LFCS: Linux Foundation Certified System AdministratorDemo

ssh-agent is the SSH authentication agent: it holds private keys in memory after they are unlocked once, and via environment variables (SSH_AUTH_SOCK, SSH_AGENT_PID) it is automatically located by the ssh client so that subsequent SSH logins to other hosts can be authenticated without re-entering the passphrase each time. This is distinct from ssh-add, which merely adds/loads a specific key into an already-running ssh-agent instance; sshd is the server-side daemon that accepts incoming SSH connections; and ssh-keygen is used to generate new key pairs, not to manage or preload them for authentication sessions.