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Diff for /src/usr.bin/ssh/ssh_config.5 between version 1.49 and 1.49.2.2

version 1.49, 2005/03/16 11:10:38

version 1.49.2.2, 2006/02/03 02:53:45

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.Nd OpenSSH SSH client configuration files

.Sh SYNOPSIS

.Bl -tag -width Ds -compact

.It Pa $HOME/.ssh/config

.It Pa ~/.ssh/config

.It Pa /etc/ssh/ssh_config

.El

.Sh DESCRIPTION

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command-line options

.It

user's configuration file

.Pq Pa $HOME/.ssh/config

.Pq Pa ~/.ssh/config

.It

system-wide configuration file

.Pq Pa /etc/ssh/ssh_config

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The default is

.Dq no .

.It Cm BindAddress

Specify the interface to transmit from on machines with multiple

Use the specified address on the local machine as the source address of

interfaces or aliased addresses.

the connection.

Only useful on systems with more than one address.

Note that this option does not work if

.Cm UsePrivilegedPort

is set to

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.Dq aes128-ctr ,

.Dq aes192-ctr ,

.Dq aes256-ctr ,

.Dq arcfour128 ,

.Dq arcfour256 ,

.Dq arcfour ,

.Dq blowfish-cbc ,

and

.Dq cast128-cbc .

The default is

.Bd -literal

``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,

``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,

aes192-cbc,aes256-cbc''

arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,

aes192-ctr,aes256-ctr''

.Ed

.It Cm ClearAllForwardings

Specifies that all local, remote and dynamic port forwardings

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set to

.Dq no

(the default).

These sessions will reuse the master instance's network connection rather

These sessions will try to reuse the master instance's network connection

than initiating new ones.

rather than initiating new ones, but will fall back to connecting normally

if the control socket does not exist, or is not listening.

.Pp

Setting this to

.Dq ask

will cause

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program before they are accepted (see

.Xr ssh-add 1

for details).

If the

.Cm ControlPath

can not be opened,

.Nm ssh

will continue without connecting to a master instance.

.Pp

X11 and

.Xr ssh-agent 1

forwarding is supported over these multiplexed connections, however the

display and agent forwarded will be the one belonging to the master

connection i.e. it is not possible to forward multiple displays or agents.

.Pp

Two additional options allow for opportunistic multiplexing: try to use a

master connection but fall back to creating a new one if one does not already

exist.

These options are:

.Dq auto

and

.Dq autoask .

The latter requires confirmation like the

.Dq ask

option.

.It Cm ControlPath

Specify the path to the control socket used for connection sharing.

Specify the path to the control socket used for connection sharing as described

See

in the

.Cm ControlMaster

above.

section above or the string

.Dq none

to disable connection sharing.

In the path,

.Ql %h

will be substituted by the target host name,

.Ql %p

the port and

.Ql %r

by the remote login username.

It is recommended that any

.Cm ControlPath

used for opportunistic connection sharing include

all three of these escape sequences.

This ensures that shared connections are uniquely identified.

.It Cm DynamicForward

Specifies that a TCP/IP port on the local machine be forwarded

Specifies that a TCP port on the local machine be forwarded

over the secure channel, and the application

protocol is then used to determine where to connect to from the

remote machine.

The argument must be a port number.

.Pp

The argument must be

.Sm off

.Oo Ar bind_address : Oc Ar port .

.Sm on

IPv6 addresses can be specified by enclosing addresses in square brackets or

by using an alternative syntax:

.Oo Ar bind_address Ns / Oc Ns Ar port .

By default, the local port is bound in accordance with the

.Cm GatewayPorts

setting.

However, an explicit

.Ar bind_address

may be used to bind the connection to a specific address.

The

.Ar bind_address

.Dq localhost

indicates that the listening port be bound for local use only, while an

empty address or

.Sq *

indicates that the port should be available from all interfaces.

.Pp

Currently the SOCKS4 and SOCKS5 protocols are supported, and

.Nm ssh

will act as a SOCKS server.

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Indicates that

.Nm ssh

should hash host names and addresses when they are added to

.Pa $HOME/.ssh/known_hosts .

.Pa ~/.ssh/known_hosts .

These hashed names may be used normally by

.Nm ssh

and

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Numeric IP addresses are also permitted (both on the command line and in

.Cm HostName

specifications).

.It Cm IdentityFile

Specifies a file from which the user's RSA or DSA authentication identity

is read.

The default is

.Pa $HOME/.ssh/identity

for protocol version 1, and

.Pa $HOME/.ssh/id_rsa

and

.Pa $HOME/.ssh/id_dsa

for protocol version 2.

Additionally, any identities represented by the authentication agent

will be used for authentication.

The file name may use the tilde

syntax to refer to a user's home directory.

It is possible to have

multiple identity files specified in configuration files; all these

identities will be tried in sequence.

.It Cm IdentitiesOnly

Specifies that

.Nm ssh

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.Dq yes

.Dq no .

This option is intented for situations where

This option is intended for situations where

.Nm ssh-agent

offers many different identities.

The default is

.Dq no .

.It Cm IdentityFile

Specifies a file from which the user's RSA or DSA authentication identity

is read.

