I need SSH access to an Amazon EC2 instance running Ubuntu 10.4. All I have is the Amazon username and password. Any ideas?
Not logging in as the correct user for you OS Distro could be the issue. For certain new AMI, the username may not be "ubuntu", but "ec2-user". For Amazon Linux, for instance I believe the user is "ec2-user". Eric Hammond gives examples here: http://alestic.com/2014/01/ec2-ssh-username
My suggestion, try:
ssh -i /path/to/file.pem ec2-user@ec2...
ssh -i /path/to/file.pem ubuntu@ec2...
ssh -i /path/to/file.pem root@ec2...
If you have the wrong AMI, you might just want to restart the machine altogether so you have uniformity amongst your clusters. If this is your problem, you'll probably want the same OS Distro's at least for your linux boxes.