Ansible from ppa won't install python-related packages

Question

When I build my dockerfile, which does the following:

FROM debian:jessie
...
RUN echo "deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main" > /etc/apt/sources.list \
    && apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 93C4A3FD7BB9C367 \
    && apt-get update \
    && apt-get install ansible

I get:

The following packages have unmet dependencies:
 ansible : Depends: python-jinja2 but it is not installable
           Depends: python but it is not installable
           Depends: python-yaml but it is not installable
           Depends: python-paramiko but it is not installable
           Depends: python-httplib2 but it is not installable
           Depends: python-six but it is not installable
           Depends: python-crypto (>= 2.6) but it is not installable
           Depends: python-setuptools but it is not installable
           Depends: sshpass but it is not installable
           Depends: python-pkg-resources but it is not installable

Shouldn't the process of installing ansible already install these packages? I'm kinda noob into this, but as I know, one package can list dependencies for other packages, so why these aren't installing automatically? Shouldn't debian also come with python at least?

I've put them into the apt-get script and it worket, but shouldn't it be automatic? What if a new ansible package in the ppa requires more packages? It'd break my dockerfile

Solution 1

Instead of overriding the /etc/apt/sources.list file using > you can append the text using >>.

So it will be something similar to the following.

RUN echo "deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main" >> /etc/apt/sources.list \
&& apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 93C4A3FD7BB9C367 \
&& apt-get update \
&& apt-get install -y ansible

Solution 2

Try adding the -f option to apt-get install, which attempts to fix broken dependencies. Prior to running apt-get update you may also want to run apt-get clean to clear the local apt repo. These worked for my Packer build that uses the Ansible provisioner.

Your code would become:

RUN echo "deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main" > /etc/apt/sources.list \
&& apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 93C4A3FD7BB9C367 \
&& apt-get autoclean \
&& apt-get update \
&& apt-get install -f ansible

For additional details I recommend this excellent answer to the broader question, "How do I resolve unmet dependencies after adding a PPA?"