Here is a quick script addition to our .bashrc file which will start a ssh-agent once and load the proper environment variables for the other terminal you will sub-sequentially open. 

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test=`/bin/ps -ef | /bin/grep ssh-agent | /bin/grep ${USER} | /usr/bin/awk '{print $2}' | xargs`

if [ ! -e "$HOME/agent.sh" -o "$test" = "" ]; then
   if [ ! -e "$HOME/agent.sh" -a "$test" != "" ]; then
      kill -9 ${test}
   else  
      /usr/bin/test -e $HOME/agent.sh && /bin/rm -f $HOME/agent.sh
   fi; 
   /usr/bin/ssh-agent >&$HOME/agent.sh.tmp && \
     /bin/sed "s/echo/#echo/" $HOME/agent.sh.tmp >$HOME/agent.sh && \
     /bin/rm -f $HOME/agent.sh.tmp
fi;

/usr/bin/test -e $HOME/agent.sh && source $HOME/agent.sh

alias kagent="kill -9 $SSH_AGENT_PID"

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Tips

• Most trivial remark: the above is a SH script and it sources the agent.sh - please verify that ssh-agent output sh commands (and not csh commands). If your system global default shell is bash or sh, this will be true.
   
• If you use this script, please use

  % ssh-add -L
  

  to check if keys are already upload or load them using the same command. ssh-add cannot be automated in .bashrc since it will prompt for your passphrase.

• Note that the file agent.sh resides in your home directory. If on any terminal, ssh-add tells you

      Could not open a connection to your authenticated agent    

  then source agent.sh and try again
   
• Starting an agent automatically in this manner implies that ANYONE having access to your machine, laptop could access your remote accounts without having to type a password. You MUST understand this includes automated command executed on your behalf. To minimize this risk, consider the following:
  • Be careful of the use of an agent on a node which is not a personal laptop or computer. If multiple people have access to the machine, consider it a NO start.
  • If you do start an agent, upload your keys when needed. You may destroy your keys by using the

    % ssh-add -D
    

    command. You may also destroy the agent (which will have the same effect).
     
• The command kagent has been defined above to kill the first agent detached via this method.
   
• To make sure -A option is implicit while using ssh (and/or -X) consult Caveats, issues, special cases and possible problems for further information on tweaking your client side $HOME/.ssh/config .
  

 PLease, le me know if this script causes problems and your suggestion to improve.