}/lambda/hello.txt" \
     --content-type text/plain \
     --region "$AWS_REGION" <<< "hello from lambda walkthrough"

   Invoke the function again:

   aws lambda invoke \
     --function-name "$FUNCTION_NAME" \
     --region "$AWS_REGION" \
     --payload '{}' \
     /tmp/lambda-response.json \
   && cat /tmp/lambda-response.json

   The response body should now list ['hello.txt'].

4. Check CloudWatch Logs. Required

   aws logs tail \
     "/aws/lambda/${FUNCTION_NAME}" \
     --since 5m \
     --region "$AWS_REGION"

   Look for a log line like Contents of /mnt/s3files: ['hello.txt'].

Next step

When you are finished, run Teardown to remove the file system config, delete access points, and clean up all resources.