.Op Ar command
.Pp
.Nm ssh
-.Op Fl afgknqtvxCPX
+.Op Fl afgknqtvxCPX46
.Op Fl c Ar blowfish | 3des
.Op Fl e Ar escape_char
.Op Fl i Ar identity_file
.Op Fl p Ar port
.Oo Fl L Xo
.Sm off
-.Ar host :
.Ar port :
+.Ar host :
.Ar hostport
.Sm on
.Xc
.Oc
.Oo Fl R Xo
.Sm off
-.Ar host :
.Ar port :
+.Ar host :
.Ar hostport
.Sm on
.Xc
First, if the machine the user logs in from is listed in
.Pa /etc/hosts.equiv
or
-.Pa /etc/ssh/shosts.equiv
+.Pa /etc/shosts.equiv
on the remote machine, and the user names are
the same on both sides, the user is immediately permitted to log in.
Second, if
.Pa \&.shosts ,
.Pa /etc/hosts.equiv ,
or
-.Pa /etc/ssh/shosts.equiv ,
+.Pa /etc/shosts.equiv ,
and if additionally the server can verify the client's
host key (see
-.Pa /etc/ssh/ssh_known_hosts
+.Pa /etc/ssh_known_hosts
and
.Pa $HOME/.ssh/known_hosts
in the
database is stored in
.Pa \&.ssh/known_hosts
in the user's home directory. Additionally, the file
-.Pa /etc/ssh/ssh_known_hosts
+.Pa /etc/ssh_known_hosts
is automatically checked for known hosts. Any new hosts are
automatically added to the user's file. If a host's identification
ever changes,
.It Fl f
Requests
.Nm
-to go to background after authentication. This is useful
+to go to background just before command execution. This is useful
if
.Nm
is going to ask for passwords or passphrases, but the user
The recommended way to start X11 programs at a remote site is with
something like
.Ic ssh -f host xterm .
+.It Fl g
+Allows remote hosts to connect to local forwarded ports.
.It Fl i Ar identity_file
Selects the file from which the identity (private key) for
RSA authentication is read. Default is
.Fl i
options (and multiple identities specified in
configuration files).
-.It Fl g
-Allows remote hosts to connect to local forwarded ports.
.It Fl k
Disables forwarding of Kerberos tickets and AFS tokens. This may
also be specified on a per-host basis in the configuration file.
Use a non-privileged port for outgoing connections.
This can be used if your firewall does
not permit connections from privileged ports.
-Note that this option turns of
+Note that this option turns off
.Cm RhostsAuthentication
and
.Cm RhostsRSAAuthentication .
.It Fl C
Requests compression of all data (including stdin, stdout, stderr, and
data for forwarded X11 and TCP/IP connections). The compression
-algorithm is the same used by gzip, and the
+algorithm is the same used by
+.Xr gzip 1 ,
+and the
.Dq level
can be controlled by the
.Cm CompressionLevel
on the local side, and whenever a connection is made to this port, the
connection is forwarded over the secure channel, and a connection is
made to
-.Ar host:hostport
+.Ar host
+port
+.Ar hostport
from the remote machine. Port forwardings can also be specified in the
configuration file. Only root can forward privileged ports.
+IPv6 addresses can be specified with an alternative syntax:
+.Ar port/host/hostport
.It Fl R Ar port:host:hostport
Specifies that the given port on the remote (server) host is to be
forwarded to the given host and port on the local side. This works
on the remote side, and whenever a connection is made to this port, the
connection is forwarded over the secure channel, and a connection is
made to
-.Ar host:hostport
+.Ar host
+port
+.Ar hostport
from the local machine. Port forwardings can also be specified in the
configuration file. Privileged ports can be forwarded only when
logging in as root on the remote machine.
+.It Fl 4
+Forces
+.Nm
+to use IPv4 addresses only.
+.It Fl 6
+Forces
+.Nm
+to use IPv6 addresses only.
.El
.Sh CONFIGURATION FILES
.Nm
command line options, user's configuration file
.Pq Pa $HOME/.ssh/config ,
and system-wide configuration file
-.Pq Pa /etc/ssh/ssh_config .
+.Pq Pa /etc/ssh_config .
For each parameter, the first obtained value
will be used. The configuration files contain sections bracketed by
"Host" specifications, and that section is only applied for hosts that
.Dq yes
or
.Dq no .
+.It Cm CheckHostIP
+If this flag is set to
+.Dq yes ,
+ssh will additionally check the host ip address in the
+.Pa known_hosts
+file. This allows ssh to detect if a host key changed due to DNS spoofing.
+If the option is set to
+.Dq no ,
+the check will not be executed.
.It Cm Cipher
Specifies the cipher to use for encrypting the session. Currently,
.Dq blowfish ,
Specifies the compression level to use if compression is enable. The
argument must be an integer from 1 (fast) to 9 (slow, best). The
default level is 6, which is good for most applications. The meaning
-of the values is the same as in GNU GZIP.
+of the values is the same as in
+.Xr gzip 1 .
.It Cm ConnectionAttempts
Specifies the number of tries (one per second) to make before falling
back to rsh or exiting. The argument must be an integer. This may be
.Dq no .
.It Cm GlobalKnownHostsFile
Specifies a file to use instead of
-.Pa /etc/ssh/ssh_known_hosts .
+.Pa /etc/ssh_known_hosts .
.It Cm HostName
Specifies the real host name to log into. This can be used to specify
nicnames or abbreviations for hosts. Default is the name given on the
host:port. Multiple forwardings may be specified, and additional
forwardings can be given on the command line. Only the root can
forward privileged ports.
-.It Cm PasswordAuthentication
-Specifies whether to use password authentication. The argument to
-this keyword must be
-.Dq yes
-or
-.Dq no .
