| 1 | <?xml version="1.0" encoding="UTF-8"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 |
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| 7 | <!ENTITY ntp-download-http "https://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-&ntp-version;.tar.gz">
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| 8 | <!ENTITY ntp-download-ftp " ">
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| 9 | <!ENTITY ntp-md5sum "a15558df580bd1b955a105a8b91c078f">
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| 10 | <!ENTITY ntp-size "6.8 MB">
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| 11 | <!ENTITY ntp-buildsize "99 MB (with tests)">
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| 12 | <!ENTITY ntp-time "0.8 SBU (With tests; both using parallelism=4)">
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| 13 | ]>
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| 14 |
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| 15 | <sect1 id="ntp" xreflabel="ntp-&ntp-version;">
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| 16 | <?dbhtml filename="ntp.html"?>
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| 17 |
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| 18 |
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| 19 | <title>ntp-&ntp-version;</title>
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| 20 |
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| 21 | <indexterm zone="ntp">
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| 22 | <primary sortas="a-ntp">ntp</primary>
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| 23 | </indexterm>
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| 24 |
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| 25 | <sect2 role="package">
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| 26 | <title>Introduction to ntp</title>
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| 27 |
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| 28 | <para>
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| 29 | The <application>ntp</application> package contains a client and server
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| 30 | to keep the time synchronized between various computers over
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| 31 | a network. This package is the official reference implementation of the
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| 32 | NTP protocol.
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| 33 | </para>
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| 34 |
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| 35 | &lfs121_checked;
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| 36 |
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| 37 | <bridgehead renderas="sect3">Package Information</bridgehead>
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| 38 | <itemizedlist spacing="compact">
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| 39 | <listitem>
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| 40 | <para>
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| 41 | Download (HTTP): <ulink url="&ntp-download-http;"/>
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| 42 | </para>
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| 43 | </listitem>
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| 44 | <listitem>
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| 45 | <para>
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| 46 | Download (FTP): <ulink url="&ntp-download-ftp;"/>
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| 47 | </para>
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| 48 | </listitem>
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| 49 | <listitem>
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| 50 | <para>
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| 51 | Download MD5 sum: &ntp-md5sum;
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| 52 | </para>
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| 53 | </listitem>
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| 54 | <listitem>
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| 55 | <para>
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| 56 | Download size: &ntp-size;
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| 57 | </para>
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| 58 | </listitem>
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| 59 | <listitem>
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| 60 | <para>
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| 61 | Estimated disk space required: &ntp-buildsize;
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| 62 | </para>
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| 63 | </listitem>
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| 64 | <listitem>
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| 65 | <para>
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| 66 | Estimated build time: &ntp-time;
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| 67 | </para>
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| 68 | </listitem>
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| 69 | </itemizedlist>
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| 70 |
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| 71 | <bridgehead renderas="sect3">ntp Dependencies</bridgehead>
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| 72 |
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| 73 | <bridgehead renderas="sect4">Required</bridgehead>
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| 74 | <para role="required">
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| 75 | <xref linkend="perl-io-socket-ssl"/>
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| 76 | </para>
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| 77 |
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| 78 | <!-- Tested 4.2.8p11 with neither wget nor lynx on system: Not required.
