Mix.install doesn't honour `GIT_SSH_COMMAND`

rlipscombe

When I use Mix.install with a git dependency, using git@github.com:... how do I change the SSH identity used?

I’ve got two Github accounts – work and personal, and usually I’d specify GIT_SSH_COMMAND=ssh -i path/to/private_key -o IdentitiesOnly=yes.

This works fine when running, say, iex and Mix.install in my terminal. When I try the same in Livebook, I get the following error:

git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

I’ve tried editing .livebookdesktop.sh – and the env var is set properly according to System.get_env; didn’t work.

I’ve tried using system_env: %{"GIT_SSH_COMMAND" => "ssh -i ... in Mix.install; didn’t work.

How do I get Mix.install to use alternate SSH identities inside Livebook?

9 comments

/livebook #ssh #git

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2026-11-04 17:26:46 UTC

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dimitarvp

Why is using the https://... links not an option, by the way? You can just export the GITHUB_TOKEN env var and it should just work. At least it does for me locally in the OS, locally in a Docker container, and in GitHub’s workers (with the .insteadOf git setting on top).

Post #1

rlipscombe

I don’t want the extra step involved in managing a personal access token.

Post #2

dimitarvp

Is that adding more friction than providing the extra step of a private key and the command to use it? Your call, seems to me the token would be a touch easier.

Post #3

rlipscombe

I’ve already got the extra private key, so: yes.

Moreover, in order to apply the .insteadOf option, I need a configuration file. And, because I’m keeping my personal and work configurations separate, it’s a separate configuration file.

And, if I could persuade Mix.install to use a separate configuration file, I wouldn’t need the env var – because the configuration file already specifies core.sshCommand, but that doesn’t seem to do anything here either.

Post #4

josevalim

Creator of Elixir

We don’t do anything special here, so my only suspicion is that the environment variable is not making its way to git. You could try creating a simple git script, put it on top of your $PATH, and call env to inspect all of the environment variables. If the GIT_SSH_COMMAND you set at .livebookdesktop.sh is missing, that would explain it.

Post #5

rlipscombe

I did this. The GIT_SSH_COMMAND environment variable is present, but seems to be ignored by the real git command.

Ah! I wonder whether it’s because it can’t talk to the running ssh agent, so it can’t unlock the private key…?

Post #6

rlipscombe

Yes, probably this. System.get_env() includes "SSH_AUTH_SOCK" => "/private/tmp/com.apple.launchd.BlahBlah/Listeners".

This is not the SSH_AUTH_SOCK that my shell’s using – SSH_AUTH_SOCK=/var/folders/bunch/of/letters/and/numbers/agent.1234

I’ve got two ssh-agent processes running, and Livebook’s talking to the one that doesn’t have my keys loaded.

I wonder how to get oh-my-zsh to talk to the launchd-started one, instead of starting a new one…? That’s a problem for a different forum, however.

Thanks for the pointers.

Post #7

rlipscombe

Summary:

Mix.install uses the git command normally, so environment variables and configuration settings should just work.
If you’re using SSH, it will need access to your private keys. This requires access to a running ssh-agent with those keys.
If you’re managing your ssh-agent with a login script, etc., you’ve probably got more than one ssh-agent running.
On macOS (at least), Livebook will be talking to the launchd-started ssh-agent.
This one won’t have your keys.
Sad times.