.It Cm LogLevel
Gives the verbosity level that is used when logging messages from
.Nm ssh .
.It Cm NumberOfPasswordPrompts
Specifies the number of password prompts before giving up. The
argument to this keyword must be an integer. Default is 3.
+.It Cm PasswordAuthentication
+Specifies whether to use password authentication. The argument to
+this keyword must be
+.Dq yes
+or
+.Dq no .
.It Cm Port
Specifies the port number to connect on the remote host. Default is
22.
somewhere. Host key management will be done using the
HostName of the host being connected (defaulting to the name typed by
the user).
+Note that
+.Cm CheckHostIP
+is not available for connects with a proxy command.
.Pp
.It Cm RemoteForward
Specifies that a TCP/IP port on the remote machine be forwarded over
RSA authentication will only be
attempted if the identity file exists, or an authentication agent is
running.
-.It Cm CheckHostIP
-If this flag is set to
-.Dq yes ,
-ssh will additionally check the host ip address in the
-.Pa known_hosts
-file. This allows ssh to detect if a host key changed due to DNS spoofing.
-If the option is set to
-.Dq no ,
-the check will not be executed.
+.It Cm SkeyAuthentication
+Specifies whether to use
+.Xr skey 1
+authentication. The argument to
+this keyword must be
+.Dq yes
+or
+.Dq no .
+The default is
+.Dq no .
.It Cm StrictHostKeyChecking
If this flag is set to
.Dq yes ,
file, and refuses to connect hosts whose host key has changed. This
provides maximum protection against trojan horse attacks. However, it
can be somewhat annoying if you don't have good
-.Pa /etc/ssh/ssh_known_hosts
+.Pa /etc/ssh_known_hosts
files installed and frequently
connect new hosts. Basically this option forces the user to manually
add any new hosts. Normally this option is disabled, and new hosts
.Dq yes
or
.Dq no .
-.It Cm User
-Specifies the user to log in as. This can be useful if you have a
-different user name in different machines. This saves the trouble of
-having to remember to give the user name on the command line.
-.It Cm UserKnownHostsFile
-Specifies a file to use instead of
-.Pa $HOME/.ssh/known_hosts .
.It Cm UsePrivilegedPort
Specifies whether to use a privileged port for outgoing connections.
The argument must be
.Dq yes .
Note that setting this option to
.Dq no
-turns of
+turns off
.Cm RhostsAuthentication
and
.Cm RhostsRSAAuthentication .
+.It Cm User
+Specifies the user to log in as. This can be useful if you have a
+different user name in different machines. This saves the trouble of
+having to remember to give the user name on the command line.
+.It Cm UserKnownHostsFile
+Specifies a file to use instead of
+.Pa $HOME/.ssh/known_hosts .
.It Cm UseRsh
Specifies that rlogin/rsh should be used for this host. It is
possible that the host does not at all support the
.It Pa $HOME/.ssh/known_hosts
Records host keys for all hosts the user has logged into (that are not
in
-.Pa /etc/ssh/ssh_known_hosts ) .
+.Pa /etc/ssh_known_hosts ) .
See
.Xr sshd 8 .
-.It Pa $HOME/.ssh/random_seed
-Used for seeding the random number generator. This file contains
-sensitive data and should read/write for the user and not accessible
-for others. This file is created the first time the program is run
-and updated automatically. The user should never need to read or
-modify this file.
.It Pa $HOME/.ssh/identity
Contains the RSA authentication identity of the user. This file
contains sensitive data and should be readable by the user but not
modulus, public exponent, modulus, and comment fields, separated by
spaces). This file is not highly sensitive, but the recommended
permissions are read/write for the user, and not accessible by others.
-.It Pa /etc/ssh/ssh_known_hosts
+.It Pa /etc/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. This file should be world-readable. This file contains
does not convert the user-supplied name to a canonical name before
checking the key, because someone with access to the name servers
would then be able to fool host authentication.
-.It Pa /etc/ssh/ssh_config
+.It Pa /etc/ssh_config
Systemwide configuration file. This file provides defaults for those
values that are not specified in the user's configuration file, and
for those users who do not have a configuration file. This file must
will be installed so that it requires successful RSA host
authentication before permitting \s+2.\s0rhosts authentication. If your
server machine does not have the client's host key in
-.Pa /etc/ssh/ssh_known_hosts ,
+.Pa /etc/ssh_known_hosts ,
you can store it in
.Pa $HOME/.ssh/known_hosts .
The easiest way to do this is to
automatically permitted provided client and server user names are the
same. Additionally, successful RSA host authentication is normally
required. This file should only be writable by root.
-.It Pa /etc/ssh/shosts.equiv
+.It Pa /etc/shosts.equiv
This file is processed exactly as
.Pa /etc/hosts.equiv .
This file may be useful to permit logins using
.Nm
but not using rsh/rlogin.
-.It Pa /etc/ssh/sshrc
+.It Pa /etc/sshrc
Commands in this file are executed by
.Nm
when the user logs in just before the user's shell (or command) is started.
See the
.Xr sshd 8
manual page for more information.
+.It Pa $HOME/.ssh/environment
+Contains additional definitions for environment variables, see section
+.Sx ENVIRONMENT
+above.
.It Pa libcrypto.so.X.1
A version of this library which includes support for the RSA algorithm
is required for proper operation.
The libraries described in
.Xr ssl 8
are required for proper operation.
+.Pp
+OpenSSH has been created by Aaron Campbell, Bob Beck, Markus Friedl,
+Niels Provos, Theo de Raadt, and Dug Song.
.Sh SEE ALSO
.Xr rlogin 1 ,
.Xr rsh 1 ,
andersk / openssh.git / blobdiff