technology

optimization of ssh-agent and ssh-add for git bash

Background

Several days ago, To use github, i installed git in my new laptop for the first time, and encountered a problem about management of ssh-agent and ssh keys.

After starting a new “git bash” terminal, there was something wrong when pushed my new commit, see below picture:

error

when used command “ssh-add -l” to check the private keys added, it returned an error, the key error message “Could not open a connection to your authentication agent” .

Resolution

After google, realized that “git bash” needs us to start the “ssh-agent” process before “ssh-add” and “git” command using ssh protocol.

resolution in StackOverFlow

Sure, we can fix it manually, but why “git bash” doesn’t start “ssh-agent” itself when the terminal launched？as we all know we always need it.

Now, lay the question aside firstly, i wanted to let git work elegantly.

Do we execute commands “eval `ssh-agent -s`“ and “ssh-add ~/.ssh/github_rsa” every time when launch a “git bash” terminal?

No, of course not, i can’t bear this trouble, as a engineer who develops software to make life easier.

we can follow the “good” tutorial to let “git bash” start “ssh-agent” itself by appending the commands to the configuration file “$git_installed_directory/etc/bash.bashrc”.

Have we done?

Ha, haven’t, it’s a good resolution, but not the best.

I tested the resolution by opening several “git bash” terminals at the same time, see the picture:

multiple processes

There would be multiple processes if we opened several “git bash” terminals, each process per time.

This was not elegant. I couldn’t bear this resolution too. I wanted to optimize it.

Final

New resolution: check whether the ssh-agent has been started, it’s dependent on the result to execute commands or not.

here is the code:

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#start ssh-agent and add keys
SERVICE='ssh-agent'
if ps -ef|grep -u $SERVICE >/dev/null   #check whether the process started by current user exists 
then
   echo $SERVICE running.
else
   echo $SERVICE not running.
   ssh-agent > ~/.ssh/agent_env  #start the process,and dump the environment variables
   ssh-add ~/.ssh/github_rsa     #just for once,replace 'github_rsa' with your private key
fi
. ~/.ssh/agent_env   #export the environment variables

Add these lines into the end of the configuration file “$git_installed_directory/etc/bash.bashrc”.

Things have been finished, although still had questions here.

  • why do we need to add key each time when “ssh-agent” started?
  • where is it stored? Don’t need to add it every time if keep it stored durably.

Less procedure, launch faster. I will figure out.

——2017-03-06——

continue…

I think the private key identities is stored in memory of ssh-agent process space, so when stop the process, the data would be lost, and don’t need further tuning after trading off.

appendix