This utility breaks apart the Dockerfile into multiple, sub-Dockerfiles whenever
an ADD command is found. Each ADD command is run as its own Dockerfile with
its FROM image being the image the previous sub-Dockerfile generated.
A hash of the file being ADDed is generated to create a unique image tag name
in the form of {{ last image id }}-{{ ADD file hash }}.
If an image with this tag already exists, the image does not need to be rebuilt and the existing image's ID is used for the next sub-Dockerfile.
pip install -e git://github.com/baremetal/docker-buildcache@master#egg=docker-buildcache
Consider the following Dockerfile:
FROM ubuntu:quantal
MAINTAINER Roberto Aguilar [email protected]
# Add the Datastax APT repostiory and key
ADD files/etc/apt/sources.list.d/cassandra.list /etc/apt/sources.list.d/cassandra.list
ADD files/var/cache/baremetal/cassandra_repo_key /var/cache/baremetal/cassandra_repo_key
RUN cat /var/cache/baremetal/cassandra_repo_key | apt-key add -
RUN apt-get update
# Install Cassandra
RUN apt-get install -y dsc12 cassandra=1.2.11
Because of the line that adds the APT source, the apt-get command would always have to
be re-run. By building with docker-buildcache subsequent builds look like this:
(dockman)baremetal@baremetal:~/Projects/baremetal/containers/cassandra$ docker-buildcache -t cassandra .
Building image with tag cassandra
Dockerfile content:
FROM ubuntu:quantal
MAINTAINER Roberto Aguilar [email protected]
Building with command: docker build -t cassandra .
Uploading context 93542400 bytes
Step 1 : FROM ubuntu:quantal
---> b750fe79269d
Step 2 : MAINTAINER Roberto Aguilar [email protected]
---> Using cache
---> 6042cc630923
Successfully built 6042cc630923
Image ID: 6042cc630923
ADD filename=files/etc/apt/sources.list.d/cassandra.list, file_hash=75a4df75e0cc
looking for buildcache_tag=buildcache-6042cc630923-75a4df75e0cc
found cache with id 42319f831d2d, skipping build!
ADD filename=files/var/cache/baremetal/cassandra_repo_key, file_hash=ea32a1e7e2b9
looking for buildcache_tag=buildcache-42319f831d2d-ea32a1e7e2b9
found cache with id a684f5110bb0, skipping build!
Building image FROM a684f5110bb0 with tag cassandra
Dockerfile content:
FROM a684f5110bb0
RUN cat /var/cache/baremetal/cassandra_repo_key | apt-key add -
RUN apt-get update
RUN apt-get install -y dsc12 cassandra=1.2.11
Building with command: docker build -t cassandra .
Uploading context 93542400 bytes
Step 1 : FROM a684f5110bb0
---> a684f5110bb0
Step 2 : RUN cat /var/cache/baremetal/cassandra_repo_key | apt-key add -
---> Using cache
---> fd90edb767ce
Step 3 : RUN apt-get update
---> Using cache
---> 4b17f6cb5a3c
Step 4 : RUN apt-get install -y dsc12 cassandra=1.2.11
---> Using cache
---> ac28959e749d
Successfully built ac28959e749d
Image ID: ac28959e749d
On your system you would see images similar to:
(dockman)baremetal@baremetal:~/Projects/baremetal/containers/cassandra$ docker images
[...]
buildcache-42319f831d2d-ea32a1e7e2b9 latest a684f5110bb0 49 minutes ago 2.941 kB (virtual 175.8 MB)
buildcache-6042cc630923-75a4df75e0cc latest 42319f831d2d 49 minutes ago 72 B (virtual 175.8 MB)
Cleaning up the buildcache can be done by running:
docker rmi $(docker images | grep '^buildcache' | awk '{print $3}')