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3 3
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7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-rcscripts.xml,v 1.30 2007/07/08 01:40:55 nightmorph Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-rcscripts.xml,v 1.35 2011/08/17 07:57:23 swift Exp $ -->
8 8
9<sections> 9<sections>
10 10
11<abstract> 11<abstract>
12Gentoo uses a special initscript format which, amongst other features, allows 12Gentoo uses a special initscript format which, amongst other features, allows
13dependency-driven decisions and virtual initscripts. This chapter explains all 13dependency-driven decisions and virtual initscripts. This chapter explains all
14these aspects and explains how to deal with these scripts. 14these aspects and explains how to deal with these scripts.
15</abstract> 15</abstract>
16 16
17<version>1.24</version> 17<version>4</version>
18<date>2007-07-07</date> 18<date>2011-08-17</date>
19 19
20<section> 20<section>
21<title>Runlevels</title> 21<title>Runlevels</title>
22<subsection> 22<subsection>
23<title>Booting your System</title> 23<title>Booting your System</title>
383configuration file called <path>/etc/conf.d/apache2</path>, which can contain 383configuration file called <path>/etc/conf.d/apache2</path>, which can contain
384the options you want to give to the Apache 2 server when it is started: 384the options you want to give to the Apache 2 server when it is started:
385</p> 385</p>
386 386
387<pre caption="Variable defined in /etc/conf.d/apache2"> 387<pre caption="Variable defined in /etc/conf.d/apache2">
388APACHE2_OPTS="-D PHP4" 388APACHE2_OPTS="-D PHP5"
389</pre> 389</pre>
390 390
391<p> 391<p>
392Such a configuration file contains variables and variables alone (just like 392Such a configuration file contains variables and variables alone (just like
393<path>/etc/make.conf</path>), making it very easy to configure services. It also 393<path>/etc/make.conf</path>), making it very easy to configure services. It also
438} 438}
439 439
440stop() { 440stop() {
441 <comment>(Commands necessary to stop the service)</comment> 441 <comment>(Commands necessary to stop the service)</comment>
442} 442}
443
444restart() {
445 <comment>(Commands necessary to restart the service)</comment>
446}
447</pre> 443</pre>
448 444
449<p> 445<p>
450Any init script <e>requires</e> the <c>start()</c> function to be defined. All 446Any init script <e>requires</e> the <c>start()</c> function to be defined. All
451other sections are optional. 447other sections are optional.
456<subsection> 452<subsection>
457<title>Dependencies</title> 453<title>Dependencies</title>
458<body> 454<body>
459 455
460<p> 456<p>
461There are two dependencies you can define: <c>use</c> and <c>need</c>. As we 457There are two dependency-alike settings you can define that influence the
462have mentioned before, the <c>need</c> dependency is more strict than the 458start-up or sequencing of init scripts: <c>use</c> and <c>need</c>. Next to
463<c>use</c> dependency. Following this dependency type you enter the service 459these two, there are also two order-influencing methods called <c>before</c> and
464you depend on, or the <e>virtual</e> dependency. 460<c>after</c>. These last two are no dependencies per se - they do not make the
461original init script fail if the selected one isn't scheduled to start (or fails
462to start).
463</p>
464
465<ul>
466 <li>
467 The <c>use</c> settings informs the init system that this script <e>uses</e>
468 functionality offered by the selected script, but does not directly depend
469 on it. A good example would be <c>use logger</c> or <c>use dns</c>. If those
470 services are available, they will be put in good use, but if you do not have
471 a logger or DNS server the services will still work. If the services exist,
472 then they are started before the script that <c>use</c>'s them.
473 </li>
474 <li>
475 The <c>need</c> setting is a hard dependency. It means that the script that
476 is <c>need</c>'ing another script will not start before the other script is
477 launched successfully. Also, if that other script is restarted, then this
478 one will be restarted as well.
479 </li>
480 <li>
481 When using <c>before</c>, then the given script is launched before the
482 selected one <e>if</e> the selected one is part of the init level. So an
483 init script <path>xdm</path> that defines <c>before alsasound</c> will start
484 before the <path>alsasound</path> script, but only if <path>alsasound</path>
485 is scheduled to start as well in the same init level. If
486 <path>alsasound</path> is not scheduled to start too, then this particular
487 setting has no effect and <path>xdm</path> will be started when the init
488 system deems it most appropriate.
