I want to pull code from Github into my Docker image while building. I have a deploy key generated from the repository, but it seems to me the ssh-agent is not working on my Docker image.
What I did (my Dockerfile):
FROM python:2.7-stretch
ADD ./id_rsa /root/.ssh/id_rsa
RUN eval "$(ssh-agent -s)"
RUN ssh-add -K /root/.ssh/id_rsa
Output:
Step 12/22 : RUN eval "$(ssh-agent -s)"
---> Running in f9ad80981cee
Agent pid 6
Removing intermediate container f9ad80981cee
---> d773f7ce5917
Step 13/22 : RUN ssh-add -K /root/.ssh/id_rsa
---> Running in 95efeed6a7ad
Could not open a connection to your authentication agent.
The command '/bin/sh -c ssh-add -K /root/.ssh/id_rsa' returned a non-zero code: 2
As you can see, ssh-agent is started, but keys are not adding in it.
If I skip the ssh-add step then my git pull fails later because of privileges, which is failing as expected as no authentication happened.
Actually you don't need to copy your private key to your container (and you better not do it).
All you need is the ssh-agent installed and launched on both: your host and your docker container then all you need to do is to mount the ssh-aget's socket file:
If you are using docker-compose:
environment:
- "SSH_AUTH_SOCK=/tmp/ssh-agent"
volumes:
- $SSH_AUTH_SOCK:/tmp/ssh-agent
With docker:
docker run -v $SSH_AUTH_SOCK:/tmp/ssh-agent 8be57bbc9561 sleep 1000000 # 8be57bbc9561 is an id of the image
docker exec -it -e SSH_AUTH_SOCK=/tmp/ssh-agent 5b6f4a8f8661 /bin/ash # 5b6f4a8f8661 is an id of the container
P.S
As of your case, I think the problem can be related to the export command which is normally evaled from the code from the output of the ssh-agent.
It should provide you two variables: SSH_AUTH_SOCK and SSH_AGENT_PID. But the export won't persist across images.
You've used RUN two times: first for launching the ssh-agent and exporting variables and then for adding a key. And each Dockerfile directive will generate an intermediate container (and export won't persist across them).
If you still want to use it this way (which I stronly recommend to avoid), you can try to bind both command in a single RUN:
RUN eval "$(ssh-agent -s)" && ssh-add /root/.ssh/id_rsa
I've written a short post based on my answer above.