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SSH-AGENT(1)		  BSD General Commands Manual		  SSH-AGENT(1)

     ssh-agent -- authentication agent

     ssh-agent [-a bind_address] [-c | -s] [-d]	[command [args ...]]
     ssh-agent [-c | -s] -k

     ssh-agent is a program to hold private keys used for public key authenti-
     cation (RSA, DSA).	 The idea is that ssh-agent is started in the begin-
     ning of an	X-session or a login session, and all other windows or pro-
     grams are started as clients to the ssh-agent program.  Through use of
     environment variables the agent can be located and	automatically used for
     authentication when logging in to other machines using ssh(1).

     The options are as	follows:

     -a	bind_address
	     Bind the agent to the unix-domain socket bind_address.  The de-
	     fault is /tmp/ssh-XXXXXXXX/agent._ppid_.

     -c	     Generate C-shell commands on stdout.  This	is the default if
	     SHELL looks like it's a csh style of shell.

     -s	     Generate Bourne shell commands on stdout.	This is	the default if
	     SHELL does	not look like it's a csh style of shell.

     -k	     Kill the current agent (given by the SSH_AGENT_PID	environment

     -d	     Debug mode.  When this option is specified	ssh-agent will not

     If	a commandline is given,	this is	executed as a subprocess of the	agent.
     When the command dies, so does the	agent.

     The agent initially does not have any private keys.  Keys are added using
     ssh-add(1).  When executed	without	arguments, ssh-add(1) adds the files
     $HOME/.ssh/id_rsa,	$HOME/.ssh/id_dsa and $HOME/.ssh/identity.  If the
     identity has a passphrase,	ssh-add(1) asks	for the	passphrase (using a
     small X11 application if running under X11, or from the terminal if run-
     ning without X).  It then sends the identity to the agent.	 Several iden-
     tities can	be stored in the agent;	the agent can automatically use	any of
     these identities.	ssh-add	-l displays the	identities currently held by
     the agent.

     The idea is that the agent	is run in the user's local PC, laptop, or ter-
     minal.  Authentication data need not be stored on any other machine, and
     authentication passphrases	never go over the network.  However, the con-
     nection to	the agent is forwarded over SSH	remote logins, and the user
     can thus use the privileges given by the identities anywhere in the net-
     work in a secure way.

     There are two main	ways to	get an agent setup: Either the agent starts a
     new subcommand into which some environment	variables are exported,	or the
     agent prints the needed shell commands (either sh(1) or csh(1) syntax can
     be	generated) which can be	evalled	in the calling shell.  Later ssh(1)
     looks at these variables and uses them to establish a connection to the

     The agent will never send a private key over its request channel.	In-
     stead, operations that require a private key will be performed by the
     agent, and	the result will	be returned to the requester.  This way, pri-
     vate keys are not exposed to clients using	the agent.

     A unix-domain socket is created and the name of this socket is stored in
     the SSH_AUTH_SOCK environment variable.  The socket is made accessible
     only to the current user.	This method is easily abused by	root or	an-
     other instance of the same	user.

     The SSH_AGENT_PID environment variable holds the agent's process ID.

     The agent exits automatically when	the command given on the command line

	     Contains the protocol version 1 RSA authentication	identity of
	     the user.

	     Contains the protocol version 2 DSA authentication	identity of
	     the user.

	     Contains the protocol version 2 RSA authentication	identity of
	     the user.

	     Unix-domain sockets used to contain the connection	to the authen-
	     tication agent.  These sockets should only	be readable by the
	     owner.  The sockets should	get automatically removed when the
	     agent exits.

     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.

     ssh(1), ssh-add(1), ssh-keygen(1),	sshd(8)

BSD			      September	25, 1999			   BSD


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