Default base image
Most Galaxy users run their app with the default base image. (For full control over the system libraries available to your app and its precise runtime environment, you can create a custom base image instead.)
A base image is a Docker image. The default base image is stored in the repository meteor/galaxy-app on Docker Hub and is itself based on the repository meteor/ubuntu. The source for these packages can be found in the galaxy-images GitHub repository.
Installed packages
The current Galaxy default base image runs Ubuntu 14.04 LTS and comes with a set of packages pre-installed. Please note that in theory the package versions are not frozen and may be updated at any time. However, in practice, we know that many of our users may implicitly rely on the (increasingly outdated) versions of packages in the default base image. As of now, we plan to continue our implicit policy of never upgrading the Ubuntu packages on the default base image. Users who want newer versions of these packages should create a custom base image instead.
Packages useful as part of the build process:
Packages useful for popular npm packages (primarily image rendering):
- phantomjs
- imagemagick
- graphicsmagick
- libcairo2-dev
- poppler-utils
- libjpeg-dev
- wkhtmltopdf (for HTML to PDF conversion including prerequisites)
- libssl-dev
- xfonts-base
- xfonts-75dpi
- libpoppler-qt4-dev
In addition, the default base image contains several popular versions of Node preinstalled in directories with names like /node-v8.9.3-linux-x64. (Including these versions makes the container build and start process more efficient.) Galaxy uses the official binary distribution of Node from nodejs.org, not the Ubuntu package.
Build time behavior
When you run meteor deploy, your local meteor command-line tool builds your app, bundles it into a tarball, and uploads it to Galaxy. Galaxy then builds a Docker image for your app based on the default base image by running the /app/setup.sh script inside the image. This section describes exactly what the default base image’s /app/setup.sh script does.
First, it extracts your uploaded tarball into the /app directory. The tarball’s contents are all nested under a directory called bundle, so this puts your built app into the /app/bundle directory.
Next, it figures out which version of Node your app was built with. If that version isn’t already part of the image, it downloads and installs it. In either case, it sets the $PATH environment variable to ensure that the correct version of Node is used for the rest of the build process.
Next, it figures out which version of npm your app was built with, and installs that version of npm.
Next, it runs npm install --unsafe-perm inside /app/bundle/programs/server. When building your app, the meteor tool includes the contents of most npm packages in the tarball, but if those packages contain binary code, they may need to be rebuilt for the 64-bit Linux server environment, which is what this command does.
Finally, if the scripts /app/bundle/programs/server/setup.sh or /app/bundle/setup.sh exist, they are executed. (Current versions of Meteor do not make it easy to include these files in your bundle.)
After running all these commands, the Galaxy image builder saves the state of the image to an internal Docker registry.
Run time behavior
When Galaxy runs an app image based on the default base image, it executes a script called /app/run.sh.
This script adds the proper version of Node to $PATH, just like at build time. It also makes the version of Node available in $NODE_VERSION.
If the script /app/bundle/run.sh exists, then this script is executed with bash. (Current versions of Meteor do not make it easy to include this file in your bundle.)
Otherwise, the script runs node $GALAXY_NODE_OPTIONS main.js inside the /app/bundle directory. You can set $GALAXY_NODE_OPTIONS to a flag or space-separated series of flags in your settings.json file if you need fine-grained control over how Node runs your server, such as setting garbage collection flags.