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1<?xml version='1.0' encoding='UTF-8'?>
2<!DOCTYPE sections SYSTEM "/dtd/book.dtd">
3
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4<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-rcscripts.xml,v 1.8 2004/01/06 09:57:49 swift Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-rcscripts.xml,v 1.27 2006/10/28 09:17:55 neysx Exp $ -->
5 8
6<sections> 9<sections>
10
11<abstract>
12Gentoo uses a special initscript format which, amongst other features, allows
13dependency-driven decisions and virtual initscripts. This chapter explains all
14these aspects and explains how to deal with these scripts.
15</abstract>
16
17<version>1.22</version>
18<date>2006-09-07</date>
19
7<section> 20<section>
8<title>Runlevels</title> 21<title>Runlevels</title>
9<subsection> 22<subsection>
10<title>Booting your System</title> 23<title>Booting your System</title>
11<body> 24<body>
31services you need in order to have a successfully booted system. 44services you need in order to have a successfully booted system.
32</p> 45</p>
33 46
34<p> 47<p>
35Finally, when all scripts are executed, <c>init</c> activates the terminals 48Finally, when all scripts are executed, <c>init</c> activates the terminals
36(in most cases just the virtual consoles which are hidden beneith <c>Alt-F1</c>, 49(in most cases just the virtual consoles which are hidden beneath <c>Alt-F1</c>,
37<c>Alt-F2</c>, etc.) attaching a special process called <c>agetty</c> to it. 50<c>Alt-F2</c>, etc.) attaching a special process called <c>agetty</c> to it.
38This process will then make sure you are able to log on through these terminals 51This process will then make sure you are able to log on through these terminals
39by running <c>login</c>. 52by running <c>login</c>.
40</p> 53</p>
41 54
80configuration file that specifies what actions need to be taken. This 93configuration file that specifies what actions need to be taken. This
81configuration file is <path>/etc/inittab</path>. 94configuration file is <path>/etc/inittab</path>.
82</p> 95</p>
83 96
84<p> 97<p>
85If you remember the boot sequence we have just explained to you, you will 98If you remember the boot sequence we have just described, you will remember
86remember that <c>init</c>'s first action is to mount all filesystems. This is 99that <c>init</c>'s first action is to mount all filesystems. This is defined in
87defined in the following line from <path>/etc/inittab</path>: 100the following line from <path>/etc/inittab</path>:
88</p> 101</p>
89 102
90<pre caption="The system initialisation line in /etc/inittab"> 103<pre caption="The system initialisation line in /etc/inittab">
91si::sysinit:/sbin/rc sysinit 104si::sysinit:/sbin/rc sysinit
92</pre> 105</pre>
268<pre caption="Requesting a list of all services that require Postfix"> 281<pre caption="Requesting a list of all services that require Postfix">
269# <i>/etc/init.d/postfix needsme</i> 282# <i>/etc/init.d/postfix needsme</i>
270</pre> 283</pre>
271 284
272<p> 285<p>
273Finally, you can ask what dependencies the service requires but that are 286Finally, you can ask what dependencies the service requires that are missing:
274missing:
275</p> 287</p>
276 288
277<pre caption="Requesting a list of missing dependencies for Postfix"> 289<pre caption="Requesting a list of missing dependencies for Postfix">
278# <i>/etc/init.d/postfix broken</i> 290# <i>/etc/init.d/postfix broken</i>
279</pre> 291</pre>
287<title>What is rc-update?</title> 299<title>What is rc-update?</title>
288<body> 300<body>
289 301
290<p> 302<p>
291Gentoo's init system uses a dependency-tree to decide what service needs to be 303Gentoo's init system uses a dependency-tree to decide what service needs to be
292started first. As this is a tedious task that we wouldn't want our users to do 304started first. As this is a tedious task that we wouldn't want our users to
293manually, we have created tools that ease the administration of the runlevels 305have to do manually, we have created tools that ease the administration of the
294and init scripts. 306runlevels and init scripts.
