Converting openssh private key to PEM format

Newer version of the openssh will use their own format to store a private key:

-----BEGIN OPENSSH PRIVATE KEY-----
BASE64KEYTEXT
-----END OPENSSH PRIVATE KEY-----

The traditional format of the key can sometimes be useful (or even required - for example guacamole will not be able to use the OPENSSH key format).

To convert the key use ssh-keygen. The command will overwrite the private key file, so if the original key should be preserved make sure to create a backup:

1ssh-keygen -p -m PEM -f ~/.ssh/id_rsa_test

-----BEGIN RSA PRIVATE KEY-----
BASE64KEYTEXT
-----END RSA PRIVATE KEY-----