The default is

.Pa ~/.ssh/identity

for protocol version 1, and

.Pa ~/.ssh/id_rsa

and

.Pa ~/.ssh/id_dsa

for protocol version 2.

Additionally, any identities represented by the authentication agent

will be used for authentication.

The file name may use the tilde

syntax to refer to a user's home directory.

It is possible to have

multiple identity files specified in configuration files; all these

identities will be tried in sequence.

.It Cm KbdInteractiveDevices

Specifies the list of methods to use in keyboard-interactive authentication.

Multiple method names must be comma-separated.

The default is to use the server specified list.

.It Cm LocalCommand

Specifies a command to execute on the local machine after successfully

connecting to the server.

The command string extends to the end of the line, and is executed with

.Pa /bin/sh .

This directive is ignored unless

.Cm PermitLocalCommand

has been enabled.

.It Cm LocalForward

Specifies that a TCP/IP port on the local machine be forwarded over

Specifies that a TCP port on the local machine be forwarded over

the secure channel to the specified host and port from the remote machine.

The first argument must be

.Sm off

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.Dq no .

The default is

.Dq yes .

.It Cm PermitLocalCommand

Allow local command execution via the

.Ic LocalCommand

option or using the

.Ic !\& Ns Ar command

escape sequence in

.Xr ssh 1 .

The argument must be

.Dq yes

.Dq no .

The default is

.Dq no .

.It Cm Port

Specifies the port number to connect on the remote host.

Default is 22.

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.Cm CheckHostIP

is not available for connects with a proxy command.

.Pp

This directive is useful in conjunction with

.Xr nc 1

and its proxy support.

For example, the following directive would connect via an HTTP proxy at

192.0.2.0:

.Bd -literal -offset 3n

ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p

.Ed

.It Cm PubkeyAuthentication

Specifies whether to try public key authentication.

The argument to this keyword must be

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The default is

.Dq yes .

This option applies to protocol version 2 only.

.It Cm RekeyLimit

Specifies the maximum amount of data that may be transmitted before the

session key is renegotiated.

The argument is the number of bytes, with an optional suffix of

.Sq K ,

.Sq M ,

.Sq G

to indicate Kilobytes, Megabytes, or Gigabytes, respectively.

The default is between

.Dq 1G

and

.Dq 4G ,

depending on the cipher.

This option applies to protocol version 2 only.

.It Cm RemoteForward

Specifies that a TCP/IP port on the remote machine be forwarded over

Specifies that a TCP port on the remote machine be forwarded over

the secure channel to the specified host and port from the local machine.

The first argument must be

.Sm off

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.Cm SendEnv

directives.

The default is not to send any environment variables.

.It Cm ServerAliveInterval

Sets a timeout interval in seconds after which if no data has been received

from the server,

.Nm ssh

will send a message through the encrypted

channel to request a response from the server.

The default

is 0, indicating that these messages will not be sent to the server.

This option applies to protocol version 2 only.

.It Cm ServerAliveCountMax

Sets the number of server alive messages (see above) which may be

Sets the number of server alive messages (see below) which may be

sent without

.Nm ssh

receiving any messages back from the server.

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The default value is 3.

If, for example,

.Cm ServerAliveInterval

(above) is set to 15, and

(see below) is set to 15, and

.Cm ServerAliveCountMax

is left at the default, if the server becomes unresponsive ssh

will disconnect after approximately 45 seconds.

.It Cm ServerAliveInterval

Sets a timeout interval in seconds after which if no data has been received

from the server,

.Nm ssh

will send a message through the encrypted

channel to request a response from the server.

The default

is 0, indicating that these messages will not be sent to the server.

This option applies to protocol version 2 only.

.It Cm SmartcardDevice

Specifies which smartcard device to use.

The argument to this keyword is the device

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.Dq yes ,

.Nm ssh

will never automatically add host keys to the

.Pa $HOME/.ssh/known_hosts

.Pa ~/.ssh/known_hosts

file, and refuses to connect to hosts whose host key has changed.

This provides maximum protection against trojan horse attacks,

however, can be annoying when the

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.Pp

To disable TCP keepalive messages, the value should be set to

.Dq no .

.It Cm Tunnel

Request starting

.Xr tun 4

device forwarding between the client and the server.

This option also allows requesting layer 2 (ethernet)

instead of layer 3 (point-to-point) tunneling from the server.

The argument must be

.Dq yes ,

.Dq point-to-point ,

.Dq ethernet

.Dq no .

The default is

.Dq no .

.It Cm TunnelDevice

Force a specified

.Xr tun 4

device on the client.

Without this option, the next available device will be used.

.It Cm UsePrivilegedPort

Specifies whether to use a privileged port for outgoing connections.

The argument must be

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.It Cm UserKnownHostsFile

Specifies a file to use for the user

host key database instead of

.Pa $HOME/.ssh/known_hosts .

.Pa ~/.ssh/known_hosts .

.It Cm VerifyHostKeyDNS

Specifies whether to verify the remote key using DNS and SSHFP resource

records.

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.El

.Sh FILES

.Bl -tag -width Ds

.It Pa $HOME/.ssh/config

.It Pa ~/.ssh/config

This is the per-user configuration file.

The format of this file is described above.

This file is used by the