Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
SSHD(8)			  BSD System Manager's Manual		       SSHD(8)

NAME
     sshd -- OpenSSH SSH daemon

SYNOPSIS
     sshd [-46DdeiqTt] [-C connection_spec] [-c	host_certificate_file]
	  [-E log_file]	[-f config_file] [-g login_grace_time]
	  [-h host_key_file] [-o option] [-p port] [-u len]

DESCRIPTION
     sshd (OpenSSH Daemon) is the daemon program for ssh(1).  Together these
     programs replace rlogin and rsh, and provide secure encrypted communica-
     tions between two untrusted hosts over an insecure	network.

     sshd listens for connections from clients.	 It is normally	started	at
     boot from /etc/rc.d/sshd.	It forks a new daemon for each incoming	con-
     nection.  The forked daemons handle key exchange, encryption, authentica-
     tion, command execution, and data exchange.

     sshd can be configured using command-line options or a configuration file
     (by default sshd_config(5)); command-line options override	values speci-
     fied in the configuration file.  sshd rereads its configuration file when
     it	receives a hangup signal, SIGHUP, by executing itself with the name
     and options it was	started	with, e.g. /usr/sbin/sshd.

     The options are as	follows:

     -4	     Forces sshd to use	IPv4 addresses only.

     -6	     Forces sshd to use	IPv6 addresses only.

     -C	connection_spec
	     Specify the connection parameters to use for the -T extended test
	     mode.  If provided, any Match directives in the configuration
	     file that would apply are applied before the configuration	is
	     written to	standard output.  The connection parameters are	sup-
	     plied as keyword=value pairs and may be supplied in any order,
	     either with multiple -C options or	as a comma-separated list.
	     The keywords are "addr," "user", "host", "laddr", "lport",	and
	     "rdomain" and correspond to source	address, user, resolved	source
	     host name,	local address, local port number and routing domain
	     respectively.

     -c	host_certificate_file
	     Specifies a path to a certificate file to identify	sshd during
	     key exchange.  The	certificate file must match a host key file
	     specified using the -h option or the HostKey configuration	direc-
	     tive.

     -D	     When this option is specified, sshd will not detach and does not
	     become a daemon.  This allows easy	monitoring of sshd.

     -d	     Debug mode.  The server sends verbose debug output	to standard
	     error, and	does not put itself in the background.	The server
	     also will not fork	and will only process one connection.  This
	     option is only intended for debugging for the server.  Multiple
	     -d	options	increase the debugging level.  Maximum is 3.

     -E	log_file
	     Append debug logs to log_file instead of the system log.

     -e	     Write debug logs to standard error	instead	of the system log.

     -f	config_file
	     Specifies the name	of the configuration file.  The	default	is
	     /etc/ssh/sshd_config.  sshd refuses to start if there is no con-
	     figuration	file.

     -g	login_grace_time
	     Gives the grace time for clients to authenticate themselves (de-
	     fault 120 seconds).  If the client	fails to authenticate the user
	     within this many seconds, the server disconnects and exits.  A
	     value of zero indicates no	limit.

     -h	host_key_file
	     Specifies a file from which a host	key is read.  This option must
	     be	given if sshd is not run as root (as the normal	host key files
	     are normally not readable by anyone but root).  The default is
	     /etc/ssh/ssh_host_ecdsa_key, /etc/ssh/ssh_host_ed25519_key	and
	     /etc/ssh/ssh_host_rsa_key.	 It is possible	to have	multiple host
	     key files for the different host key algorithms.

     -i	     Specifies that sshd is being run from inetd(8).

     -o	option
	     Can be used to give options in the	format used in the configura-
	     tion file.	 This is useful	for specifying options for which there
	     is	no separate command-line flag.	For full details of the	op-
	     tions, and	their values, see sshd_config(5).

     -p	port
	     Specifies the port	on which the server listens for	connections
	     (default 22).  Multiple port options are permitted.  Ports	speci-
	     fied in the configuration file with the Port option are ignored
	     when a command-line port is specified.  Ports specified using the
	     ListenAddress option override command-line	ports.

