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- .TH DINIT "1" "June 2017" "Dinit 0.06" "Dinit \- service management system"
- .SH NAME
- dinit \- supervise processes and manage services
- .\"
- .SH SYNOPSIS
- .\"
- .B dinit
- [\-s] [\-d \fIdir\fR] [\-p \fIpath\fR] [\fIservice-name\fR]
- .\"
- .SH DESCRIPTION
- .\"
- \fBDinit\fR is a process supervisor and service manager which can also
- function as a system \fBinit\fR 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.
- .LP
- Dinit reads service descriptions from files located in the service
- description directory, normally \fI/etc/dinit.d\fR for the system instance
- or \fI$HOME/dinit.d\fR when run as a user process. See \fBSERVICE
- DESCRIPTION FILES\fR for details.
- .\"
- .SH OPTIONS
- .TP
- \fB\-d\fR \fIdir\fP, \fB\-\-services\-dir\fR \fIdir\fP
- Specifies \fIdir\fP as the directory containing service definition files.
- .TP
- \fB\-p\fR \fIpath\fP, \fB\-\-socket-path\fR \fIpath\fP
- Species \fIpath\fP as the path to the control socket used to listen for
- commands from the \fBdinitctl\fR program.
- .TP
- \fB\-s\fR, \fB\-\-system\fR
- Run as the system init process. This is the default if invoked as PID 1.
- This option affects the default service definition directory and
- control socket path.
- .TP
- \fB\-\-help\fR
- display this help and exit
- .TP
- \fIservice-name\fR
- Specifies the name of the service that should be started (along with its
- dependencies). If not specified, defaults to \fIboot\fR (which requires
- that a suitable service description for the \fIboot\fR service exists).
- .\"
- .SH SERVICE DESCRIPTION FILES
- .\"
- Service description files specify the various attributes of a service. A
- service description file is named after the service it represents, and is
- a plain-text file with simple key-value format. The description files are
- located in the service description directory (which defaults to
- \fI/etc/dinit.d\fR for the system process).
- .LP
- All services have a \fItype\fR and a set of \fIdependencies\fR. Service
- types are discussed in the following subsection. If a service depends on
- another service, then starting the first service causes the second to start
- also (and the second service must complete its startup before the first
- is considered started). Similarly, if one service depends on another which
- becomes stopped, the first service must also stop.
- .LP
- Service description files are read by Dinit on an "as needed" basis. Once a
- service description has been read there is no way (yet) to alter it.
- .\"
- .SS SERVICE TYPES
- .\"
- There are four basic types of service:
- .IP \(bu
- \fBProcess\fR services. This kind of service runs as a single process; starting
- the service simply requires starting the process; stopping the service is
- accomplished by stopping the process (via sending it a signal).
- .IP \(bu
- \fBBgprocess\fR services ("background process" services). This kind of
- service is similar to a regular process service, but the process daemonizes
- or otherwise forks from the original process which starts it, and the
- process ID is written to a file. Dinit can read the process ID from the
- file and, if it is running as the system init process, can supervise it.
- .IP \(bu
- \fBScripted\fR services are services which are started and stopped by a
- command (which need not actually be a script, despite the name). They can
- not be supervised.
- .IP \(bu
- \fBInternal\fR services do not run as an external process at all. They can
- be started and stopped without any external action. They are useful for
- grouping other services (via service dependencies).
- .\"
- .SS SERVICE PROPERTIES
- .\"
- This section described the various service properties that can be specified
- in a service description file. Each line of the file can specify a single
- property value, expressed as "\fIproperty-name\fR = \fIvalue\fR". Comments
- begin with a hash mark (#) and extend to the end of the line (they must be
- separated from setting values by at least one whitespace character). Values
- are interpreted literally, except that:
- .\"
- .IP \(bu
- White space (comprised of spaces, tabs, etc) is collapsed to a single space.
- .IP \(bu
- Double quotes (") can be used around all or part of a property value, to
- prevent whitespace collapse and prevent interpretation of other special
- characters (such as "#") inside the quotes. The quote characters are not
- considered part of the parameter value.
- .IP \(bu
- A backslash (\\) can be used to escape the next character, causing it to
- lose any special meaning and become part of the property value. A double
- backslash (\\\\) is collapsed to a single backslash within the parameter
- value.
