vinit

vinit

vinit is the experimental Vinyl Linux init system. It borrows heavily from many init systems, is written in go, and is distributed as static binary with no external dependencies.

It:

1. Uses toml files to configure both the init process, and individual services
2. Supports 'groups' of services, with the ability to override groups for customisation of boot order
3. Supports simple SysV style ordering by prefixing services with numbers, for example, 00-foo, 10-bar, etc.
4. Uses directories and symlinks to provide entrypoints, working directories, and logs in a way inspired massively by s6
5. Exposes operations over a gRPC powered unix socket, allowing for better programmatic control of a system

It specifically doesn't:

1. Require complex boot scripts- a service expects a file called bin, which usually is just a symlink
2. Require thought around boot order- I don't care about complicated boot dependency trees; use a group/ alphabetical order to order things properly
3. Do anything particularly fancy- it just supervises some services, restarting anything that needs restarting

Installation

vinit can be installed/ upgraded with vin:

vin install vinit

Or simply downloaded from https://github.com/vinyl-linux/vinit/releases. The script install.sh in the latest version of vinit here can be run from within the latest release to install vinit to a system.

If installing manually, make sure you have some vinit services configured or nothing much will happen on boot (you'll get nothing but a terminal). Sample scripts may be found at https://github.com/jspc/vinit-bootscripts.

vinit Services

Services are usually installed at /etc/vinit/services - certainly this is the default location. Other directories can be used instead, simply by setting the environment variable SVC_DIR before starting vinit.

Each service is contained in its own directory. The directory name is used as the service name, though an optional numeric prefix may be used to affect the order in which services start.

For instance: the directory my-application will contain the service my-application. Similarly, the directory 10-my-application also contains the service my-application. Because services are read alphabetically, using the numeric prefix will allow for rudimentary boot ordering.

A service directory looks like:

10-my-application
├  .config.toml
├  bin
├  environment
├  environment_overrides
├  logs
│   ├ stderr
│   └ stdout
└  wd

Where:

1. .config.toml is the service configuration, including arguments to pass to bin, setuid configuration, and grouping information. This is described in depth below.
2. bin is the script/ binary/ application to run (which is usually a symlink; see: 20-dropbear/bin, which points to /usr/sbin/dropbear)
3. environment is a file containing KEY=value pairs, and is used to set the environment in which bin runs
4. environment_overrides is a file much the same as environment, but with system specific vars; in vinit we assume that environment is owned by the package maintainer, and as such can be clobbered by upgrades, whereas environment_overrides (which is loaded after environment and, as such, overrides vars in that file) is owned by the user and can be used to tune things better
5. logs is a directory containing a file for both stdout and stderr (this directory/ these files will be created if they don't exist, with each file being appended to- vinit doesn't handle log rotation)
6. wd is a directory (which is also often a symlink; see 99-vind/wd, which points to /etc/vinyl

In essence, then, when the service my-application is started vinit will start 10-my-application/bin with the args from 10-my-application/.config.toml, from within the directory 10-my-application/wd, and with logs going to 10-application/logs/[stderr,stdout].

.config.toml file

A fully featured example, with optional values listed, looks like:

type = "service"           # The different types are: "service", "oneoff", "cron"
reload_signal = "SIGHUP"   # The signal to send to a process during reload- such as to reload config. Defaults to SIGHUP

[user]
user = "nobody"            # Default: root
group = "nobody"           # Default: root

[grouping]
name = "none"              # Required, but setting to an unknown group will stop it autobooting

[command]
args = "-v"                # Optional; if empty then ./bin is started with no args
ignore_output = false      # Defaults to false; governs whether stdout/stderr is ignoresd

Additionally, configuration for types cron and oneoff must contain (respectively):

[oneoff]
valid_exit_codes = [0]    # Exit statuses for this job that governs whether a job failed successfully


[cron]
schedule = "@daily"       # Any of the standard crontab (* * * * *) style schedule, plus the less standard (but common) things like @daily, @hourly, etc.

Licence

BSD 3-Clause License

Copyright (c) 2022, Vinyl Linux All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.