     -q	     Quiet mode.  Nothing is sent to the system	log.  Normally the be-
	     ginning, authentication, and termination of each connection is
	     logged.

     -T	     Extended test mode.  Check	the validity of	the configuration
	     file, output the effective	configuration to stdout	and then exit.
	     Optionally, Match rules may be applied by specifying the connec-
	     tion parameters using one or more -C options.

     -t	     Test mode.	 Only check the	validity of the	configuration file and
	     sanity of the keys.  This is useful for updating sshd reliably as
	     configuration options may change.

     -u	len  This option is used to specify the	size of	the field in the utmp
	     structure that holds the remote host name.	 If the	resolved host
	     name is longer than len, the dotted decimal value will be used
	     instead.  This allows hosts with very long	host names that	over-
	     flow this field to	still be uniquely identified.  Specifying -u0
	     indicates that only dotted	decimal	addresses should be put	into
	     the utmp file.  -u0 may also be used to prevent sshd from making
	     DNS requests unless the authentication mechanism or configuration
	     requires it.  Authentication mechanisms that may require DNS in-
	     clude HostbasedAuthentication and using a from="pattern-list" op-
	     tion in a key file.  Configuration	options	that require DNS in-
	     clude using a USER@HOST pattern in	AllowUsers or DenyUsers.

AUTHENTICATION
     The OpenSSH SSH daemon supports SSH protocol 2 only.  Each	host has a
     host-specific key,	used to	identify the host.  Whenever a client con-
     nects, the	daemon responds	with its public	host key.  The client compares
     the host key against its own database to verify that it has not changed.
     Forward security is provided through a Diffie-Hellman key agreement.
     This key agreement	results	in a shared session key.  The rest of the ses-
     sion is encrypted using a symmetric cipher, currently 128-bit AES,	Blow-
     fish, 3DES, CAST128, Arcfour, 192-bit AES,	or 256-bit AES.	 The client
     selects the encryption algorithm to use from those	offered	by the server.
     Additionally, session integrity is	provided through a cryptographic mes-
     sage authentication code (hmac-md5, hmac-sha1, umac-64, umac-128, hmac-
     sha2-256 or hmac-sha2-512).

     Finally, the server and the client	enter an authentication	dialog.	 The
     client tries to authenticate itself using host-based authentication, pub-
     lic key authentication, challenge-response	authentication,	or password
     authentication.

     Regardless	of the authentication type, the	account	is checked to ensure
     that it is	accessible.  An	account	is not accessible if it	is locked,
     listed in DenyUsers or its	group is listed	in DenyGroups .	 The defini-
     tion of a locked account is system	dependent. Some	platforms have their
     own account database (eg AIX) and some modify the passwd field ( `*LK*'
     on	Solaris	and UnixWare, `*' on HP-UX, containing `Nologin' on Tru64, a
     leading `*LOCKED*'	on FreeBSD and a leading `!' on	most Linuxes).	If
     there is a	requirement to disable password	authentication for the account
     while allowing still public-key, then the passwd field should be set to
     something other than these	values (eg `NP'	or `*NP*' ).

     If	the client successfully	authenticates itself, a	dialog for preparing
     the session is entered.  At this time the client may request things like
     allocating	a pseudo-tty, forwarding X11 connections, forwarding TCP con-
     nections, or forwarding the authentication	agent connection over the se-
     cure channel.

     After this, the client either requests a shell or execution of a command.
     The sides then enter session mode.	 In this mode, either side may send
     data at any time, and such	data is	forwarded to/from the shell or command
     on	the server side, and the user terminal in the client side.

     When the user program terminates and all forwarded	X11 and	other connec-
     tions have	been closed, the server	sends command exit status to the
     client, and both sides exit.

LOGIN PROCESS
     When a user successfully logs in, sshd does the following:

	   1.	If the login is	on a tty, and no command has been specified,
		prints last login time and /etc/motd (unless prevented in the
		configuration file or by ~/.hushlogin; see the FILES section).