489 </li>
490 <li>
491 Similarly, <c>after</c> informs the init system that the given script should
492 be launched after the selected one <e>if</e> the selected one is part of the
493 init level. If not, then the setting has no effect and the script will be
494 launched by the init system when it deems it most appropriate.
495 </li>
496</ul>
497
498<p>
499It should be clear from the above that <c>need</c> is the only "true" dependency
500setting as it affects if the script will be started or not. All the others are
501merely pointers towards the init system to clarify in which order scripts can be
502(or should be) launched.
503</p>
504
505<p>
506Now, if you look at many of Gentoo's available init scripts, you will notice
507that some have dependencies on things that are no init scripts. These "things"
508we call <e>virtuals</e>.
465</p> 509</p>
466 510
467<p> 511<p>
468A <e>virtual</e> dependency is a dependency that a service provides, but that is 512A <e>virtual</e> dependency is a dependency that a service provides, but that is
469not provided solely by that service. Your init script can depend on a system 513not provided solely by that service. Your init script can depend on a system
513<subsection> 557<subsection>
514<title>Controlling the Order</title> 558<title>Controlling the Order</title>
515<body> 559<body>
516 560
517<p> 561<p>
518In some cases you might not require a service, but want your service to be 562As we described in the previous section, you can tell the init system what order
519started <c>before</c> (or <c>after</c>) another service <e>if</e> it is 563it should use for starting (or stopping) scripts. This ordering is handled both
520available on the system (note the conditional - this is no dependency anymore) 564through the dependency settings <c>use</c> and <c>need</c>, but also through the
521<e>and</e> run in the same runlevel (note the conditional - only services in the 565order settings <c>before</c> and <c>after</c>. As we have described these
522same runlevel are involved). You can provide this information using the 566earlier already, let's take a look at the Portmap service as an example of such
523<c>before</c> or <c>after</c> settings. 567init script.
524</p>
525
526<p>
527As an example we view the settings of the Portmap service:
528</p> 568</p>
529 569
530<pre caption="The depend() function in the Portmap service"> 570<pre caption="The depend() function in the Portmap service">
531depend() { 571depend() {
532 need net 572 need net
572<c>eend</c> functions to inform the user about what is happening: 612<c>eend</c> functions to inform the user about what is happening:
573</p> 613</p>
574 614
575<pre caption="Example start() function"> 615<pre caption="Example start() function">
576start() { 616start() {
617 if [ "${RC_CMD}" = "restart" ];
618 then
619 <comment># Do something in case a restart requires more than stop, start</comment>
620 fi
621
577 ebegin "Starting my_service" 622 ebegin "Starting my_service"
578 start-stop-daemon --start --exec /path/to/my_service \ 623 start-stop-daemon --start --exec /path/to/my_service \
579 --pidfile /path/to/my_pidfile 624 --pidfile /path/to/my_pidfile
580 eend $? 625 eend $?
581} 626}
589<c>start-stop-daemon</c> options, but this is not recommended unless the 634<c>start-stop-daemon</c> options, but this is not recommended unless the
590service is extremely verbose. Using <c>--quiet</c> may hinder debugging if the 635service is extremely verbose. Using <c>--quiet</c> may hinder debugging if the
591service fails to start. 636service fails to start.
592</p> 637</p>
593 638
639<p>
640Another notable setting used in the above example is to check the contents of
641the <c>RC_CMD</c> variable. Unlike the previous init script system, the newer
642<c>openrc</c> system does not support script-specific restart functionality.
643Instead, the script needs to check the contents of the <c>RC_CMD</c> variable
644to see if a function (be it <c>start()</c> or <c>stop()</c>) is called as part
645of a restart or not.
646</p>
647
594<note> 648<note>
595Make sure that <c>--exec</c> actually calls a service and not just a shell 649Make sure that <c>--exec</c> actually calls a service and not just a shell
596script that launches services and exits -- that's what the init script is 650script that launches services and exits -- that's what the init script is
597supposed to do. 651supposed to do.
598</note> 652</note>
602source code of the available init scripts in your <path>/etc/init.d</path> 656source code of the available init scripts in your <path>/etc/init.d</path>
603directory. 657directory.
