dgoffredo/minit

a make-based init system

Minit

Minit is a make-based init system for services. It's simple and doesn't do much.

The name rhymes with "in it."

Why

I worked with a homebrewed init system at Bloomberg that was written mostly in Perl, and I always wondered whether it could be simplified by leveraging make for dependency tracking and parallel job execution.

What

minit is a script and a set of conventions that allow a system of interdependent services (processes) to be started and stopped cleanly.

It is similar to, but not an implementation of, the Linux Standard Base's init system.

minit is mostly a Makefile with start and stop targets, together with shell script glue for deducing make rules and recipes from a prescribed directory structure of configurations.

How

minit start starts all services. minit stop stops all services.

A service is a directory containing two files:

etc/minit/services/
                   weatherd/
                            init
                            deps

weatherd is the name of the service (maybe a daemon that provides weather forecasts).

weatherd/init is an executable that accepts a single command line argument: either "start" or "stop".

• init start starts the service, or does nothing if it's already started.
• init stop stops the service, or does nothing if it's already stopped.
• In either case, the script exits with a zero status on success, or a nonzero status if an error occurs.

weatherd/deps is a file containing the names of all of the services on which weatherd depends, separated by whitespace (including newlines). For example, weatherd/deps might look like this:

routerd
redis
procmgr
locationd

or, equivalently, like this:

routerd redis procmgr locationd

When weatherd/init start is executed, its output is written to the two files:

var/log/minit/$(date --utc +%s.%N).start/weather/{stdout,stderr}

The directory $(date --utc +%s.%N) is shared by all services for that particular invocation of minit start (i.e. the name of the directory is calculated only once per minit invocation). Similarly for minit stop.

Install

make install will copy files into the directory tree rooted at PREFIX. If the PREFIX variable is not set, then it defaults to /usr/local. You might need to run the command with sudo if you don't have write permissions under PREFIX.

make uninstall removes the previously installed files and directories, including any logs previously produced by minit.

More

Minit is a toy that doesn't do any of the following important things:

• runlevels
• timeouts
• different flavors of dependencies (e.g. Should-Stop, Default-Start)
• sensible error reporting (make will just fart at you)

It would not suffice at all as an init system for a real Linux distribution. However, if you have a subsystem of interrelated processes, such as a bunch of GRPC services, database proxies, etc., then minit might be a viable place to start.