- .LP
- The following properties can be specified:
- .TP
- \fBtype\fR = {process | bgprocess | scripted | internal}
- Specifies the service type.
- .TP
- \fBcommand\fR = \fIcommand-string\fR
- Specifies the command, including command-line arguments, for starting the
- process. Applies only to \fBprocess\fR, \fBbgprocess\fR and \fBscripted\fR
- services.
- .TP
- \fBstop\-command\fR = \fIcommand-string\fR
- Specifies the command to stop the service. Applicable only to \fBscripted\fR
- services.
- .TP
- \fBrestart\fR = {yes | true | no | false}
- Indicates whether the service should automatically restart if it stops for
- any reason (including unexpected process termination, service dependency
- stopping, or user-initiated service stop).
- .TP
- \fBsmooth-recovery\fR = {yes | true | no | false}
- Applies only to \fBprocess\fR and \fBbgprocess\fR services. When set true/yes,
- an automatic process restart can be performed without first stopping any
- dependent services. This setting is meaningless if the \fBrestart\fR setting
- is set to false.
- .TP
- \fBrestart-delay\fR = \fIXXX.YYYY\fR
- Specifies the minimum time between automatic restarts. Enforcing a sensible
- minimum prevents Dinit from consuming a large number of process cycles in
- case a process continuously fails immediately after it is started. The
- default is 0.2 (200 milliseconds).
- .TP
- \fBrestart-limit-interval\fR = \fIXXX.YYYY\fR
- Sets the interval, in seconds, over which restarts are limited. If a process
- automatically restarts more than a certain number of times (specified by the
- \fBrestart-limit-count\fR setting) in this time interval, it will not restart
- again. The default value is 10 seconds.
- .TP
- \fBrestart-limit-count\fR = \fINNN\fR
- Specifies the maximum number of times that a service can automatically restart
- over the interval specified by \fBrestart-limit-interval\fR. Specify a value
- of 0 to disable the restart limit.
- .TP
- \fBpid-file\fR = \fIpath-to-file\fR
- For \fBbgprocess\fR type services only; specifies the path of the file where
- daemon will write its process ID before detaching. Dinit will read the
- contents of this file when starting the service, once the initial process
- exits, will supervise the process with the discovered process ID, and may
- send signals to the process ID to stop the service; if Dinit runs as a
- privileged user the path should therefore not be writable by unprivileged
- users.
- .TP
- \fBdepends-on\fR = \fIservice-name\fR
- This service depends on the named service. Starting this service will start
- the named service; the command to start this service will not be executed
- until the named service has started. If the named service is stopped then
- this service will also be stopped.
- .TP
- \fBwaits-for\fR = \fIservice-name\fR
- When this service is started, wait for the named service to finish starting
- (or to fail starting) before commencing the start procedure for this service.
- Starting this service will automatically start the named service. If the
- named service fails to start, this service will start as usual (subject to
- other dependencies being met).
- .TP
- \fBsocket-listen\fR = \fIsocket-path\fR
- Pre-open a socket for the service and pass it to the service using the
- \fBsystemd\fR activation protocol. This by itself does not give so called
- "socket activation", but does allow that any process trying to connect to the
- specified socket will be able to do so, even before the service is properly
- prepared to accept connections.
- .TP
- \fBsocket-permissions\fR = \fIoctal-permissions-mask\fR
- Gives the permissions for the socket specified using \fBsocket-listen\fR.
- Normally this will be 600 (user access only), 660 (user and group
- access), or 666 (all users). The default is 666.
- .TP
- \fBsocket-uid\fR = {\fInumeric-user-id\fR | \fIusername\fR}
- Specifies the user that should own the activation socket. If
- \fBsocket-uid\fR is specified without also specifying \fBsocket-gid\fR, then
- the socket group is the primary group of the specified user (as found in the
- system user database, normally \fI/etc/passwd\fR). If the socket owner is not
- specified, the socket will be owned by the user id of the Dinit process.
- .TP
- \fBsocket-gid\fR = {\fInumeric-group-id\fR | \fIgroup-name\fR}
- Specifies the group of the activation socket. See discussion of
- \fBsocket-uid\fR.
- .TP
- \fBtermsignal\fR = {HUP | INT | QUIT | USR1 | USR2}
- Specifies an additional signal to send to the process when requesting it
- to terminate (applies to 'process' services only). SIGTERM is always
- sent along with the specified signal, unless the \fBnosigterm\fR option is
- specified via the \fBoptions\fR parameter.
