DINIT(8) Dinit - service management system DINIT(8)

dinit - supervise processes and manage services

dinit [OPTION]... [service-name]...

Dinit is a process supervisor and service manager which can also function as a system init process. It has a small but functional feature set, offering service dependency handling, parallel startup, automatic rate-limited restart of failing processes, and service control functions.

Dinit can be run as a system instance (when run as the root user or when specified via command line parameter) or as a user instance. This affects the default paths used to locate certain files.

When run as PID 1, the first process, Dinit by default acts as a system manager and shuts down or reboots the system on request (including on receipt of certain signals). This is currently fully supported only on Linux. See RUNNING AS SYSTEM MANAGER / PRIMARY INIT.

Dinit reads service descriptions from files located in a service description directory, normally one of /etc/dinit.d, /run/dinit.d, /usr/local/lib/dinit.d and /lib/dinit.d for the system instance or $XDG_CONFIG_HOME/dinit.d and $HOME/.config/dinit.d when run as a user process. See SERVICE DESCRIPTION FILES for details of the service description format.

Specifies dir as the directory containing service definition files. This can be specified multiple times for multiple service directories. The default directories are not searched for services when this option is provided.

If not specified, the default for the user instance is $XDG_CONFIG_HOME/dinit.d and $HOME/.config/dinit.d or, for the system instance, each of /etc/dinit.d, /run/dinit.d/, /usr/local/lib/dinit.d, and /lib/dinit.d (searched in that order).

Read initial environment from file. For the system init process, the default is /etc/dinit/environment; see FILES.
Specifies path as the path to the control socket used to listen for commands from the dinitctl program. The default for the system service manager is usually /dev/dinitctl (but can be configured at build time). For a user service manager the default is either $XDG_RUNTIME_DIR/dinitctl or $HOME/.dinitctl, depending on whether $XDG_RUNTIME_DIR is set.
Specifies fd as the file descriptor number to report readiness to. Readiness means that the control socket is open and the service manager is ready to accept commands (e.g. via dinitctl). It does not mean that services are finished starting yet. The path to the currently open control socket is written on the file descriptor.
Species path as the path to the log file, to which Dinit will log status and error messages. Using this option inhibits logging via the syslog facility, however, all logging messages are duplicated as usual to the console (as long as --quiet has not also been specified). Note that when running as the system init, Dinit will continue if it cannot open the specified file, and will attempt to open it again once the root file system is writable. If not running as the system init and the file cannot be opened, Dinit will immediately exit with an error.
Run as the system service manager. This is the default if invoked as the root user. This option affects the default service definition directory and control socket path.
Run as the system manager (perform operations directly related to machine startup and shutdown). This is the default when running as process ID 1. The main user-visible effect of this option is to invoke the shutdown program when a shutdown is requested (and after all services have stopped), and to provide some basic support for system recovery in case the boot service (or other specified service) cannot be started.
Run as a user service manager. This is the opposite of --system, and is the default if not invoked as the root user.
Run in "container mode", i.e. do not perform system management functions (such as shutdown/reboot). The dinit daemon will simply exit rather than executing the shutdown program.
Run with no output to the terminal/console. This disables service status messages and sets the log level for the console log to none. To re-enable (some) output, use the --console-level option after this option.
Specify the path to resolve relative cgroup paths against. If service description settings contain relative cgroup paths, they will be resolved relative to this path. This option is only available if dinit is built with cgroups support.
Display brief help text and then exit.
Display version number and then exit.
[-t] service-name, [--service] service-name
Specifies the name of a service that should be started (along with its dependencies). If none are specified, defaults to boot (which requires that a suitable service description for the boot service exists). Multiple services can be specified in which case they will each be started.

Note: on Linux, if dinit is running as PID 1 and with UID 0, it may ignore "naked" service names (without preceding --service/-t) provided on the command line. See the COMMAND LINE FROM KERNEL section.

Specify the minimum log level of messages that should be logged to the console. From highest to lowest, the levels are error, warn, info and debug. Use a level of none to suppress all messages. Note that unless --quiet (-q) is also specified, service state change messages (service started, stopped etc) are always output.
Specify the minimum log level of messages that should be sent to the primary log (syslog facility or file). From highest to lowest, the levels are error, warn, info and debug. Use a level of none to suppress all messages.

Service description files specify the parameters of each service. They are named for the service they describe, and are found in one of several directories (including /etc/dinit.d) for a system instance or $XDG_CONFIG_HOME/dinit.d and $HOME/.config/dinit.d for a user instance (see also --services-dir option).

Service description files are read by Dinit on an "as needed" basis. Once loaded, a service description is never automatically unloaded (even if the service stops or fails). A service description can however be unloaded (if the service is stopped) or reloaded (with some limitations) via dinitctl(8) using the unload and reload subcommands respectively.

See dinit-service(5) for details of the format and available parameters.

There are two service names that are "special" to Dinit.

The boot service is the service that Dinit starts by default, if no other service names are provided when it is started.

The recovery service is a service that Dinit will offer to start if boot appears to fail (that is, if all services stop without a shutdown command having been issued), when Dinit is running as system manager.

