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service-script-guide.md: formatting changes

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Add a title, adjust the headings and update the example that referred to
"net.lo" to refer to "loopback".
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William Hubbs 2018-01-08 15:33:03 -06:00
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service-script-guide.md
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@ -1,4 +1,6 @@
This document is aimed at upstream and distribution developers who # OpenRC Service Script Writing Guide
This document is aimed at developers or packagers who
write OpenRC service scripts, either for their own projects, or for write OpenRC service scripts, either for their own projects, or for
the packages they maintain. It contains advice, suggestions, tips, the packages they maintain. It contains advice, suggestions, tips,
tricks, hints, and counsel; cautions, warnings, heads-ups, tricks, hints, and counsel; cautions, warnings, heads-ups,
@ -11,7 +13,7 @@ don't consider anything exotic, and assume that you will use
start-stop-daemon to manage a fairly typical long-running UNIX start-stop-daemon to manage a fairly typical long-running UNIX
process. process.
# Don't write your own start/stop functions ## Don't write your own start/stop functions
OpenRC is capable of stopping and starting most daemons based on the OpenRC is capable of stopping and starting most daemons based on the
information that you give it. For a well-behaved daemon that information that you give it. For a well-behaved daemon that
@ -113,7 +115,7 @@ To recap, in order of preference:
to disable the daemon's PID file (or, to write it straight into the to disable the daemon's PID file (or, to write it straight into the
garbage), then do that, and use `command_background=true`. garbage), then do that, and use `command_background=true`.
# Reloading your daemon's configuration ## Reloading your daemon's configuration
Many daemons will reload their configuration files in response to a Many daemons will reload their configuration files in response to a
signal. Suppose your daemon will reload its configuration in response signal. Suppose your daemon will reload its configuration in response
@ -139,7 +141,7 @@ reload() {
} }
``` ```
# Don't restart/reload with a broken config ## Don't restart/reload with a broken config
Often, users will start a daemon, make some configuration change, and Often, users will start a daemon, make some configuration change, and
then attempt to restart the daemon. If the recent configuration change then attempt to restart the daemon. If the recent configuration change
@ -187,7 +189,7 @@ reload() {
} }
``` ```
# PID files should be writable only by root ## PID files should be writable only by root
PID files must be writable only by *root*, which means additionally PID files must be writable only by *root*, which means additionally
that they must live in a *root*-owned directory. that they must live in a *root*-owned directory.
@ -239,7 +241,7 @@ A decent example of this is the [Nagios core service
script](https://github.com/NagiosEnterprises/nagioscore/blob/master/openrc-init.in), script](https://github.com/NagiosEnterprises/nagioscore/blob/master/openrc-init.in),
where the full path to the PID file is specified at build-time. where the full path to the PID file is specified at build-time.
# Don't let the user control the PID file location ## Don't let the user control the PID file location
It's usually a mistake to let the end user control the PID file It's usually a mistake to let the end user control the PID file
location through a conf.d variable, for a few reasons: location through a conf.d variable, for a few reasons:
@ -267,7 +269,7 @@ pidfile="/run/${RC_SVCNAME}.pid"
guarantees that your PID file has a unique name. guarantees that your PID file has a unique name.
# Upstream your service scripts (for distribution developers) ## Upstream your service scripts (for packagers)
The ideal place for an OpenRC service script is **upstream**. Much like The ideal place for an OpenRC service script is **upstream**. Much like
systemd services, a well-crafted OpenRC service script should be systemd services, a well-crafted OpenRC service script should be
@ -292,7 +294,7 @@ service script in your own distribution's repository, then you have to
keep the command path and package synchronized yourself, and that's no keep the command path and package synchronized yourself, and that's no
fun. fun.
# Be wary of "need net" dependencies ## Be wary of "need net" dependencies
There are two things you need to know about "need net" dependencies: There are two things you need to know about "need net" dependencies:
@ -310,7 +312,7 @@ interface. We'll consider the two most common users of "need net";
network clients who access some network resource, and network servers network clients who access some network resource, and network servers
who provide them. who provide them.
## Network clients ### Network clients
Network clients typically want the WAN interface to be up. That may Network clients typically want the WAN interface to be up. That may
tempt you to depend on the WAN interface; but first, you should ask tempt you to depend on the WAN interface; but first, you should ask
@ -329,7 +331,7 @@ logged. The signature update service will not crash, and—perhaps more
importantly—you don't want it to terminate if the administrator turns importantly—you don't want it to terminate if the administrator turns
off the WAN interface for a second. off the WAN interface for a second.
## Network servers ### Network servers
Network servers are generally easier to handle than their client Network servers are generally easier to handle than their client
counterparts. Most server daemons listen on `0.0.0.0` (all addresses) counterparts. Most server daemons listen on `0.0.0.0` (all addresses)
@ -350,7 +352,7 @@ If your daemon can optionally be configured to listen on a particular
interface, then please see the "Depending on a particular interface" interface, then please see the "Depending on a particular interface"
section. section.
## Depending on a particular interface ### Depending on a particular interface
If you need to depend on one particular interface, usually it's not If you need to depend on one particular interface, usually it's not
easy to determine programmatically what that interface is. For easy to determine programmatically what that interface is. For
@ -371,8 +373,8 @@ like the following in the service configuration file,
```sh ```sh
# Specify the network service that corresponds to the "bind" setting # Specify the network service that corresponds to the "bind" setting
# in your configuration file. For example, if you bind to 127.0.0.1, # in your configuration file. For example, if you bind to 127.0.0.1,
# this should be set to "net.lo" which provides the loopback interface. # this should be set to "loopback" which provides the loopback interface.
rc_need="net.lo" rc_need="loopback"
``` ```
This is a sensible default for daemons that are happy with `0.0.0.0`, This is a sensible default for daemons that are happy with `0.0.0.0`,