Running SSH Agent when starting Git Bash on Windows

P.S: These instructions are in context of a Bash shell opened in Windows 10 Linux Subsystem and doesn't mention about sym-linking SSH keys generated in Windows with Bash on Ubuntu on Windows

1) Update your .bashrc by adding following in it

# Set up ssh-agent
SSH_ENV="$HOME/.ssh/environment"

function start_agent {
    echo "Initializing new SSH agent..."
    touch $SSH_ENV
    chmod 600 "${SSH_ENV}"
    /usr/bin/ssh-agent | sed 's/^echo/#echo/' >> "${SSH_ENV}"
    . "${SSH_ENV}" > /dev/null
    /usr/bin/ssh-add
}

# Source SSH settings, if applicable
if [ -f "${SSH_ENV}" ]; then
    . "${SSH_ENV}" > /dev/null
    kill -0 $SSH_AGENT_PID 2>/dev/null || {
        start_agent
    }
else
    start_agent
fi

2) Then run $ source ~/.bashrc to reload your config.

The above steps have been taken from https://github.com/abergs/ubuntuonwindows#2-start-an-bash-ssh-agent-on-launch

3) Create a SSH config file, if not present. Use following command for creating a new one: .ssh$ touch config

4) Add following to ~/.ssh/config

Host github.com-<YOUR_GITHUB_USERNAME> 
HostName github.com
User git
PreferredAuthentications publickey
IdentityFile ~/.ssh/id_work_gmail # path to your private key
AddKeysToAgent yes


Host csexperimental.abc.com
IdentityFile ~/.ssh/id_work_gmail # path to your private key
AddKeysToAgent yes

<More hosts and github configs can be added in similar manner mentioned above>

5) Add your key to SSH agent using command $ ssh-add ~/.ssh/id_work_gmail and then you should be able to connect to your github account or remote host using ssh. For e.g. in context of above code examples:

$ ssh github.com-<YOUR_GITHUB_USERNAME>

or

$ ssh <USER>@csexperimental.abc.com

This adding of key to the SSH agent should be required to be performed only one-time.

6) Now logout of your Bash session on Windows Linux Subsystem i.e. exit all the Bash consoles again and start a new console again and try to SSH to your Github Host or other host as configured in SSH config file and it should work without needing any extra steps.

Note:

• If you face Bad owner or permissions on ~/.ssh/config then update the permissions using the command chmod 600 ~/.ssh/config. Reference: https://serverfault.com/a/253314/98910

• For the above steps to work you will need OpenSSH v 7.2 and newer. If you have older one you can upgrade it using the steps mentioned at https://stackoverflow.com/a/41555393/936494

• The same details can be found in the gist Windows 10 Linux Subsystem SSH-agent issues

Thanks.

If the goal is to be able to push to a GitHub repo whenever you want to, then in Windows under C:\Users\tiago\.ssh where the keys are stored (at least in my case), create a file named config and add the following in it

Host github.com
    HostName github.com
    User your_user_name
    IdentityFile ~/.ssh/your_file_name

Then simply open Git Bash and you'll be able to push without having to manually start the ssh-agent and adding the key.

2013: In a git bash session, you can add a script to ~/.profile or ~/.bashrc (with ~ being usually set to %USERPROFILE%), in order for said session to launch automatically the ssh-agent.
If the file doesn't exist, just create it.

This is what GitHub describes in "Working with SSH key passphrases".

The "Auto-launching ssh-agent on Git for Windows" section of that article has a robust script that checks if the agent is running or not.
Below is just a snippet, see the GitHub article for the full solution.

# This is just a snippet. See the article above.
if ! agent_is_running; then
    agent_start
    ssh-add
elif ! agent_has_keys; then
    ssh-add
fi

Other Resources:

"Getting ssh-agent to work with git run from windows command shell" has a similar script, but I'd refer to the GitHub article above primarily, which is more robust and up to date.

---

hardsetting adds in the comments (2018):

If you want to enter the passphrase the first time you need it, and not when opening a shell, the cleanest way to me is:

• removing the ssh-add from the .bash_profile, and
• adding "AddKeysToAgent yes" to your .ssh/config file (see "How to make ssh-agent automatically add the key on demand?").

This way you don't even have to remember running ssh-add.

---

And Tao adds in the comments (2022):

It's worth noting why this script makes particular sense in Windows, vs (for example) the more standard linuxey script noted by @JigneshGohel in another answer:

By not relying on the SSH_AGENT_PID at all, this script works across different msys & cygwin environments.
An agent can be started in msys2, and still used in git bash, as the SSH_AUTH_SOCK path can be reached in either environment.
The PID from one environment cannot be queried in the other, so a PID-based approach keeps resetting/creating new ssh-agent processes on each switch.