295</p> 307</p>
296 308
297<p> 309<p>
298With <c>rc-update</c> you can add and remove init scripts to a runlevel. The 310With <c>rc-update</c> you can add and remove init scripts to a runlevel. The
299<c>rc-update</c> tool will then automatically ask the <c>depscan.sh</c> script 311<c>rc-update</c> tool will then automatically ask the <c>depscan.sh</c> script
339<subsection> 351<subsection>
340<title>Why the Need for Extra Configuration?</title> 352<title>Why the Need for Extra Configuration?</title>
341<body> 353<body>
342 354
343<p> 355<p>
344Init scripts can be quite complex. It is therefore not really interesting to 356Init scripts can be quite complex. It is therefore not really desirable to
345have the users directly edit the init script, as it would make it more 357have the users edit the init script directly, as it would make it more
346error-prone. It is however important to be able to configure such a service. For 358error-prone. It is however important to be able to configure such a service. For
347instance, you might want to give more options to the service itself. 359instance, you might want to give more options to the service itself.
348</p> 360</p>
349 361
350<p> 362<p>
351A second reason to have this configuration outside the init script is to be able 363A second reason to have this configuration outside the init script is to be
352to update the init scripts without being afraid that your configuration changes 364able to update the init scripts without the fear that your configuration
353are undone. 365changes will be undone.
354</p> 366</p>
355 367
356</body> 368</body>
357</subsection> 369</subsection>
358<subsection> 370<subsection>
385<subsection> 397<subsection>
386<title>Do I Have To?</title> 398<title>Do I Have To?</title>
387<body> 399<body>
388 400
389<p> 401<p>
390No. Writing an init script is usually not necessary as Gentoo provides 402No, writing an init script is usually not necessary as Gentoo provides
391ready-to-use init scripts for all provided services. However, you might have 403ready-to-use init scripts for all provided services. However, you might have
392installed a service without using Portage, in which case you will most likely 404installed a service without using Portage, in which case you will most likely
393have to create an init script. 405have to create an init script.
394</p> 406</p>
395 407
499 511
500<p> 512<p>
501In some cases you might not require a service, but want your service to be 513In some cases you might not require a service, but want your service to be
502started <c>before</c> (or <c>after</c>) another service <e>if</e> it is 514started <c>before</c> (or <c>after</c>) another service <e>if</e> it is
503available on the system (note the conditional - this is no dependency anymore) 515available on the system (note the conditional - this is no dependency anymore)
504<e>and</e> ran in the same runlevel (note the conditional - only services in the 516<e>and</e> run in the same runlevel (note the conditional - only services in the
505same runlevel are involved). You can provide this information using the 517same runlevel are involved). You can provide this information using the
506<c>before</c> or <c>after</c> settings. 518<c>before</c> or <c>after</c> settings.
507</p> 519</p>
508 520
509<p> 521<p>
518} 530}
519</pre> 531</pre>
520 532
521<p> 533<p>
522You can also use the "*" glob to catch all services in the same runlevel, 534You can also use the "*" glob to catch all services in the same runlevel,
523although this isn't adviseable. 535although this isn't advisable.
