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

NAME
     ssh-agent – authentication agent

SYNOPSIS
     ssh-agent [-c | -s] [-k] [command [args ...]]

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

     The options are as follows:

     -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
             variable).

     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
     $HOME/.ssh/identity file.  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 running without X).  It then sends the
     identity to the agent.  Several identities 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
     terminal.  Authentication data need not be stored on any other machine,
     and authentication passphrases never go over the network.  However, the
     connection to the agent is forwarded over SSH remote logins, and the user
     can thus use the privileges given by the identities anywhere in the
     network in a secure way.

     There are two main ways to get an agent setup: Either you let the agent
     start a new subcommand into which some environment variables are
     exported, or you let the agent print 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) look at these variables and use them to
     establish a connection to the agent.

     A unix-domain socket is created (/tmp/ssh-XXXXXXXX/agent.<pid>), 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 another instance of the same user.

     The SSH_AGENT_PID environment variable holds the agent's PID.

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

FILES
     $HOME/.ssh/identity
             Contains the RSA authentication identity of the user.  This file
             should not be readable by anyone but the user.  It is possible to
             specify a passphrase when generating the key; that passphrase
             will be used to encrypt the private part of this file.  This file
             is not used by ssh-agent but is normally added to the agent using
             ssh-add(1) at login time.

     /tmp/ssh-XXXX/agent.<pid>,
             Unix-domain sockets used to contain the connection to the
             authentication agent.  These sockets should only be readable by
             the owner.  The sockets should get automatically removed when the
             agent exits.

AUTHOR
     Tatu Ylonen <ylo@cs.hut.fi>

     OpenSSH is a derivative of the original (free) ssh 1.2.12 release, but
     with bugs removed and newer features re-added.  Rapidly after the 1.2.12
     release, newer versions bore successively more restrictive licenses.
     This version of OpenSSH

     •   has all components of a restrictive nature (i.e., patents, see
         ssl(8)) directly removed from the source code; any licensed or
         patented components are chosen from external libraries.

     •   has been updated to support ssh protocol 1.5.

     •   contains added support for kerberos(8) authentication and ticket
         passing.

     •   supports one-time password authentication with skey(1).

     The libraries described in ssl(8) are required for proper operation.

SEE ALSO
     ssh(1), ssh-add(1), ssh-keygen(1), sshd(8), ssl(8)

BSD                           September 25, 1999                           BSD