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authorScott Rifenbark <srifenbark@gmail.com>2019-10-12 06:46:35 -0700
committerRichard Purdie <richard.purdie@linuxfoundation.org>2019-10-23 17:30:38 +0100
commit2c152f790abc91f661838df3b348f3374511d890 (patch)
treefe9ce9a505e3533536d35fbbe3a940163f7eedf8 /documentation/dev-manual
parenta6d1001b2a630b4e16713e59f468d7c52fc982e0 (diff)
downloadpoky-2c152f790abc91f661838df3b348f3374511d890.tar.gz
dev-manual: Added info to "Selecting an Initialization Manager"
(From yocto-docs rev: 4d5c70b394cfd7d7f189d719b4391f784bd57733) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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-rw-r--r--documentation/dev-manual/dev-manual-common-tasks.xml41
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diff --git a/documentation/dev-manual/dev-manual-common-tasks.xml b/documentation/dev-manual/dev-manual-common-tasks.xml
index 8bc7fd8b2b..a97c96619d 100644
--- a/documentation/dev-manual/dev-manual-common-tasks.xml
+++ b/documentation/dev-manual/dev-manual-common-tasks.xml
@@ -10810,6 +10810,47 @@
10810 </para> 10810 </para>
10811 10811
10812 <para> 10812 <para>
10813 By default, the Yocto Project uses SysVinit as the initialization
10814 manager.
10815 However, support also exists for systemd,
10816 which is a full replacement for init with
10817 parallel starting of services, reduced shell overhead and other
10818 features that are used by many distributions.
10819 </para>
10820
10821 <para>
10822 Within the system, SysVinit treats system components as services.
10823 These services are maintained as shell scripts stored in the
10824 <filename>/etc/init.d/</filename> directory.
10825 Services organize into different run levels.
10826 This organization is maintained by putting links to the services
10827 in the <filename>/etc/rcN.d/</filename> directories, where
10828 <replaceable>N/</replaceable> is one of the following options:
10829 "S", "0", "1", "2", "3", "4", "5", or "6".
10830 <note>
10831 Each runlevel has a dependency on the previous runlevel.
10832 This dependency allows the services to work properly.
10833 </note>
10834 </para>
10835
10836 <para>
10837 In comparison, systemd treats components as units.
10838 Using units is a broader concept as compared to using a service.
10839 A unit includes several different types of entities.
10840 Service is one of the types of entities.
10841 The runlevel concept in SysVinit corresponds to the concept of a
10842 target in systemd, where target is also a type of supported unit.
10843 </para>
10844
10845 <para>
10846 In a SysVinit-based system, services load sequentially (i.e. one
10847 by one) during and parallelization is not supported.
10848 With systemd, services start in parallel.
10849 Needless to say, the method can have an impact on system startup
10850 performance.
10851 </para>
10852
10853 <para>
10813 If you want to use SysVinit, you do 10854 If you want to use SysVinit, you do
10814 not have to do anything. 10855 not have to do anything.
10815 But, if you want to use systemd, you must 10856 But, if you want to use systemd, you must