How about manage system dependencies when using azk? - ruby-on-rails-4

Question

I'm using azk and my system depends on extra packages. I'd be able to install them using (since I'm using an Ubuntu-based image):
apt-get -yq update && apt-get install -y libqtwebkit-dev qt4-qmake
Can I add this steps to provision? In the Azkfile.js, it would look like:
// ...
provision: [
"apt-get -yq update",
"apt-get install -y libqtwebkit-dev qt4-qmake",
"bundle install --path /azk/bundler",
"bundle exec rake db:create",
"bundle exec rake db:migrate",
]
Or it's better to create a new Docker image?

Answer 1

Provision steps are run in a separated container, so all the data generated inside of it is lost after the provision step, unless you persist them. That's why you probably have bundle folders as persistent folders.
Since that, you should use a Dockerfile in this case. It'll look like this:
FROM azukiapp/ruby:2.2.2 # or the image you were using previously
RUN apt-get -yq update && \
apt-get install -y libqtwebkit-dev qt4-qmake && \
apt-get clean -qq && \
rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* # Keeping the image as small as possible
After that, you should edit your Azkfile.js and replace the image property of your main system to use the created Dockerfile (you can check azk docs here):
image: { dockerfile: './PATH_TO_DOCKERFILE' },
Finally, when you run azk start, azk will build this Dockerfile and use it with all your dependencies installed.
Tip: If you want to force azk to rebuild your Dockerfile, just pass -B flag to azk start.

Answer 2

As it looks like you're using a Debian-based Linux distribution, you could create (https://wiki.debian.org/Packaging) your own Debian virtual package (https://www.debian.org/doc/manuals/debian-faq/ch-pkg_basics.en.html#s-virtual) that lists all the packages it depends on. If you just do that one thing, you can dpkg -i (or apt-get install if you host a custom debian repository yourself) your custom package and it will install all the dependencies you need via apt.
You can then move on to learning about postinst and prerm scripts in Debian packages (https://www.debian.org/doc/manuals/debian-faq/ch-pkg_basics.en.html#s-maintscripts). This will allow you to run commands like bundle and gem as the last step of the package installation and the first step of package removal.
There are a few advantages to doing it this way:
1. If you host a package repository somewhere you can use a pull method of dependency installation in a dynamic scaling environment by simply having the host apt-get update && apt-get install custom-dependencies-diego
2. Versioning your dependency list - Using dpkg -l you can tell what version everything is on a given host, including the version of your dependency virtual package.
3. With prerm scripts, you can ensure that removing your virtual package will also have the effect of removing the changes your installation scripts made so you can get a host back to a "clean" state".
The disadvantage of doing it this way is that it's debian/apt specific. If you wanted to deploy to Slack or RHEL you'd have to change things a bit. Changing to a new distro wouldn't be particularly hard, but it's definitely not as portable as using Bash, for example.