+.Xr services 5 ) .
+The
+.Fl debug
+option may be used to start up
+.Nm telnetd
+manually, instead of through
+.Xr inetd 8 .
+If started up this way,
+.Ar port
+may be specified to run
+.Nm telnetd
+on an alternate
+.Tn TCP
+port number.
+.Pp
+The
+.Nm telnetd
+command accepts the following options:
+.Bl -tag -width "-a authmode"
+.It Fl a Ar authmode
+This option may be used for specifying what mode should
+be used for authentication.
+Note that this option is only useful if
+.Nm telnetd
+has been compiled with support for the
+.Dv AUTHENTICATION
+option.
+There are several valid values for
+.Ar authmode:
+.Bl -tag -width debug
+.It debug
+Turns on authentication debugging code.
+.It user
+Only allow connections when the remote user
+can provide valid authentication information
+to identify the remote user,
+and is allowed access to the specified account
+without providing a password.
+.It valid
+Only allow connections when the remote user
+can provide valid authentication information
+to identify the remote user.
+The
+.Xr login 1
+command will provide any additional user verification
+needed if the remote user is not allowed automatic
+access to the specified account.
+.It other
+Only allow connections that supply some authentication information.
+This option is currently not supported
+by any of the existing authentication mechanisms,
+and is thus the same as specifying
+.Fl a
+.Cm valid .
+.It none
+This is the default state.
+Authentication information is not required.
+If no or insufficient authentication information
+is provided, then the
+.Xr login 1
+program will provide the necessary user
+verification.
+.It off
+This disables the authentication code.
+All user verification will happen through the
+.Xr login 1
+program.
+.El
+.It Fl B
+Specifies bftp server mode. In this mode,
+.Nm telnetd
+causes login to start a
+.Xr bftp 1
+session rather than the user's
+normal shell. In bftp daemon mode normal
+logins are not supported, and it must be used
+on a port other than the normal
+.Tn TELNET
+port.
+.It Fl D Ar debugmode
+This option may be used for debugging purposes.
+This allows
+.Nm telnetd
+to print out debugging information
+to the connection, allowing the user to see what
+.Nm telnetd
+is doing.
+There are several possible values for
+.Ar debugmode:
+.Bl -tag -width exercise
+.It Cm options
+Prints information about the negotiation of
+.Tn TELNET
+options.
+.It Cm report
+Prints the
+.Cm options
+information, plus some additional information
+about what processing is going on.
+.It Cm netdata
+Displays the data stream received by
+.Nm telnetd.
+.It Cm ptydata
+Displays data written to the pty.
+.It Cm exercise
+Has not been implemented yet.
+.El
+.It Fl debug
+Enables debugging on each socket created by
+.Nm telnetd
+(see
+.Dv SO_DEBUG
+in
+.Xr socket 2 ) .
+.It Fl edebug
+If
+.Nm telnetd
+has been compiled with support for data encryption, then the
+.Fl edebug
+option may be used to enable encryption debugging code.
+.It Fl h
+Disables the printing of host-specific information before
+login has been completed.
+.It Fl I Ar initid
+This option is only applicable to
+.Tn UNICOS
+systems prior to 7.0.
+It specifies the
+.Dv ID
+from
+.Pa /etc/inittab
+to use when init starts login sessions. The default
+.Dv ID
+is
+.Dv fe.
+.It Fl k
+This option is only useful if
+.Nm telnetd
+has been compiled with both linemode and kludge linemode
+support. If the
+.Fl k
+option is specified, then if the remote client does not
+support the
+.Dv LINEMODE
+option, then
+.Nm telnetd
+will operate in character at a time mode.
+It will still support kludge linemode, but will only
+go into kludge linemode if the remote client requests
+it.
+(This is done by by the client sending
+.Dv DONT SUPPRESS-GO-AHEAD
+and
+.Dv DONT ECHO . )
+The
+.Fl k
+option is most useful when there are remote clients
+that do not support kludge linemode, but pass the heuristic
+(if they respond with
+.Dv WILL TIMING-MARK
+in response to a
+.Dv DO TIMING-MARK)
+for kludge linemode support.
+.It Fl l
+Specifies line mode. Tries to force clients to use line-
+at-a-time mode.
+If the
+.Dv LINEMODE
+option is not supported, it will go
+into kludge linemode.
+.It Fl n
+Disable
+.Dv TCP
+keep-alives. Normally
+.Nm telnetd
+enables the
+.Tn TCP
+keep-alive mechanism to probe connections that
+have been idle for some period of time to determine
+if the client is still there, so that idle connections
+from machines that have crashed or can no longer
+be reached may be cleaned up.
+.It Fl r Ar lowpty-highpty
+This option is only enabled when
+.Nm telnetd
+is compiled for
+.Dv UNICOS.
+It specifies an inclusive range of pseudo-terminal devices to
+use. If the system has sysconf variable
+.Dv _SC_CRAY_NPTY
+configured, the default pty search range is 0 to
+.Dv _SC_CRAY_NPTY;
+otherwise, the default range is 0 to 128. Either
+.Ar lowpty
+or
+.Ar highpty
+may be omitted to allow changing
+either end of the search range. If
+.Ar lowpty
+is omitted, the - character is still required so that
+.Nm telnetd
+can differentiate
+.Ar highpty
+from
+.Ar lowpty .
+.It Fl s
+This option is only enabled if
+.Nm telnetd
+is compiled with support for
+.Tn SecurID
+cards.
+It causes the
+.Fl s
+option to be passed on to
+.Xr login 1 ,
+and thus is only useful if
+.Xr login 1
+supports the
+.Fl s
+flag to indicate that only
+.Tn SecurID
+validated logins are allowed, and is
+usually useful for controlling remote logins
+from outside of a firewall.
+.It Fl S Ar tos
+.It Fl u Ar len
+This option is used to specify the size of the field
+in the
+.Dv utmp
+structure that holds the remote host name.
+If the resolved host name is longer than
+.Ar len ,
+the dotted decimal value will be used instead.
+This allows hosts with very long host names that
+overflow this field to still be uniquely identified.
+Specifying
+.Fl u0
+indicates that only dotted decimal addresses
+should be put into the
+.Pa utmp
+file.
+.It Fl U
+This option causes
+.Nm telnetd
+to refuse connections from addresses that
+cannot be mapped back into a symbolic name
+via the
+.Xr gethostbyaddr 3
+routine.
+.It Fl X Ar authtype
+This option is only valid if
+.Nm telnetd
+has been built with support for the authentication option.
+It disables the use of
+.Ar authtype
+authentication, and
+can be used to temporarily disable
+a specific authentication type without having to recompile
+.Nm telnetd .
+.El
+.Pp
+.Nm Telnetd