Run our official Docker images, prepackaged with varied language combinations. To fine-tune Unit to your goals, download the sources, install the toolchain, and build a custom binary from scratch; just make sure you know what you’re doing. OpenRC is a dependency-based init system that maintains compatibility with the system provided init program, normally located in /sbin/init.It is Gentoo's native init system, although other systems are available. OpenRC is a dependency-based init system that maintains compatibility with the system provided init program, normally located in /sbin/init.It is Gentoo's native init system, although other systems are available.

1. Gentoo Docker Systemd
2. Docker Gentoo Portage

OpenRC is a dependency-based init system that maintains compatibility with the system provided init program, normally located in /sbin/init. It is Gentoo's native init system, although other systems are available.

OpenRC does not function as a replacement for the /sbin/init file by default and is 100% compatible with Gentoo init scripts. This means a solution can be found to run the dozens of daemons in the Gentoo ebuild repository.

OpenRC is not designed to be exclusively used by Gentoo Linux and is deployed other Linux distributions and BSD systems.

Features

OpenRC provides a number of features touted as innovative by recent init systems like systemd or upstart (wikipedia), such as:

• cgroups support.
• Process supervision.
• Parallel startup of services.
• Hardware initiated initscripts.

It does this without requiring large layout changes to accommodate radically different designs and dependencies.

OpenRC Busybox integration

Busybox can be used to replace most of the userspace utilities needed by OpenRC (init, shell, awk, and other POSIX tools), by using a complete Busybox as shell for OpenRC all the calls that normally would cause a fork/exec would be spared, improving the overall speed. This process is not yet streamlined.

Please note that there are currently many Busybox applets that are incompatible with OpenRC. See bug #529086 for details.

Replacing init

In order to set a specific runlevel from the bootloader the variable softlevel= should be used.

busybox

The SysV-init /etc/inittab file provided by Gentoo is not compatible with the Busybox init.

openrc-init

OpenRC has its own init system called openrc-init. See OpenRC/openrc-init for details.

Daemon supervision

OpenRC has its own process supervisor. See OpenRC/supervise-daemon for details.
Alternatively Skarnet's S6 is also supported by OpenRC. See S6 for details.

Busybox specific init.d files

TODO: busybox provides a number of applets that could be used to replace third party software like acpid or dhcp/dhcpcd.

Replacing udev with mdev

See mdev.

Replacing udev with eudev

Older Gentoo installs were using udev as the main virtual/udev provider. Based on bug #575718 it was changed to eudev. However, the rc service is still /etc/init.d/udev.

Configuration

Files

/etc/rc.conf

The global OpenRC configuration file.

Logging

OpenRC doesn't log anything by default. To log OpenRC's output during boot, uncomment and set the rc_logger option in /etc/rc.conf. The log will be saved at /var/log/rc.log by default.

Network management

OpenRC can be used with one of several network managers or even with none. By default in Gentoo's OpenRC profilesnetifrc scripts are utilized to manage network connections.

See the Network manager article for a list of options on network management.

Dependency behavior

Changing the default dependencies of init scripts, might be needed to fit more complex setups. See /etc/rc.conf for how to change the default behavior; notice the rc_depend_strict option. In addition, next networking examples show how flexible OpenRC can be.

Multiple network interfaces (example)

The SSH service must come up with the internal network, for instance eth0 and never wlan0.

Overrule the 'net' dependency from /etc/init.d/sshd, and refine it to depend on 'net.eth0':

Multiple network interfaces in multiple runlevels (example)

The SSH service must start with eth0 (not wlan0) in 'default' runlevel, but in 'office' runlevel it must start with wlan0 (not eth0).

Keep the default:

Make additional symlinks to sshd with the network interface names:

Settings are read from /etc/conf.d/sshd.eth0 and /etc/conf.d/sshd.wlan0 now:

Add the dependencies:

In this example net.eth0 and net.wlan0 read their settings from /etc/conf.d/net, or /etc/conf.d/net.office depending on the active runlevel. Add all runscripts to the different runlevels:

To switch between 'default' runlevel and 'office' runlevel without rebooting the computer, change to 'nonetwork' runlevel in between. The network interfaces will be stopped this way, and re-read their runlevel specific configuration. This works best when 'nonetwork' is a stacked runlevel in both the 'default' and 'office' runlevels, and the display manager and other non-network services are added to the 'nonetwork' runlevel only.

Selecting a specific runlevel at boot

OpenRC reads the kernel command-line used at boot time, and will start the runlevel specified by the 'softlevel' parameter if provided, instead of 'default'.

For instance, you can choose whether to boot into the 'default' or 'nonetwork' runlevels with the following example grub.conf configuration:

Usage

Runlevels

OpenRC can be controlled and configured using openrc, rc-update and rc-status commands.

Delete a service from default runlevel, where <service> is the name of the service to be removed:

Listing

Listing commands do not need to be ran as root.

Use rc-update show -v to display all available init scripts and their current runlevel (if they have been added to one):

Running rc-update or rc-update show will display only the init scripts that have been added to a runlevel.

Alternatively, the rc-status command can be used with the --servicelist (-s) option to view the state of all services:

Named runlevels

OpenRC runlevels are directories living in /etc/runlevels to create additional runlevels is enough to issue:

Stacked runlevels

Is possible manage variants using rc-update -s.

An usage example for using stacked runlevel on laptop to group networking services based on location is at OpenRC/StackedRunlevel.

Prefix

Gentoo Prefix installs Gentoo within an offset, known as a prefix, allowing users to install Gentoo in another location in the filesystem hierarchy, hence avoiding conflicts. Next to this offset, Gentoo Prefix runs unprivileged, meaning no root user or rights are required to use it.

By using an offset (the 'prefix' location), it is possible for many 'alternative' user groups to benefit from a large part of the packages in the Gentoo Linux Portage tree. Currently users of the following systems successfully run Gentoo Prefix: Mac OS X on PPC and x86, Linux on x86, x86_64 and ia64, Solaris 10 on Sparc, Sparc/64, x86 and x86_64, FreeBSD on x86, AIX on PPC, Interix on x86, Windows on x86 (with the help of Interix), HP-UX on PARISC and ia64.

OpenRC runscript already support prefix-installed daemons, during the Summer of Code 2012 work will be done to implement full secondary/session daemon behavior to complete the overall feature set provided by Prefix.

OpenRC/Prefix, a tutorial for trying it out.

Hotplug

OpenRC can be triggered by external events, such as new hardware from udev. See OpenRC/Event driven subarticle for details.

Manually recovering crashed services

If you have a process that crashes upon start you will see the following when you go to check it's status.

To remedy this situation you will need to zap the process which in the following example is the docker service.

Automatic respawning crashed services

Gentoo Docker Systemd

OpenRC can return state of services to runlevel setting state, to provide stateful init scripts and automatic respawning. What you need is to run openrc (for default runlevel). Crashed services start and manual run services will stop. To prevent this you can run openrc -n (--not-stop)

By default openrc will attempt just to start crashed services, not restart. This сontrolled by rc_crashed_stop (default NO) and rc_crashed_start (default YES) options in /etc/rc.conf.

CGroups support

OpenRC starting with version 0.12 has extended cgroups support. See OpenRC/CGroups for details.

Chroot support

Docker Gentoo Portage