604</p> 658</p>
605 659
606<p> 660<p>
607Other functions you can define are: <c>stop()</c> and <c>restart()</c>. You are 661Another function you can define is <c>stop()</c>. You are not obliged to define
608not obliged to define these functions! Our init system is intelligent enough to 662this function though! Our init system is intelligent enough to fill in this
609fill these functions by itself if you use <c>start-stop-daemon</c>. 663function by itself if you use <c>start-stop-daemon</c>.
610</p>
611
612<p> 664</p>
613Although you do not <e>have</e> to create a <c>stop()</c> function, here is an 665
614example: 666<p>
667Here is an example of a <c>stop()</c> function:
615</p> 668</p>
616 669
617<pre caption="Example stop() function"> 670<pre caption="Example stop() function">
618stop() { 671stop() {
619 ebegin "Stopping my_service" 672 ebegin "Stopping my_service"
649$ <i>man start-stop-daemon</i> 702$ <i>man start-stop-daemon</i>
650</pre> 703</pre>
651 704
652<p> 705<p>
653Gentoo's init script syntax is based on the Bourne Again Shell (bash) so you are 706Gentoo's init script syntax is based on the Bourne Again Shell (bash) so you are
654free to use bash-compatible constructs inside your init script. 707free to use bash-compatible constructs inside your init script. However, you may
708want to write your init scripts to be POSIX-compliant. Future init script
709systems may allow symlinking <path>/bin/sh</path> to other shells besides
710bash. Init scripts that rely on bash-only features will then break these
711configurations.
655</p> 712</p>
656 713
657</body> 714</body>
658</subsection> 715</subsection>
659<subsection> 716<subsection>
674 stop 731 stop
675 sleep 3 <comment># Wait 3 seconds before starting again</comment> 732 sleep 3 <comment># Wait 3 seconds before starting again</comment>
676 start 733 start
677} 734}
678</pre> 735</pre>
736
737<impo>
738The function <c>restart()</c> cannot be overridden in openrc!
739</impo>
679 740
680</body> 741</body>
681</subsection> 742</subsection>
682<subsection> 743<subsection>
683<title>Service Configuration Variables</title> 744<title>Service Configuration Variables</title>
759 net.eth0 | 820 net.eth0 |
760</pre> 821</pre>
761 822
762<p> 823<p>
763Even though <c>net.eth0</c> has been removed from the offline runlevel, 824Even though <c>net.eth0</c> has been removed from the offline runlevel,
764<c>udev</c> will still attempt to start any devices it detects and launch the 825<c>udev</c> might want to attempt to start any devices it detects and launch the
765appropriate services. Therefore, you will need to add each network service you 826appropriate services, a functionality that is called <e>hotplugging</e>. By
766do not want started (as well as services for any other devices that may be 827default, Gentoo does not enable hotplugging.
767started by udev) to <path>/etc/conf.d/rc</path> as shown. 828</p>
829
768</p> 830<p>
831If you do want to enable hotplugging, but only for a selected set of scripts,
832use the <c>rc_hotplug</c> variable in <path>/etc/rc.conf</path>:
833</p>
769 834
770<pre caption="Disabling device initiated services in /etc/conf.d/rc"> 835<pre caption="Disabling device initiated services in /etc/rc.conf">
771RC_COLDPLUG="yes" 836<comment># Allow net.wlan as well as any other service, except those matching net.*
772<comment>(Next, specify the services you do not want automatically started)</comment> 837# to be hotplugged</comment>
773RC_PLUG_SERVICES="!net.eth0" 838rc_hotplug="net.wlan !net.*"
774</pre> 839</pre>
775 840
776<note> 841<note>
777For more information on device initiated services, please see the comments 842For more information on device initiated services, please see the comments
778inside <path>/etc/conf.d/rc</path>. 843inside <path>/etc/rc.conf</path>.
779</note> 844</note>
780 845
781<p> 846<p>
782Now edit your bootloader configuration and add a new entry for the 847Now edit your bootloader configuration and add a new entry for the
783<c>offline</c> runlevel. For instance, in <path>/boot/grub/grub.conf</path>: 848<c>offline</c> runlevel. For instance, in <path>/boot/grub/grub.conf</path>:

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