SSH bad owner or permissions
OpenSSH refuses a config, private key, authorized_keys file, or home-directory path because another identity can modify it.
SSH certificate principal mismatch
A certificate is correctly signed but does not authorize the requested user or host principal.
SSH connection reset by peer
A TCP connection starts and is then closed abruptly by the server, firewall, proxy, or connection limiter.
SSH ControlPath too long
Connection multiplexing cannot create its Unix-domain control socket because the expanded path exceeds the platform limit or collides with another target.
SSH keeps disconnecting
An established session disappears after idle time or network changes, often because an intermediary expires state or the host stops responding.
Fix kex_exchange_identification
The SSH connection closes before or during initial key exchange, often because of pre-auth policy, rate limits, wrong routing, or incompatible early protocol behavior.
SSH key already in use
A service rejects a public key because that exact identity is already attached to another account, repository, or ownership boundary.
SSH remote port forwarding denied
Authentication succeeds, but the server refuses or cannot bind the requested -R listening endpoint.
SCP no such file or directory
The copy command resolves a source or destination on a different side, shell, home directory, or protocol than the user expects.
SSH agent not working
A key exists, but the current process cannot reach the intended agent or the agent does not hold the expected identity.