	   2.	If the login is	on a tty, records login	time.

	   3.	Checks /etc/nologin and	/var/run/nologin; if one exists, it
		prints the contents and	quits (unless root).

	   4.	Changes	to run with normal user	privileges.

	   5.	Sets up	basic environment.

	   6.	Reads the file ~/.ssh/environment, if it exists, and users are
		allowed	to change their	environment.  See the
		PermitUserEnvironment option in	sshd_config(5).

	   7.	Changes	to user's home directory.

	   8.	If ~/.ssh/rc exists and	the sshd_config(5) PermitUserRC	option
		is set,	runs it; else if /etc/ssh/sshrc	exists,	runs it; oth-
		erwise runs xauth(1).  The "rc"	files are given	the X11	au-
		thentication protocol and cookie in standard input.  See
		SSHRC, below.

	   9.	Runs user's shell or command.  All commands are	run under the
		user's login shell as specified	in the system password data-
		base.

SSHRC
     If	the file ~/.ssh/rc exists, sh(1) runs it after reading the environment
     files but before starting the user's shell	or command.  It	must not pro-
     duce any output on	stdout;	stderr must be used instead.  If X11 forward-
     ing is in use, it will receive the	"proto cookie" pair in its standard
     input (and	DISPLAY	in its environment).  The script must call xauth(1)
     because sshd will not run xauth automatically to add X11 cookies.

     The primary purpose of this file is to run	any initialization routines
     which may be needed before	the user's home	directory becomes accessible;
     AFS is a particular example of such an environment.

     This file will probably contain some initialization code followed by
     something similar to:

	if read	proto cookie &&	[ -n "$DISPLAY"	]; then
		if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
			# X11UseLocalhost=yes
			echo add unix:`echo $DISPLAY |
			    cut	-c11-` $proto $cookie
		else
			# X11UseLocalhost=no
			echo add $DISPLAY $proto $cookie
		fi | xauth -q -
	fi

     If	this file does not exist, /etc/ssh/sshrc is run, and if	that does not
     exist either, xauth is used to add	the cookie.

AUTHORIZED_KEYS	FILE FORMAT
     AuthorizedKeysFile	specifies the files containing public keys for public
     key authentication; if this option	is not specified, the default is
     ~/.ssh/authorized_keys and	~/.ssh/authorized_keys2.  Each line of the
     file contains one key (empty lines	and lines starting with	a `#' are ig-
     nored as comments).  Public keys consist of the following space-separated
     fields: options, keytype, base64-encoded key, comment.  The options field
     is	optional.  The keytype is "ecdsa-sha2-nistp256",
     "ecdsa-sha2-nistp384", "ecdsa-sha2-nistp521", "ssh-ed25519", "ssh-dss" or
     "ssh-rsa";	the comment field is not used for anything (but	may be conve-
     nient for the user	to identify the	key).

     Note that lines in	this file can be several hundred bytes long (because
     of	the size of the	public key encoding) up	to a limit of 8	kilobytes,
     which permits DSA keys up to 8 kilobits and RSA keys up to	16 kilobits.
     You don't want to type them in; instead, copy the id_dsa.pub,
     id_ecdsa.pub, id_ed25519.pub, or the id_rsa.pub file and edit it.

     sshd enforces a minimum RSA key modulus size of 1024 bits.

     The options (if present) consist of comma-separated option	specifica-
     tions.  No	spaces are permitted, except within double quotes.  The	fol-
     lowing option specifications are supported	(note that option keywords are
     case-insensitive):

     agent-forwarding
	     Enable authentication agent forwarding previously disabled	by the
	     restrict option.

     cert-authority
	     Specifies that the	listed key is a	certification authority	(CA)
	     that is trusted to	validate signed	certificates for user authen-
	     tication.

