Use SSH key of host during Singularity build

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When building a singularity image from a definition file, is there a portable way to make a SSH key of the host system available during the build?

To give some context:

I have a definition file where in the %post section I'm cloning a private git repository using SSH, i.e.:

git clone git@github.com:luator/private_repo.git

This fails because the SSH keys of the host system are not available in the container during the build.

I could probably copy the key in the container and delete it from there at the end of the build process. However, for this, I would need to hard-code the path to the key in the definition file, which is bad when using the same definition file on another machine where the path is different. Is there a more portable way of making the git clone work during the build?

singularity-container ssh-keys git
1 Answers

You can try using docker Buildkit, export DOCKER_BUILDKIT=1 to enable this feature:

And afterwards just generate your ssh keys (ssh-keygen and be sure that your public key - id_rsa.pub file content is in your github/gitlab/bitbucket)

Simple usage in a Dockerfile:

# use you base image
FROM centos AS build
  
RUM yum install -y git

RUN mkdir -m 700 /root/.ssh; \
    touch -m 600 /root/.ssh/known_hosts; \
    ssh-keyscan github.com > /root/.ssh/known_hosts

# update with tour repo
RUN --mount=type=ssh,id=github git clone git@github.com:<USER>/<REPO>.git

And then build the image RUN --mount=type=ssh,id=github git clone git@github.com:<USER>/<REPO>.git

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