ssh-agent.1(1)

     NAME
          ssh-agent - authentication agent

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

     DESCRIPTION
          ssh-agent is a program to hold private keys used for public
          key authentication (RSA, DSA).  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 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 default 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 variable).

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

               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 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
               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 agent.

               The agent will never send a private key over its
               request channel.  Instead, operations that require a
               private key will be performed by the agent, and the
               result will be returned to the requester.  This way,
               private 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
               another 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 terminates.

     FILES
          $HOME/.ssh/identity
               Contains the protocol version 1 RSA authentication
               identity of the user.

          $HOME/.ssh/id_dsa
               Contains the protocol version 2 DSA authentication
               identity of the user.

          $HOME/.ssh/id_rsa
               Contains the protocol version 2 RSA authentication
               identity of the user.

          /tmp/ssh-XXXXXXXX/agent.<ppid>
               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.

     AUTHORS
          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 created OpenSSH.
          Markus Friedl contributed the support for SSH protocol
          versions 1.5 and 2.0.

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