	     Certificates may encode access restrictions similar to these key
	     options.  If both certificate restrictions	and key	options	are
	     present, the most restrictive union of the	two is applied.

     command="command"
	     Specifies that the	command	is executed whenever this key is used
	     for authentication.  The command supplied by the user (if any) is
	     ignored.  The command is run on a pty if the client requests a
	     pty; otherwise it is run without a	tty.  If an 8-bit clean	chan-
	     nel is required, one must not request a pty or should specify
	     no-pty.  A	quote may be included in the command by	quoting	it
	     with a backslash.

	     This option might be useful to restrict certain public keys to
	     perform just a specific operation.	 An example might be a key
	     that permits remote backups but nothing else.  Note that the
	     client may	specify	TCP and/or X11 forwarding unless they are ex-
	     plicitly prohibited, e.g. using the restrict key option.

	     The command originally supplied by	the client is available	in the
	     SSH_ORIGINAL_COMMAND environment variable.	 Note that this	option
	     applies to	shell, command or subsystem execution.	Also note that
	     this command may be superseded by a sshd_config(5)	ForceCommand
	     directive.

	     If	a command is specified and a forced-command is embedded	in a
	     certificate used for authentication, then the certificate will be
	     accepted only if the two commands are identical.

     environment="NAME=value"
	     Specifies that the	string is to be	added to the environment when
	     logging in	using this key.	 Environment variables set this	way
	     override other default environment	values.	 Multiple options of
	     this type are permitted.  Environment processing is disabled by
	     default and is controlled via the PermitUserEnvironment option.

     expiry-time="timespec"
	     Specifies a time after which the key will not be accepted.	 The
	     time may be specified as a	YYYYMMDD date or a YYYYMMDDHHMM[SS]
	     time in the system	time-zone.

     from="pattern-list"
	     Specifies that in addition	to public key authentication, either
	     the canonical name	of the remote host or its IP address must be
	     present in	the comma-separated list of patterns.  See PATTERNS in
	     ssh_config(5) for more information	on patterns.

	     In	addition to the	wildcard matching that may be applied to host-
	     names or addresses, a from	stanza may match IP addresses using
	     CIDR address/masklen notation.

	     The purpose of this option	is to optionally increase security:
	     public key	authentication by itself does not trust	the network or
	     name servers or anything (but the key); however, if somebody
	     somehow steals the	key, the key permits an	intruder to log	in
	     from anywhere in the world.  This additional option makes using a
	     stolen key	more difficult (name servers and/or routers would have
	     to	be compromised in addition to just the key).

     no-agent-forwarding
	     Forbids authentication agent forwarding when this key is used for
	     authentication.

     no-port-forwarding
	     Forbids TCP forwarding when this key is used for authentication.
	     Any port forward requests by the client will return an error.
	     This might	be used, e.g. in connection with the command option.

     no-pty  Prevents tty allocation (a	request	to allocate a pty will fail).

     no-user-rc
	     Disables execution	of ~/.ssh/rc.

     no-X11-forwarding
	     Forbids X11 forwarding when this key is used for authentication.
	     Any X11 forward requests by the client will return	an error.

     permitlisten="[host:]port"
	     Limit remote port forwarding with the ssh(1) -R option such that
	     it	may only listen	on the specified host (optional) and port.
	     IPv6 addresses can	be specified by	enclosing the address in
	     square brackets.  Multiple	permitlisten options may be applied
	     separated by commas.  Hostnames may include wildcards as de-
	     scribed in	the PATTERNS section in	ssh_config(5).	A port speci-
	     fication of * matches any port.  Note that	the setting of
	     GatewayPorts may further restrict listen addresses.  Note that
	     ssh(1) will send a	hostname of "localhost"	if a listen host was
	     not specified when	the forwarding was requested, and that this
	     name is treated differently to the	explicit localhost addresses
	     "127.0.0.1" and "::1".

     permitopen="host:port"
	     Limit local port forwarding with the ssh(1) -L option such	that
	     it	may only connect to the	specified host and port.  IPv6 ad-
	     dresses can be specified by enclosing the address in square
	     brackets.	Multiple permitopen options may	be applied separated
	     by	commas.	 No pattern matching is	performed on the specified
	     hostnames,	they must be literal domains or	addresses.  A port
	     specification of *	matches	any port.