524</p> 536</p>
525 537
526<pre caption="Running an init script as first script in the runlevel"> 538<pre caption="Running an init script as first script in the runlevel">
527depend() { 539depend() {
528 before * 540 before *
529} 541}
530</pre> 542</pre>
531 543
544<p>
545If your service must write to local disks, it should need <c>localmount</c>. If
546it places anything in <path>/var/run</path> such as a pidfile, then should
547start after <c>bootmisc</c>:
548</p>
549
550<pre caption="Example depend() function">
551depend() {
552 need localmount
553 after bootmisc
554}
555</pre>
556
532</body> 557</body>
533</subsection> 558</subsection>
534<subsection> 559<subsection>
535<title>Standard Functions</title> 560<title>Standard Functions</title>
536<body> 561<body>
537 562
538<p> 563<p>
539Next to the <c>depend()</c> functionality, you also need to define the 564Next to the <c>depend()</c> functionality, you also need to define the
540<c>start()</c> function. This one contains all the commands necessary to 565<c>start()</c> function. This one contains all the commands necessary to
541initialize your service. It is adviseable to use the <c>ebegin</c> and 566initialize your service. It is advisable to use the <c>ebegin</c> and
542<c>eend</c> functions to inform the user about what is happening: 567<c>eend</c> functions to inform the user about what is happening:
543</p> 568</p>
544 569
545<pre caption="Example start() function"> 570<pre caption="Example start() function">
546start() { 571start() {
547 ebegin "Starting my_service" 572 ebegin "Starting my_service"
548 start-stop-daemon --start --quiet --exec /path/to/my_service 573 start-stop-daemon --start --exec /path/to/my_service \
574 --pidfile /path/to/my_pidfile
549 eend $? 575 eend $?
550} 576}
551</pre> 577</pre>
552 578
553<p> 579<p>
580Both <c>--exec</c> and <c>--pidfile</c> should be used in start and stop
581functions. If the service does not create a pidfile, then use
582<c>--make-pidfile</c> if possible, though you should test this to be sure.
583Otherwise, don't use pidfiles. You can also add <c>--quiet</c> to the
584<c>start-stop-daemon</c> options, but this is not recommended unless the
585service is extremely verbose. Using <c>--quiet</c> may hinder debugging if the
586service fails to start.
587</p>
588
589<note>
590Make sure that <c>--exec</c> actually calls a service and not just a shell
591script that launches services and exits -- that's what the init script is
592supposed to do.
593</note>
594
595<p>
554If you need more examples of the <c>start()</c> function, please read the source 596If you need more examples of the <c>start()</c> function, please read the
555code of the available init scripts in your <path>/etc/init.d</path> directory. 597source code of the available init scripts in your <path>/etc/init.d</path>
556As for <c>start-stop-daemon</c>, there is an excellent man page available if you 598directory.
557need more information:
558</p>
559
560<pre caption="Getting the man page for start-stop-daemon">
561# <i>man start-stop-daemon</i>
562</pre> 599</p>
563 600
564<p> 601<p>
565Other functions you can define are: <c>stop()</c> and <c>restart()</c>. You are 602Other functions you can define are: <c>stop()</c> and <c>restart()</c>. You are
566not obliged to define these functions! Our init system is intelligent enough to 603not obliged to define these functions! Our init system is intelligent enough to
567fill these functions in herself if you use <c>start-stop-daemon</c>. 604fill these functions by itself if you use <c>start-stop-daemon</c>.
605</p>
606
607<p>
608Although you do not <e>have</e> to create a <c>stop()</c> function, here is an
609example:
610</p>
611
612<pre caption="Example stop() function">
613stop() {
614 ebegin "Stopping my_service"
615 start-stop-daemon --stop --exec /path/to/my_service \
616 --pidfile /path/to/my_pidfile
617 eend $?
618}
619</pre>
620
621<p>
622If your service runs some other script (for example, bash, python, or perl),
623and this script later changes names (for example, <c>foo.py</c> to <c>foo</c>),
624then you will need to add <c>--name</c> to <c>start-stop-daemon</c>. You must
625specify the name that your script will be changed to. In this example, a
626service starts <c>foo.py</c>, which changes names to <c>foo</c>:
627</p>
628
629<pre caption="A service that starts the foo script">
630start() {
631 ebegin "Starting my_script"
632 start-stop-daemon --start --exec /path/to/my_script \
633 --pidfile /path/to/my_pidfile --name foo
634 eend $?
