Summary

In Bitbucket Pipelines, there are some scenarios where it's required to run ssh commands inside a Dockerfile. 

Cause

The Dockerfile within the Pipeline by default doesn't have access to the SSH key variables configured in Bitbucket Pipelines. 

Solution

The key has to be added as an environment variable and explicitly passed as an argument to the Dockerfile.

• Currently, Bitbucket Pipelines do not support line breaks in environment variables, so base-64 encode the private key by running:
  • Linux:

$ base64 -w 0 < my_ssh_key

• • macOS: 

$ base64 < my_ssh_key

• Then, use the SSH key variable in the Dockerfile:

FROM atlassian/default-image:3

ARG SSH_PRIVATE_KEY
RUN mkdir -p /root/.ssh/ && chmod 700 /root/.ssh 
RUN (umask  077 ; echo $SSH_PRIVATE_KEY | base64 --decode > ~/.ssh/id_rsa)
RUN touch ~/.ssh/known_hosts
RUN ssh-keyscan -T 60 bitbucket.org >> ~/.ssh/known_hosts

• Pass the SSH key variable using the "--build-arg" argument in the docker build command:

docker build --build-arg "SSH_PRIVATE_KEY=$SSH_PRIVATE_KEY" .