     port-forwarding
	     Enable port forwarding previously disabled	by the restrict	op-
	     tion.

     principals="principals"
	     On	a cert-authority line, specifies allowed principals for	cer-
	     tificate authentication as	a comma-separated list.	 At least one
	     name from the list	must appear in the certificate's list of prin-
	     cipals for	the certificate	to be accepted.	 This option is	ig-
	     nored for keys that are not marked	as trusted certificate signers
	     using the cert-authority option.

     pty     Permits tty allocation previously disabled	by the restrict	op-
	     tion.

     restrict
	     Enable all	restrictions, i.e. disable port, agent and X11 for-
	     warding, as well as disabling PTY allocation and execution	of
	     ~/.ssh/rc.	 If any	future restriction capabilities	are added to
	     authorized_keys files they	will be	included in this set.

     tunnel="n"
	     Force a tun(4) device on the server.  Without this	option,	the
	     next available device will	be used	if the client requests a tun-
	     nel.

     user-rc
	     Enables execution of ~/.ssh/rc previously disabled	by the
	     restrict option.

     X11-forwarding
	     Permits X11 forwarding previously disabled	by the restrict	op-
	     tion.

     An	example	authorized_keys	file:

	# Comments allowed at start of line
	ssh-rsa	AAAAB3Nza...LiPk== user@example.net
	from="*.sales.example.net,!pc.sales.example.net" ssh-rsa
	AAAAB2...19Q== john@example.net
	command="dump /home",no-pty,no-port-forwarding ssh-rsa
	AAAAC3...51R== example.net
	permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-rsa
	AAAAB5...21S==
	permitlisten="localhost:8080",permitopen="localhost:22000" ssh-rsa
	AAAAB5...21S==
	tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...==
	jane@example.net
	restrict,command="uptime" ssh-rsa AAAA1C8...32Tv==
	user@example.net
	restrict,pty,command="nethack" ssh-rsa AAAA1f8...IrrC5==
	user@example.net

SSH_KNOWN_HOSTS	FILE FORMAT
     The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host
     public keys for all known hosts.  The global file should be prepared by
     the administrator (optional), and the per-user file is maintained auto-
     matically:	whenever the user connects to an unknown host, its key is
     added to the per-user file.

     Each line in these	files contains the following fields: markers (op-
     tional), hostnames, keytype, base64-encoded key, comment.	The fields are
     separated by spaces.

     The marker	is optional, but if it is present then it must be one of
     "@cert-authority",	to indicate that the line contains a certification au-
     thority (CA) key, or "@revoked", to indicate that the key contained on
     the line is revoked and must not ever be accepted.	 Only one marker
     should be used on a key line.

     Hostnames is a comma-separated list of patterns (`*' and `?' act as wild-
     cards); each pattern in turn is matched against the host name.  When sshd
     is	authenticating a client, such as when using HostbasedAuthentication,
     this will be the canonical	client host name.  When	ssh(1) is authenticat-
     ing a server, this	will be	the host name given by the user, the value of
     the ssh(1)	HostkeyAlias if	it was specified, or the canonical server
     hostname if the ssh(1) CanonicalizeHostname option	was used.

     A pattern may also	be preceded by `!' to indicate negation: if the	host
     name matches a negated pattern, it	is not accepted	(by that line) even if
     it	matched	another	pattern	on the line.  A	hostname or address may	op-
     tionally be enclosed within `[' and `]' brackets then followed by `:' and
     a non-standard port number.

     Alternately, hostnames may	be stored in a hashed form which hides host
     names and addresses should	the file's contents be disclosed.  Hashed
     hostnames start with a `|'	character.  Only one hashed hostname may ap-
     pear on a single line and none of the above negation or wildcard opera-
     tors may be applied.

     The keytype and base64-encoded key	are taken directly from	the host key;
     they can be obtained, for example,	from /etc/ssh/ssh_host_rsa_key.pub.
     The optional comment field	continues to the end of	the line, and is not
     used.

