I was just sent a PEM key from a client as a means to access their Amazon EC2 instance. How do I convert this into something I could use with OpenSSH? 
How can I convert a PEM key into a RSA key pair?
ssh
You can extract a PEM public key from an OpenSSH private key using:openssl rsa -pubout -in .ssh/id_rsaBut OpenSSH has no tools to convert from or too PEM public keys (note: PEMprivate keys are OpenSSH's native format for protocol 2 keys)