635}
636</pre>
637
638<p>
639<c>start-stop-daemon</c> has an excellent man page available if you need more
640information:
641</p>
642
643<pre caption="Getting the man page for start-stop-daemon">
644$ <i>man start-stop-daemon</i>
645</pre>
646
647<p>
648Gentoo's init script syntax is based on the Bourne Again Shell (bash) so you are
649free to use bash-compatible constructs inside your init script.
568</p> 650</p>
569 651
570</body> 652</body>
571</subsection> 653</subsection>
572<subsection> 654<subsection>
582 664
583<pre caption="Supporting the restartdelay option"> 665<pre caption="Supporting the restartdelay option">
584opts="${opts} restartdelay" 666opts="${opts} restartdelay"
585 667
586restartdelay() { 668restartdelay() {
587 stop() 669 stop
588 sleep 3 <comment># Wait 3 seconds before starting again</comment> 670 sleep 3 <comment># Wait 3 seconds before starting again</comment>
589 start() 671 start
590} 672}
591</pre> 673</pre>
592 674
593</body> 675</body>
594</subsection> 676</subsection>
615</p> 697</p>
616 698
617</body> 699</body>
618</subsection> 700</subsection>
619</section> 701</section>
702<section>
703<title>Changing the Runlevel Behaviour</title>
704<subsection>
705<title>Who might benefit from this?</title>
706<body>
707
708<p>
709Many laptop users know the situation: at home you need to start <c>net.eth0</c>
710while you don't want to start <c>net.eth0</c> while you're on the road (as
711there is no network available). With Gentoo you can alter the runlevel behaviour
712to your own will.
713</p>
714
715<p>
716For instance you can create a second "default" runlevel which you can boot that
717has other init scripts assigned to it. You can then select at boottime what
718default runlevel you want to use.
719</p>
720
721</body>
722</subsection>
723<subsection>
724<title>Using softlevel</title>
725<body>
726
727<p>
728First of all, create the runlevel directory for your second "default" runlevel.
729As an example we create the <path>offline</path> runlevel:
730</p>
731
732<pre caption="Creating a runlevel directory">
733# <i>mkdir /etc/runlevels/offline</i>
734</pre>
735
736<p>
737Add the necessary init scripts to the newly created runlevels. For instance, if
738you want to have an exact copy of your current <c>default</c> runlevel but
739without <c>net.eth0</c>:
740</p>
741
742<pre caption="Adding the necessary init scripts">
743<comment>(Copy all services from default runlevel to offline runlevel)</comment>
744# <i>cd /etc/runlevels/default</i>
745# <i>for service in *; do rc-update add $service offline; done</i>
746<comment>(Remove unwanted service from offline runlevel)</comment>
747# <i>rc-update del net.eth0 offline</i>
748<comment>(Display active services for offline runlevel)</comment>
749# <i>rc-update show offline</i>
750<comment>(Partial sample Output)</comment>
751 acpid | offline
752 domainname | offline
753 local | offline
754 net.eth0 |
755</pre>
756
757<p>
758Now edit your bootloader configuration and add a new entry for the
759<c>offline</c> runlevel. For instance, in <path>/boot/grub/grub.conf</path>:
760</p>
761
762<pre caption="Adding an entry for the offline runlevel">
763title Gentoo Linux Offline Usage
764 root (hd0,0)
765 kernel (hd0,0)/kernel-2.4.25 root=/dev/hda3 <i>softlevel=offline</i>
766</pre>
767
768<p>
769VoilĂ , you're all set now. If you boot your system and select the newly added
770entry at boot, the <c>offline</c> runlevel will be used instead of the
771<c>default</c> one.
772</p>
773
774</body>
775</subsection>
776<subsection>
777<title>Using bootlevel</title>
778<body>
779
780<p>
781Using <c>bootlevel</c> is completely analogous to <c>softlevel</c>. The only
782difference here is that you define a second "boot" runlevel instead of a second
783"default" runlevel.
784</p>
785
786</body>
787</subsection>
788</section>
620</sections> 789</sections>

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