我正试图在amazonec2集群中运行graphlab，但是我面临一些关于设置的问题。我知道这是一个基本的问题，但我不能弄清楚这个问题。1） 当我在ubuntu中运行命令/gl-ec2-i~/.ssh/graphlab.pem-k graphlabkey-s1 launchtest for graphlab时，它给了我一个错误

Launching instances...
ERROR:boto:400 Bad Request
ERROR:boto:<?xml version="1.0" encoding="UTF-8"?>
<Response><Errors><Error><Code>InvalidKeyPair.NotFound</Code><Message>The key pair 'Prashant-Raghav' does not exist</Message></Error></Errors><RequestID>366d452a-921d-4feb-a9d1-50bf8ccc2f55</RequestID></Response>
Traceback (most recent call last):
  File "./gl_ec2.py", line 750, in <module>
    main()
  File "./gl_ec2.py", line 532, in main
    conn, opts, cluster_name)
  File "./gl_ec2.py", line 282, in launch_cluster
    block_device_map = block_map)
  File "/home/hduser/graphlab/scripts/ec2/third_party/boto-2.4.1.zip/boto-2.4.1/boto/ec2/image.py", line 255, in run
  File "/home/hduser/graphlab/scripts/ec2/third_party/boto-2.4.1.zip/boto-2.4.1/boto/ec2/connection.py", line 678, in run_instances
  File "/home/hduser/graphlab/scripts/ec2/third_party/boto-2.4.1.zip/boto-2.4.1/boto/connection.py", line 925, in get_object
boto.exception.EC2ResponseError: EC2ResponseError: 400 Bad Request
<?xml version="1.0" encoding="UTF-8"?>
<Response><Errors><Error><Code>InvalidKeyPair.NotFound</Code><Message>The key pair 'Prashant-Raghav' does not exist</Message></Error></Errors><RequestID>366d452a-921d-4feb-a9d1-50bf8ccc2f55</RequestID></Response>

1） 我无法在ssh中找到生成的.pem文件。2） 我已经创建了一个ppk文件，我可以用它来运行graphlab吗3）eern.ppk和.pem之间有什么区别4）当我创建密钥对时，ec2中的密钥对存储在哪里？它存储在windows中，但是在linux中有没有什么方法可以让我指定路径..请帮助
谢谢