If you use a newer SSH key generated with the ED25519 algorithm instead of RSA (see Create a new SSH key pair), the deployment with Capistrano may fail with the following message:
The deploy has failed with an error: unsupported key type `ssh-ed25519' net-ssh requires the following gems for ed25519 support: * ed25519 (>= 1.2, < 2.0) * bcrypt_pbkdf (>= 1.0, < 2.0) See https://github.com/net-ssh/net-ssh/issues/565 for more information Gem::LoadError : "ed25519 is not part of the bundle. Add it to your Gemfile."
As described in the error message, the
bcrypt_pbkdf gems must be added to the Gemfile to solve the problem. Now, the deployment should work faultlessly again.