     Lines starting with `#' and empty lines are ignored as comments.

     When performing host authentication, authentication is accepted if	any
     matching line has the proper key; either one that matches exactly or, if
     the server	has presented a	certificate for	authentication,	the key	of the
     certification authority that signed the certificate.  For a key to	be
     trusted as	a certification	authority, it must use the "@cert-authority"
     marker described above.

     The known hosts file also provides	a facility to mark keys	as revoked,
     for example when it is known that the associated private key has been
     stolen.  Revoked keys are specified by including the "@revoked" marker at
     the beginning of the key line, and	are never accepted for authentication
     or	as certification authorities, but instead will produce a warning from
     ssh(1) when they are encountered.

     It	is permissible (but not	recommended) to	have several lines or differ-
     ent host keys for the same	names.	This will inevitably happen when short
     forms of host names from different	domains	are put	in the file.  It is
     possible that the files contain conflicting information; authentication
     is	accepted if valid information can be found from	either file.

     Note that the lines in these files	are typically hundreds of characters
     long, and you definitely don't want to type in the	host keys by hand.
     Rather, generate them by a	script,	ssh-keyscan(1) or by taking, for exam-
     ple, /etc/ssh/ssh_host_rsa_key.pub	and adding the host names at the
     front.  ssh-keygen(1) also	offers some basic automated editing for
     ~/.ssh/known_hosts	including removing hosts matching a host name and con-
     verting all host names to their hashed representations.

     An	example	ssh_known_hosts	file:

	# Comments allowed at start of line
	closenet,...,192.0.2.53	1024 37	159...93 closenet.example.net
	cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
	# A hashed hostname
	|1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
	AAAA1234.....=
	# A revoked key
	@revoked * ssh-rsa AAAAB5W...
	# A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
	@cert-authority	*.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...

FILES
     ~/.hushlogin
	     This file is used to suppress printing the	last login time	and
	     /etc/motd,	if PrintLastLog	and PrintMotd, respectively, are en-
	     abled.  It	does not suppress printing of the banner specified by
	     Banner.

     ~/.rhosts
	     This file is used for host-based authentication (see ssh(1) for
	     more information).	 On some machines this file may	need to	be
	     world-readable if the user's home directory is on an NFS parti-
	     tion, because sshd	reads it as root.  Additionally, this file
	     must be owned by the user,	and must not have write	permissions
	     for anyone	else.  The recommended permission for most machines is
	     read/write	for the	user, and not accessible by others.

     ~/.shosts
	     This file is used in exactly the same way as .rhosts, but allows
	     host-based	authentication without permitting login	with
	     rlogin/rsh.

     ~/.ssh/
	     This directory is the default location for	all user-specific con-
	     figuration	and authentication information.	 There is no general
	     requirement to keep the entire contents of	this directory secret,
	     but the recommended permissions are read/write/execute for	the
	     user, and not accessible by others.

     ~/.ssh/authorized_keys
	     Lists the public keys (DSA, ECDSA,	Ed25519, RSA) that can be used
	     for logging in as this user.  The format of this file is de-
	     scribed above.  The content of the	file is	not highly sensitive,
	     but the recommended permissions are read/write for	the user, and
	     not accessible by others.

	     If	this file, the ~/.ssh directory, or the	user's home directory
	     are writable by other users, then the file	could be modified or
	     replaced by unauthorized users.  In this case, sshd will not al-
	     low it to be used unless the StrictModes option has been set to
	     "no".

     ~/.ssh/environment
	     This file is read into the	environment at login (if it exists).
	     It	can only contain empty lines, comment lines (that start	with
	     `#'), and assignment lines	of the form name=value.	 The file
	     should be writable	only by	the user; it need not be readable by
	     anyone else.  Environment processing is disabled by default and
	     is	controlled via the PermitUserEnvironment option.

     ~/.ssh/known_hosts
	     Contains a	list of	host keys for all hosts	the user has logged
	     into that are not already in the systemwide list of known host
	     keys.  The	format of this file is described above.	 This file
	     should be writable	only by	root/the owner and can,	but need not
	     be, world-readable.

