ssh-agent

 

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 SSH-AGENT(1)            System General Commands Manual            SSH-AGENT(1)
 
 NAME
      ssh-agent - authentication agent
 
 SYNOPSIS
      ssh-agent command args ...
      ssh-agent [-c | -s]
      ssh-agent -k
 
 DESCRIPTION
      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:
 
      -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 iden­
      tity 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 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 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) looks at these variables and uses 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 protocol version 1 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.
 
      $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.<pid>
              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.
 
 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 cre­
      ated 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)
 
 BSD                           September 25, 1999                           BSD

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