Build LXC containers using Dockerfile like DSL
Nut is a minimal golang based CLI for building LXC containers. It allows user create containers using Dockerfile like syntax, archiving and publishing them in s3. Nut is intended to be used in CI/CD infrastructure to build & publish container images as artifacts. Nut complements the lxc cli tools, as well as provide golang based public API for extensions.
All features of nut are implemented as set of sub commands
nut --help
usage: nut [--version] [--help] <command> [<args>]
Available commands are:
archive Create tarball images of existing container
build Build container from Dockerfile
fetch Create container from images stored in s3
multi Build multi container environment from docker compose specification
publish Publish tarball images of existing container in s3
restore Create container from tarball image
run Run command/entrypoint inside a container
- build, restore and fetch is used create containers. From dockerfile like syntax or images stored in s3 or localdisk
- multi is used to setup a group of containers from docker-compose like specification.
- archive and publish allows creating and publishing container images in s3
Nut stores container metadata as mainfest.yml file inside the container directory, right next to rootfs directory. Manifest data stores all labels, maintainers, exposed ports and entry point details. Labels that starts with "nut_artifact" are treated differently, their values are considered as build artifacts and fetched from inside the container to current directory. Following is an example of building ruby 2.2.3 debian packages for trusty using nut
Example:
- Dockerfile
FROM trusty
MAINTAINER ranjib@pagerduty.com
RUN apt-get update -y
RUN apt-get install -y build-essential curl git-core libcurl4-openssl-dev libffi-dev libreadline-dev libsqlite3-dev libssl-dev libtool libxml2-dev libxslt1-dev libyaml-dev openssh-server python-software-properties sqlite3 wget zlib1g-dev
RUN mkdir -p /opt/ruby
RUN git clone https://github.com/sstephenson/ruby-build.git /opt/ruby-build
RUN /opt/ruby-build/bin/ruby-build 2.2.3 /opt/ruby/2.2.3
RUN /opt/ruby/2.2.3/bin/gem install bundler fpm --no-ri --no-rdoc
RUN /opt/ruby/2.2.3/bin/fpm -s dir -t deb -n ruby-2.2.3 -v 1.0.0 /opt/ruby/2.2.3
LABEL nut_artifact_ruby=/root/ruby-2.2.3_1.0.0_amd64.deb
And then nut can be invoked as:
nut build -ephemeral
Upon invocation nut will clone a new container from trusty
, execute the RUN statement, which in turn will build ruby debian package, and then copy theresulting debian from /root/ruby-2.2.3_1.0.0_amd64.deb to current directory.
Since vanilla LXC is not aware of image repositories, all containers are created from cloning existing container(s). A trusty (ubuntu 14.04) container can be created as
lxc-create -n trusty -t download -- -d ubuntu -a amd64 -r trusty
This in turn, can be used inside a Dockerfile DSL via the FROM
instruction.
Nut converts the image name from org/repo:version
to 'org-repo_version' as the container
from which the new container will be built.
For example FROM pagerduty/ruby:2.2.3
will instruct Nut to create a container by cloning
an existing container named pagerduty-ruby_2.2.3
.
We use vagrant for development purpose. Following will setup a development vagrant instance as well as kick a test job.
vagrant up
vagrant reload
vagrant ssh -c "nut build -specfile gopath/src/github.com/PagerDuty/nut/Dockerfile -ephemeral"