Docker Load key "/root/.ssh/id_rsa": invalid format

For reference only.

I created a private key file key.id_rsa manaully and pasted content to it. But when I used it to clone git repository:

$ git clone my_repo
Cloning into 'my_repo'...
Load key "/path/to/key.id_rsa": invalid format

The key's content is definitely correct. So then I tried compare my key with the other generated key by ssh-keygen, it's truely invalid format.

Just no end of new line in my key.

After added new line to the end of key, all worked delightful~ What a suprise!

[Update]: Remember use \n instead of \r\n even on windows.

If the key is "invalid format", try and regenerate it with the old PEM format.

ssh-keygen -m PEM -t rsa -P "" 

Make sure to add the public key to your GitHub account for proper authentication.

The OP Shammir adds in the comments:

I think the issue is that nothing is being copied from host machine to docker image during build.

In "docker build --build-arg SSH_PRIVATE_KEY="$(cat ~/.ssh/id_rsa)" returning empty", Shammir uses dockito/vault to manage the private key, but also configure it to "AddKeysToAgent": that is not needed if the private key is not passphrase protected (as in my command above)

Another possible gotcha is if you're using a Makefile to run the docker build command. In that case the command in the Makefile would look something like:

docker-build:
    docker build --build-arg SSH_PRIVATE_KEY="$(shell cat ~/.ssh/id_rsa)"

Make unfortunately replaces newlines with spaces (make shell)

This means that the ssh key which is written into the container has a different format, yielding the error above.

I was unable to find a way to retain the newlines in the Makefile command, so I resorted to a workaround of copying the .ssh directory into the docker build context, copying the files through the Dockerfile, then removing them afterwards.