What does the error missing begin marker mean

Question

When trying to ssh to a server hosting some code, I get

debug1: Trying private key: /home/ubuntu/.ssh/build_key.rsa
debug1: key_parse_private2: missing begin marker

What does "missing begin marker" mean?

Answer 1

It is not an error. It is just harmless debug information that is printed during the parsing of different key types.