Appendix B: What Is a Package Manager?

If Helm is "the package manager for Kubernetes", we need to have a common explanation of what we mean by "package manager".

Helm's notion of package management is informed by operating system package managers such as:

It is important to not overzealously compare Helm to programming language library package managers, as such systems have a fundamentally different goal.

Package managers such as Apt, Homebrew, and RPM provide the following services:

They define a package format
They define a package repository architecture
They define a security model (signing, verification, etc)
They specify a programming langugage (or languages) to be used for management logic (e.g. shell scripts, Ruby)
They manage the installation, upgrade, and deletion of a package
They provide dependency resolution features and version management
They expose configuration options that the user may override
They start services (e.g. when installing a database, the database is started) and often provide tooling for administrators to manage those services (e.g. systemd/upstart/sysV init scripts)
They provide tools to search, list, and discover packages
They implement (or make it easy to implement) environment-specific (os, processor, distro) optimizations
They provide an opinion as to how to best construct and maintain packages
They surface documentation (typically via output during installation)

Package managers tend to involve all of these because it is important in package management to keep external dependencies to a minimum.

Consequently, if Helm is to fit into such a paradigm, it is natural that Helm will provide at least most, if not all of these.

Helm is not a configuration management tool (such as Chef or Puppet). Helm does provide certain features of such systems, though. Helm's templating and configuration model is a common feature of configuration managers (and also of package managers).