On starting, Dinit starts the initial service(s) as specified on the command line. Starting a service also causes the dependencies of that service to start, and any service processes will not be launched until the dependencies are satisfied. Similarly, stopping a service first stops any dependent services.

During execution, Dinit accepts commands via a control socket which is created by Dinit when it starts. This can be used to order that a service be started or stopped, to determine service status, or to make certain configuration changes. See dinitctl(8) for details. Dinit attempts to check for the existence of an already-active socket first, and will refuse to start if one exists. Unfortunately, this check cannot be done atomically, and should not be relied upon generally as a means to avoid starting two instances of dinit.

Process-based services are monitored and, if the process terminates, the service may be stopped or the process may be re-started, according to the configuration in the service description.

Once all services stop, the dinit daemon will itself terminate (or, if running as system manager, will perform the appropriate type of system shutdown).

Dinit does no character set translation. Dinit's own output is in the execution character set as determined at compilation, as is the interpretation of input. Service names (and other user-defined inputs) are interpreted as byte sequences and are output as they were read. In general, modern systems use the UTF-8 character set universally and no problems will arise; however, systems configured to use other character sets may see odd behaviour if the input character set does not match the output character set, or if either input or output character sets are not a superset of the execution character set.

Running as the system manager (primary init) is currently supported only on Linux. When run as process ID 1, the dinit daemon by default assumes responsibility for system shutdown and restart (partially relying on external utilities which are part of the Dinit distribution).

When not running as a system manager, dinit assumes responsibility only for service management. System shutdown or restart need to be handled by the primary init, which should start dinit on normal startup, and terminate dinit before shutdown, by signalling it and waiting for it to terminate after stopping services (possibly by invoking dinitctl shutdown).

Dinit "logs" via two mechanisms simultaneously: the "console" (standard output, not necessarily associated with an actual console if dinit was started with output directed elsewhere) and the "main log facility" which is the syslog facility by default but which may be directed to a file.

Various options are available to control the types and "levels" of message that will be sent to each facility, and the destination of the main facility. The levels available (from low to high) are debug, notice, warn, and error. Selecting a particular log level for facility will cause the facility to receive messages of that level and higher. The special level none inhibits a facility from receiving any messages.

Service status messages (service started or stopped) have a nominal level of notice, except for failure which has a level of error or warn in case of transitive failure (due to a dependency). These messages are, by default, always issued to the console regardless of level, unless the --quiet (-q) option has been used.

To debug boot issues it may be useful to use -q (which also sets the level to none) and then also reset the level via the --console-level option to either warn or error. This will reduce noise in the output from successful service startup.

When running as PID 1, dinit may process the command line differently, to compensate for kernel behaviour.

On Linux, kernel command line options that are not recognised by the kernel will be passed on to dinit. However, bugs in some kernel versions may cause some options that are recognised to also be passed to dinit. Also, boot managers may insert command-line options such as "auto" (which indicates an "unattended" boot). Therefore, dinit ignores all "word like" options other than "single", which it treats as the name of the service to start (thus allowing "single user mode", assuming that a suitable service description exists). Options beginning with "--" will not be recognised by the kernel and will be passed to (and processed by) dinit; for example --quiet can be used to suppress console output. Options containing "=" that are unrecognised by the kernel (or some that are, due to bugs) are passed to init via the environment rather than via the command line.

There are several ways to work around this. Service names following the --container (-o) or --system-mgr (-m) options are not ignored. Also, the --service (-t) option can be used to force a service name to be recognised regardless of operating mode.

Default location of the environment file for Dinit when run as a system instance (for user instances there is no default). Values are specified as NAME=VALUE, one per line, and add to and replace variables present in the environment when Dinit started (the "original environment"). Lines beginning with a hash character (#) are ignored.
The following special commands can be used (each on a single line):
Clears the environment completely (prevents inheritance of any variables from the original environment).
!unset var-name...
Unsets the specified variables. Any previously specified value for these variables is forgotten, and they will not inherit any value from the original environment.
!import var-name...
Imports the value of the named variables from the original environment, overriding the effect of any value set previously as well as the effect of previous !unset and !clear commands.
/etc/dinit.d, /run/dinit.d, /usr/local/lib/dinit.d, /lib/dinit.d
Default locations for service description files. The directories are searched in the order listed.
$XDG_CONFIG_HOME/dinit.d, $HOME/.config/dinit.d
Default location for service description files for user instances. The directories are searched in the order listed.

When run as a system manager, SIGINT stops all services and performs a reboot (on Linux, this signal can be generated using the control-alt-delete key combination); SIGTERM stops services and halts the system; and SIGQUIT performs an immediate shutdown with no service rollback.

When run as a user process or system service manager only, SIGINT and SIGTERM both stop services and exit Dinit; SIGQUIT exits Dinit immediately.

dinitctl(8), dinit-service(5), dinitcheck(8), shutdown(8).

Dinit, and this manual, were written by Davin McCall.

November 2023 Dinit 0.17.2pre