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git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/merge@11076 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
176 lines
6.6 KiB
XML
176 lines
6.6 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="ch-scripts-systemd-custom" revision="systemd">
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<?dbhtml filename="systemd-custom.html"?>
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<title>Systemd Usage and Configuration</title>
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<indexterm zone="ch-scripts-systemd-custom">
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<primary sortas="e-Systemd">Systemd Customization</primary>
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</indexterm>
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<sect2>
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<title>Basic Configuration</title>
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<para>The <filename>/etc/systemd/system.conf</filename> file contains a set
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of options to control basic systemd operations. The default file has all
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entries commented out with the default settings indicated. This file is
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where the log level may be changed as well as some basic logging settings.
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See <filename>systemd-system.conf(5)</filename> manual page for details on
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each configuration option.</para>
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</sect2>
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<sect2>
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<title>Disabling Screen Clearing at Boot Time</title>
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<para>The normal behavior for systemd is to clear the screen at
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the end of the boot sequence. If desired, this behavior may be
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changed by running the following command:</para>
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<screen role="nodump"><userinput>mkdir -pv /etc/systemd/system/getty@tty1.service.d
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cat > /etc/systemd/system/getty@tty1.service.d/noclear.conf << EOF
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<literal>[Service]
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TTYVTDisallocate=no</literal>
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EOF</userinput></screen>
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<para>The boot messages can always be revied by using the
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<userinput>journalctl -b</userinput> command as the root user.</para>
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</sect2>
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<sect2>
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<title>Disabling tmpfs for /tmp</title>
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<para>By default, <filename class="directory">/tmp</filename> is created as
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a tmpfs. If this is not desired, it can be overridden by the following:</para>
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<screen role="nodump"><userinput>ln -sfv /dev/null /etc/systemd/system/tmp.mount</userinput></screen>
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<para>This is not necessary if there is a separate partition for
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<filename class="directory">/tmp</filename> specified in
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<filename>/etc/fstab</filename>.</para>
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</sect2>
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<sect2>
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<title>Configuring Automatic File Creation and Deletion</title>
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<para>There are several services that create or delete files or
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directories:</para>
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<itemizedlist>
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<listitem><para>systemd-tmpfiles-clean.service</para></listitem>
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<listitem><para>systemd-tmpfiles-setup-dev.service</para></listitem>
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<listitem><para>systemd-tmpfiles-setup.service</para></listitem>
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</itemizedlist>
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<para>The system location for the configuration files is
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<filename>/usr/lib/tmpfiles.d/*.conf</filename>. The local
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configuration files are in
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<filename class="directory">/etc/tmpfiles.d</filename>. Files in
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<filename class="directory">/etc/tmpfiles.d</filename> override
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files with the same name in
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<filename class="directory">/usr/lib/tmpfiles.d</filename>. See
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<filename>tmpfiles.d(5)</filename> manual page for file format
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details.</para>
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</sect2>
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<sect2>
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<title>Overriding Default Services Behavior</title>
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<para>A systemd service contents can be overriden by creating a directory
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and a configuration file in <filename
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class="directory">/etc/systemd/system</filename>. For example:</para>
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<screen role="nodump"><userinput>mkdir -pv /etc/systemd/system/foobar.service.d
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cat > /etc/systemd/system/foobar.service.d/foobar.conf << EOF
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<literal>[Service]
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Restart=always
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RestartSec=30</literal>
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EOF</userinput></screen>
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<para>See <filename>systemd.unit(5)</filename> manual page for more
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information. After creating the configuration file, run
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<userinput>systemctl daemon-reload</userinput> and <userinput>systemctl
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restart foobar</userinput> to activate the changes to a service.</para>
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</sect2>
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<sect2>
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<title>Debugging the Boot Sequence</title>
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<para>Rather than plain shell scripts used in SysVinit or BSD style init
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systems, systemd uses a unified format for different type of startup
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files (or units). The command <command>systemctl</command> is used to
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enable, disable, controll state, and obtain status of unit files. Here
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are some examples of frequently used commands:</para>
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<itemizedlist>
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<listitem>
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<para><command>systemctl list-units -t <replaceable><service></replaceable> [--all]</command>:
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lists loaded unit files of type service.</para>
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</listitem>
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<listitem>
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<para><command>systemctl list-units -t <replaceable><target></replaceable> [--all]</command>:
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lists loaded unit files of type target.</para>
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</listitem>
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<listitem>
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<para><command>systemctl show -p Wants <replaceable><multi-user.target></replaceable></command>:
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shows all units that depend on the multi-user target. Targets are
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special unit files that are anogalous to runlevels under
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SysVinit.</para>
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</listitem>
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<listitem>
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<para><command>systemctl status <replaceable><servicename.service></replaceable></command>:
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shows the status of the servicename service. The .service extension
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can be omitted if there are no other unit files with the same name,
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such as .socket files (which create a listening socket that provides
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similar functionality to inetd/xinetd).</para>
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</listitem>
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</itemizedlist>
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</sect2>
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<sect2>
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<title>Working with the Systemd Journal</title>
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<para>Logging on a system booted with systemd is handled by
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systemd-journald (default), rather than a typical unix syslog daemon.
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systemd-journald write log entries to a binary file format, rather than
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a plain text log file. To assist with parsing the file, the command
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<command>journalctl</command> is provided. Here are some examples of
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frequently used commands:</para>
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<itemizedlist>
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<listitem>
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<para><command>journalctl -r</command>: shows all contents of the
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journal in reverse chronological order.</para>
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</listitem>
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<listitem>
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<para><command>journalctl -u <replaceable>UNIT</replaceable></command>:
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shows the journal entries associated with the specified UNIT
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file.</para>
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</listitem>
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<listitem>
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<para><command>journalctl -b[=ID] -r</command>: shows the journal
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entries since last successfull boot (or for boot ID) in reverse
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chronological order.</para>
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</listitem>
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<listitem>
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<para><command>journalctl -f</command>: povides functionality similar
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to tail -f (follow).</para>
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</listitem>
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</itemizedlist>
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</sect2>
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</sect1>
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