Running Docker pull command in Dockerfile

Question

I am new to Docker and trying some things. Now I want to create a Dockerfile, which build automatically the Oracle DB image.

############################################################
# Dockerfile to build MongoDB container images
# Based on Ubuntu
############################################################

# Set the base image to Ubuntu
FROM ubuntu

# File Author / Maintainer
MAINTAINER Example McAuthor

# Update the repository sources list
RUN apt-get update

################## BEGIN INSTALLATION #####################
CMD docker pull alexeiled/docker-oracle-xe-11g

My problem is the docker pull command.
When I try to use the RUN command, the docker daemon say, that he can't find 'docker'. Then I use the CMD command, and it works, but is that correct? Maybe you can show me alternative ways.

Answer 1

You should not pull from a Dockerfile.

You simply can start your Dockerfile with:

FROM docker-oracle-xe-11g

And add in it any Oracle config file which you would need in your own Oracle image.
The docker-oracle-xe-11g Dockerfile is already based on ubuntu.

FROM ubuntu:14.04.1