sshd
TLDR
Start SSH daemon
$ sshd
Test configuration$ sshd -t
Run in foreground$ sshd -D
Use alternate config$ sshd -f [/etc/ssh/sshd_config]
Debug mode$ sshd -d
Extended debug$ sshd -ddd
Specify port$ sshd -p [2222]
SYNOPSIS
sshd [-D] [-d] [-f config] [-p port] [options]
DESCRIPTION
sshd is the OpenSSH server daemon. It listens for SSH connections and authenticates users.
Configuration file controls behavior. Authentication methods, access controls, and features.
Debug mode helps troubleshoot connections. Multiple -d flags increase verbosity.
Test mode validates configuration. Catches errors before restart.
Foreground mode is useful for containers. Daemon doesn't detach from terminal.
PARAMETERS
-D
Foreground mode.-d
Debug mode.-t
Test configuration.-f FILE
Config file.-p PORT
Listen port.-e
Log to stderr.-q
Quiet mode.-4
IPv4 only.-6
IPv6 only.
CAVEATS
Requires root to bind port 22. Misconfiguration can lock you out. Test changes carefully.
HISTORY
sshd is part of OpenSSH, developed by the OpenBSD project starting in 1999. It replaced insecure protocols like telnet and rsh.
SEE ALSO
ssh(1), ssh-keygen(1), sshd_config(5)
