Sorry if this is an obvious question. My Linux/Unix system is missing man pages. Does ssh-keygen default to rsa when given no options? Does ssh-keygen default to rsa on all Linux/Unix systems when given no options? I did notice in my `$HOME/.ssh` directory it created a `id_rsa.pub`file.
Yes, rsa is supported since a long time, by most openssh versions.
Recent openssh might default to Ed25519, so run
ssh-keygen -t rsa
to ensure rsa for the best cross-platform compatibility.
Unix might have a vendor-ssh that is based on an old openssh version.
BTW you can type "man ssh-keygen linux" in your browser's search field...
Thank you.