Windows subsystem for linux - share ssh-agent?

Question

I am running Ubuntu 16.04 within a Windows Subsystem for Linux (WSL) shell on Windows 10. From within a terminal I can start ssh-agent and use it many times over the life of that terminal. I can see the ssh-agent running from ps, and also from the Windows 10 task manager.

However, if I start a 2nd WSL bash terminal from the start menu, it is unaware of the ssh-agent. Oddly, if I start a 2nd terminal from the windows command line, it works. A possible workaround would be to open new bash windows from the existing one, but I don't know how to do that either.

Is there any solution to this?

Answer 1

You can modify your .bashrc to find an existing running ssh-agent.

I use something based on the gist

# ssh-agent configuration
if [ -z "$(pgrep ssh-agent)" ]; then
    rm -rf /tmp/ssh-*
    eval $(ssh-agent -s) > /dev/null
else
    export SSH_AGENT_PID=$(pgrep ssh-agent)
    export SSH_AUTH_SOCK=$(find /tmp/ssh-* -name agent.*)
fi

# optional... potentially annoying
#if [ "$(ssh-add -l)" == "The agent has no identities." ]; then
#    ssh-add
#fi

Answer 2

Perhaps not: it sounds as if ssh-agent is being run in the usual way, where it is the parent process of your shell. That other window has its own hierarchy of process parent/child which doesn't tie into the window that you are using.

One way to work with this feature of ssh-agent is to run screen (or tmux) within the window where you have started the agent. Those screen/tmux windows are also children of the ssh-agent process, and can talk to it without problems.

Answer 3

I prefer this script that use ssh-add to find if your keys has already been added

ssh-add -l &>/dev/null
if [ "$?" == 2 ]; then
  test -r ~/.ssh-agent && \
    eval "$(<~/.ssh-agent)" >/dev/null

  ssh-add -l &>/dev/null
  if [ "$?" == 2 ]; then
    (umask 066; ssh-agent > ~/.ssh-agent)
    eval "$(<~/.ssh-agent)" >/dev/null
    ssh-add
  fi
fi

You can read more about it on: http://rabexc.org/posts/pitfalls-of-ssh-agents

Answer 4

There is now. Install the latest version of OpenSSH for windows, and then get the ssh-agent-wsl helper. Follow the instructions, and you'll very easily get a working way to share credentials across WSL and Windows! It works like a charm!

Answer 5

One possible solution to your problem is the work-around / hack that I am using at the time of writing. However, I am also searching for another easy solution. I am using Windows 10 Pro Version 1903 Build 18362.418 and Ubuntu 18.04 in WSL.

I noticed that when ever I start 'ssh-agent' in WSL, a process of 'ssh-agent' is started in Windows 10.

The work-around / hack I am using is that I start 'ssh-agent' is WSL by using ssh-agent, It gives me some output like

SSH_AUTH_SOCK=/tmp/ssh-4T3ZkVnWhIA7/agent.19; export SSH_AUTH_SOCK; SSH_AGENT_PID=20; export SSH_AGENT_PID;

I copy these commands and paste / execute them in WSL to connect with 'ssh-agent' and then save these commands in a text file in windows 10.

I add keys to 'ssh-agent' in WSL as usual.

Whenever I open a new WSL session, I simple paste / execute these saved commands in New WSL session terminal and the new WSL session connects to already existing 'ssh-agent' process and I don't have to start a new 'ssh-agent' and add keys again.

EDIT 1: Recently I used another work-around / hack. Instead of coping the output generated by ssh-agent and then pasting the copied content to New WSL session terminal to use already started 'ssh agent'.

I performed these commands in first WSL session terminal.

ssh-agent > ssh_env source ssh_env

and then if I needed New WSL session terminal, I just started it and used

source ssh_env

to connect with already started 'ssh agent'. This just reduced the steps of coping, saving and later using the output generated by ssh-agent that I had mentioned before.

Hope this helps.

PS. I don't launch WSL from Windows 10 Command Prompt using wsl.exe.

I usually open WSL form 'Start Menu'.

Answer 6

There is an even easier solution to that, automate the process by adding:

source <(ssh-agent)

to your .bashrc, and each time you login you will get the env variables automatically.