- .TP
- \fBoptions\fR = {runs\-on\-console | nosigterm | starts\-rwfs | starts\-log}...
- Specifies various options for this service:
- .RS
- .TP
- \fBno-sigterm\fR
- specifies that the TERM signal should not be send to the process to terminate
- it. (Another signal can be specified using the \fBtermsignal\fR setting; if no
- other signal is specified, no signal will be sent, which usually means that
- the service will not terminate).
- .TP
- \fBruns-on-console\fR
- specifies that this service uses the console; its input and output should be
- directed to the console (or precisely, to the device to which Dinit's standard
- output stream is connected). A service running on the console prevents other
- services from running on the console (they will queue for the console).
- The \fIinterrupt\fR key (normally control-C) will be active for process / scripted
- services that run on the console. Handling of an interrupt is determined by
- the service process, but typically will cause it to terminate.
- .TP
- \fBstarts-on-console\fR
- specifies that this service uses the console during service startup. This is
- implied by \fBruns-on-console\fR, but can be specified separately for services
- that need the console while they start but not afterwards.
- This setting is not applicable to regular \fBprocess\fR services, but can be
- used for \fBscripted\fR and \fBbgprocess\fR services. It allows for
- interrupting startup via the \fIinterrupt\fR key (normally control-C). This is
- useful to allow filesystem checks to be interrupted/skipped.
- .TP
- \fBstarts-rwfs\fR
- this service mounts the root filesystem read/write (or at least mounts the
- normal writable filesystems for the system). This prompts Dinit to create its
- control socket, if it has not already managed to do so.
- .TP
- \fBstarts-log\fR
- this service starts the system log daemon. Dinit will begin logging via the
- \fI/dev/log\fR socket.
- .TP
- \fBpass-cs-fd\fR
- pass an open Dinit control socket to the process when launching it (the
- \fIDINIT_CS_FD\fR environment variable will be set to the file descriptor of
- the socket). This allows the service to issue commands to Dinit even if the
- regular control socket is not available yet.
- Using this option has security implications! The service which receives the
- control socket must close it before launching any untrusted processes. You
- should not use this option unless the service is designed to receive a Dinit
- control socket.
- .RE
- .TP
- \fBlogfile\fR = \fIlog-file-path\fR
- Specifies the log file for the service. Output from the service process
- will go this file.
- .LP
- The next section contains example service descriptions including some of the
- parameters and options described above.
- .\"
- .SS EXAMPLES
- .LP
- Here is an example service description for the \fBmysql\fR database server.
- It has a dependency on the \fBrcboot\fR service (not shown) which is
- expected to have set up the system to a level suitable for basic operation.
- .RS
- .nf
- .gcolor yellow
- # mysqld service
- type = process
- command = /usr/bin/mysqld --user=mysql
- logfile = /var/log/mysqld.log
- smooth-recovery = true
- restart = false
- depends-on = rcboot # Basic system services must be ready
- .gcolor
- .RE
- .fi
- .LP
- Here is an examples for a filesystem check "service", run by a script
- (\fI/etc/dinit.d/rootfscheck.sh\fR). The script may need to reboot the
- system, but the control socket may not have been created, so it uses the
- \fBpass-cs-fd\fR option to allow the \fBreboot\fR command to issue control
- commands to Dinit. It runs on the console, so that output is visible and
- the process can be interrupted using control-C.
- .RS
- .nf
- .gcolor yellow
- # rootfscheck service
- type = scripted
- command = /etc/dinit.d/rootfscheck.sh
- restart = false
- options = starts-on-console pass-cs-fd
- depends-on = early-filesystems # /proc and /dev
- depends-on = device-node-daemon
- .gcolor
- .fi
- .RE
- More examples are provided with the Dinit distribution.
- .\"
- .SH SIGNALS
- .LP
- When run as a system process, 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.
- LP
- When run as a user process, SIGINT and SIGTERM both stop services and exit Dinit; SIGQUIT exits Dinit
- immediately.
- .\"
- .SH SEE ALSO
- .\"
- \fBdinitctl\fR(1).
- .\"
- .SH AUTHOR
- Dinit, and this manual, were written by Davin McCall.
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