NAME

nitro — a tiny but flexible init system and process supervisior

SYNOPSIS

nitro [dir]

DESCRIPTION

nitro is a service supervisor that can be used as a Unix init system.

Every directory inside dir (by default: /etc/nitro) defines a service.

When used as init, and the argument dir is ‘S’ or ‘single’, nitro looks at the directory /etc/nitro.single instead. This can be used to boot into a special single-user mode.

SERVICE DIRECTORIES

Service directories must have a name shorter than 64 characters and must not contain ‘,’ or newlines in the file name. Service directories cannot be nested.

Service directories can contain the following files:

setup: If it exists, this script is run when starting the service, the service enters state SETUP. When setup exits with status 111, the service enters state FATAL. When setup exits with state 0, the service progresses to state STARTING. Else, setup is restarted after a delay.
run: If it exists, this script should exec into the service. If this file does not exist, the service is a ONESHOT. When the service does not exit for 2 seconds, it enters state UP.
log: If this is a symlink to another service directory, the standard output of the service is connected to the standard input of the target service using a pipe.
finish: After the service has exited, this script is run with two arguments, the exit status of the service and the signal if the service exited due to a signal. Then, the service enters state DOWN.
down: If this file exists, the service is not brought up automatically.
down-signal: If this file exists, the first character of it encodes the signal (see nitroctl(1)) that is sent to the service to bring it down, else SIGTERM.

ENVIRONMENT

NITRO_SOCK: The control socket (by default: /var/run/nitro/nitro.sock) where nitro listens for commands sent by nitroctl(1).

FILES

The following special files are used inside the service directory:

SYS/setup: This script is run very early in boot, before all services are started. It can already start services using nitroctl(1).
SYS/finish: When system shutdown is requested, this script is run. When it exits, the remaining services are brought down.
SYS/reincarnate: If this script exists, nitro execs into it instead of rebooting or shutting down.
SYS/final: This script is run after all services are stopped. When it exits, the root file system is remounted read-only and the system shuts down/reboots.

EXIT STATUS

nitro tries hard not to exit, being used as pid 1.

AUTHORS

Leah Neukirchen <leah@vuxu.org>