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i am trying to login to my amazon instance using putty. I had logged in a few hours back, but now when i am trying to log back in, it says authentication using the key has failed. Anyway i can fix this?

Now putty is not able to connect to the server. I tried with the public dns and elastic ip. neither one was able to connect. But the server is still running.

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Did you change something? – ceejayoz Sep 18 '11 at 16:38
Have the permissions on your key changed? Did you modify the EC2 firewall? – Trent Scott Sep 19 '11 at 2:53

First, I would try manually rebooting the instance from the AWS Management console. If that doesn't do it, you'll need to shut down the instance (but save the EBS volume first by taking a snapshot if you have it set to delete on instance termination). You can then start a new instance and attach the volume to it recover your data.

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tried the manual reboot, stop start. Dint work. Not sure of the steps of attaching a volume on boot to an instance. – Nithin Sep 20 '11 at 5:50

I wrote this article to help start tracking down these types of problems. It also has useful tips on what information you should provide when you ask for help:

Solving: "I can't connect to my server on Amazon EC2"

I wrote this article to help explain how to look at and fix files on the root disk of an instance when you can't connect to it:

Fixing Files on the Root EBS Volume of an EC2 Instance

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Thanks, will read through it. – Nithin Sep 20 '11 at 5:50

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