Nitro: a tiny but flexible init system and process supervisor

The most unlikely subsystem of contention is definitely the init system used by Linux, with most popular distributions opting for systemd, while a vocal minority prefers to use something else. Neither of these two groups are wrong or right, as we live in a free world and different people have different needs and desires. Personally, I don’t think there’s a more utterly pointless and meaningless debate than this, and people who make the init system they use their entire personality more often than not come across as really, really sad.

It’s a tool; use the one you like and move on with life.

A brand new init system was recently released by Leah Neukirchen, who among a ton of other things, contributes to Void Linux. It’s called nitro, and it’s a “tiny process supervisor that also can be used as pid 1 on Linux”, and it also can be used on FreeBSD supervised by FreeBSD’s init. There’s some overlap with runit here, so Neukirchen published a blog post detailing the differences between the two, which should help in getting a better understanding of what makes nitro stand apart. While both use a directory of services managed by small scripts, nitro seems to opt for a more contained, monolithic approach, as it keeps everything in a single process.

On top of that, Nitro contains some new features runit doesn’t have. The focus seems to be on integrating a few capabilities that on runit require hacks, but on nitro are just built-in, like “support for one-shot ‘services’, i.e. running scripts on up/down without a process to supervise (e.g. persist audio volume, keep RNG state)”, running service directories multiple times, and more. Nitro also maintains its runtime state in RAM and provides an IPC service to query it, meaning it can be run on read-only filesystems without special configuration.

There’s a lot more information in Neukirchen’s blog post, including a look at some of the current limitations of Nitro. I highly suggest reading it, and perhaps we will see nitro as another valid alternative to the popular systemd.