     ~/.ssh/rc
	     Contains initialization routines to be run	before the user's home
	     directory becomes accessible.  This file should be	writable only
	     by	the user, and need not be readable by anyone else.

     /etc/hosts.allow
     /etc/hosts.deny
	     Access controls that should be enforced by	tcp-wrappers are de-
	     fined here.  Further details are described	in hosts_access(5).

     /etc/hosts.equiv
	     This file is for host-based authentication	(see ssh(1)).  It
	     should only be writable by	root.

     /etc/moduli
	     Contains Diffie-Hellman groups used for the "Diffie-Hellman Group
	     Exchange" key exchange method.  The file format is	described in
	     moduli(5).	 If no usable groups are found in this file then fixed
	     internal groups will be used.

     /etc/motd
	     See motd(5).

     /etc/nologin
	     If	this file exists, sshd refuses to let anyone except root log
	     in.  The contents of the file are displayed to anyone trying to
	     log in, and non-root connections are refused.  The	file should be
	     world-readable.

     /etc/shosts.equiv
	     This file is used in exactly the same way as hosts.equiv, but al-
	     lows host-based authentication without permitting login with
	     rlogin/rsh.

     /etc/ssh/ssh_host_ecdsa_key
     /etc/ssh/ssh_host_ed25519_key
     /etc/ssh/ssh_host_rsa_key
	     These files contain the private parts of the host keys.  These
	     files should only be owned	by root, readable only by root,	and
	     not accessible to others.	Note that sshd does not	start if these
	     files are group/world-accessible.

     /etc/ssh/ssh_host_ecdsa_key.pub
     /etc/ssh/ssh_host_ed25519_key.pub
     /etc/ssh/ssh_host_rsa_key.pub
	     These files contain the public parts of the host keys.  These
	     files should be world-readable but	writable only by root.	Their
	     contents should match the respective private parts.  These	files
	     are not really used for anything; they are	provided for the con-
	     venience of the user so their contents can	be copied to known
	     hosts files.  These files are created using ssh-keygen(1).

     /etc/ssh/ssh_known_hosts
	     Systemwide	list of	known host keys.  This file should be prepared
	     by	the system administrator to contain the	public host keys of
	     all machines in the organization.	The format of this file	is de-
	     scribed above.  This file should be writable only by root/the
	     owner and should be world-readable.

     /etc/ssh/sshd_config
	     Contains configuration data for sshd.  The	file format and	con-
	     figuration	options	are described in sshd_config(5).

     /etc/ssh/sshrc
	     Similar to	~/.ssh/rc, it can be used to specify machine-specific
	     login-time	initializations	globally.  This	file should be
	     writable only by root, and	should be world-readable.

     /var/empty
	     chroot(2) directory used by sshd during privilege separation in
	     the pre-authentication phase.  The	directory should not contain
	     any files and must	be owned by root and not group or world-
	     writable.

     /var/run/sshd.pid
	     Contains the process ID of	the sshd listening for connections (if
	     there are several daemons running concurrently for	different
	     ports, this contains the process ID of the	one started last).
	     The content of this file is not sensitive;	it can be world-read-
	     able.

SEE ALSO
     scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1),	ssh-keygen(1),
     ssh-keyscan(1), chroot(2),	hosts_access(5), login.conf(5),	moduli(5),
     sshd_config(5), inetd(8), sftp-server(8)

AUTHORS
     OpenSSH is	a derivative of	the original and free ssh 1.2.12 release by
     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
     de	Raadt and Dug Song removed many	bugs, re-added newer features and cre-
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.  Niels Provos and Markus Friedl contributed support
     for privilege separation.

BSD				 July 22, 2018				   BSD

NAME | SYNOPSIS | DESCRIPTION | AUTHENTICATION | LOGIN PROCESS | SSHRC | AUTHORIZED_KEYS FILE FORMAT | SSH_KNOWN_HOSTS FILE FORMAT | FILES | SEE ALSO | AUTHORS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=sshd&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help