Clone private git repo with dockerfile

I have copied this code from what seems to be various working dockerfiles around, here is mine:

FROM ubuntu

MAINTAINER Luke Crooks "luke@pumalo.org"

# Update aptitude with new repo
RUN apt-get update

# Install software 
RUN apt-get install -y git python-virtualenv

# Make ssh dir
RUN mkdir /root/.ssh/

# Copy over private key, and set permissions
ADD id_rsa /root/.ssh/id_rsa
RUN chmod 700 /root/.ssh/id_rsa
RUN chown -R root:root /root/.ssh

# Create known_hosts
RUN touch /root/.ssh/known_hosts

# Remove host checking
RUN echo "Host bitbucket.org\n\tStrictHostKeyChecking no\n" >> /root/.ssh/config

# Clone the conf files into the docker container
RUN git clone git@bitbucket.org:Pumalo/docker-conf.git /home/docker-conf

This gives me the error

Step 10 : RUN git clone git@bitbucket.org:Pumalo/docker-conf.git /home/docker-conf
 ---> Running in 0d244d812a54
Cloning into '/home/docker-conf'...
Warning: Permanently added 'bitbucket.org,131.103.20.167' (RSA) to the list of known hosts.
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
2014/04/30 16:07:28 The command [/bin/sh -c git clone git@bitbucket.org:Pumalo/docker-conf.git /home/docker-conf] returned a non-zero code: 128

This is my first time using dockerfiles, but from what I have read (and taken from working configs) I cannot see why this doesn’t work.

My id_rsa is in the same folder as my dockerfile and is a copy of my local key which can clone this repo no problem.

Edit:

In my dockerfile I can add:

RUN cat /root/.ssh/id_rsa

And it prints out the correct key, so I know its being copied correctly.

I have also tried to do as noah advised and ran:

RUN echo "Host bitbucket.org\n\tIdentityFile /root/.ssh/id_rsa\n\tStrictHostKeyChecking no" >> /etc/ssh/ssh_config

This sadly also doesn’t work.