Customized bootstrapping

[achimnol]

Users would want to install their own packages via pip.
We could use a simple config file which describes the package list to install on startup of kernel session.

• Define a simple format to list up dependencies, maybe as YAML
  • requirements.txt format is perfect for Python, including custom index support. We could allow users to specify it as a whole using YAML content block.
  • System packages (apt-get) or their whilte-listed aliases (e.g., "build-tools" installs "build-essential" and "python-dev" in Python containers while "build-essential" and "php7-dev" in PHP containers)
  • Backend.AI-specific options such as various CUDA versions
• Implement the installation process on startup
• Provide a local .pip cache for commonly used packages (e.g., numpy) as Docker volumes like Travis CI
• Storage information to store the generated artifacts (e.g., virtual folder ID, external S3 bucket with credentials) — idea by @serialx
• Provide a way to show the config applied to the kernel session (API New/Update: Per-session configuration APIs backend.ai-manager#50)