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| 79 | <bridgehead renderas="sect4">Recommended</bridgehead>
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| 80 | <para role="recommended">
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| 81 | <xref role="runtime" linkend="wget"/> (runtime, for
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| 82 | <command>update-leap</command>)
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| 83 | <!- - The download code for update-leap uses the File::Fetch perl module,
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| 84 | which may use wget, or lynx, or some core perl modules, so maybe move
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| 85 | to optional - ->
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| 86 | </para>
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| 87 | -->
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| 88 | <bridgehead renderas="sect4">Optional</bridgehead>
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| 89 | <para role="optional">
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| 90 | <xref linkend="libcap-pam"/>,
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| 91 | <xref linkend="libevent"/>,
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| 92 | <ulink url="https://www.thrysoee.dk/editline/">libedit</ulink>, and
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| 93 | <ulink url="https://www.gnu.org/software/autogen/">libopts from AutoGen</ulink>
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| 94 | </para>
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| 95 |
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| 96 | <para condition="html" role="usernotes">Editor Notes:
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| 97 | <ulink url="&blfs-wiki;/ntp"/></para>
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| 98 |
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| 99 | </sect2>
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| 100 |
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| 101 | <sect2 role="installation">
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| 102 | <title>Installation of ntp</title>
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| 103 |
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| 104 | <para>
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| 105 | There should be a dedicated user and group to take control
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| 106 | of the <command>ntpd</command> daemon after it is
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| 107 | started. Issue the following commands as the
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| 108 | <systemitem class="username">root</systemitem> user:
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| 109 | </para>
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| 110 |
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| 111 | <screen role="root"><userinput>groupadd -g 87 ntp &&
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| 112 | useradd -c "Network Time Protocol" -d /var/lib/ntp -u 87 \
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| 113 | -g ntp -s /bin/false ntp</userinput></screen>
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| 114 |
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| 115 | <!-- At least one of the issues has been reported upstream. The next para
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| 116 | is valid for 4.8.2p10.
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| 117 |
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| 118 | Leap secongs have been deprecated as of November 2022.
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| 119 | https://en.wikipedia.org/wiki/Leap_second
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| 120 |
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| 121 | <para>
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| 122 | The <command>update-leap</command> command needs to be fixed in order
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| 123 | to run properly:
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| 124 | </para>
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| 125 |
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| 126 | <screen><userinput>sed -e 's/"(\\S+)"/"?([^\\s"]+)"?/' \
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| 127 | -i scripts/update-leap/update-leap.in</userinput></screen>
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| 128 | -->
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| 129 |
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| 130 | <para>
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| 131 | Install <application>ntp</application> by running
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| 132 | the following commands:
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| 133 | </para>
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| 134 |
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| 135 | <screen><userinput>./configure --prefix=/usr \
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| 136 | --bindir=/usr/sbin \
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| 137 | --sysconfdir=/etc \
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| 138 | --enable-linuxcaps \
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| 139 | --with-lineeditlibs=readline \
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| 140 | --docdir=/usr/share/doc/ntp-&ntp-version; &&
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| 141 | make</userinput></screen>
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| 142 |
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| 143 | <para>
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| 144 | To test the results, issue: <command>make check</command>.
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| 145 | </para>
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| 146 |
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| 147 | <para>
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| 148 | Now, as the <systemitem class="username">root</systemitem> user:
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| 149 | </para>
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| 150 |
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| 151 | <screen role="root"><userinput>make install &&
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| 152 | install -v -o ntp -g ntp -d /var/lib/ntp</userinput></screen>
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| 153 |
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| 154 | </sect2>
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| 155 |
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| 156 | <sect2 role="commands">
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| 157 | <title>Command Explanations</title>
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| 158 |
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| 159 | <para>
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| 160 | <parameter>--bindir=/usr/sbin</parameter>: This parameter places
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| 161 | the administrative programs in <filename
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| 162 | class="directory">/usr/sbin</filename>.
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| 163 | </para>
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| 164 |
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| 165 | <para>
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| 166 | <parameter>--enable-linuxcaps</parameter>: ntpd is run as user
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| 167 | ntp, so use Linux capabilities for non-root clock control.
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| 168 | </para>
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| 169 |
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| 170 | <para>
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| 171 | <parameter>--with-lineeditlibs=readline</parameter>: This switch
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| 172 | enables <application>Readline</application> support for
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| 173 | <command>ntpdc</command> and <command>ntpq</command> programs. If omitted,
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| 174 | <application>libedit</application> will be used if installed, otherwise no
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| 175 | readline capabilities will be compiled.
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| 176 | </para>
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| 177 |
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| 178 | </sect2>
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| 179 |
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| 180 | <sect2 role="configuration">
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| 181 | <title>Configuring ntp</title>
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| 182 |
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| 183 | <sect3 id="ntp-config">
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| 184 | <title>Config Files</title>
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| 185 |
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| 186 | <para>
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| 187 | <filename>/etc/ntp.conf</filename>
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| 188 | </para>
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| 189 |
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| 190 | <indexterm zone="ntp ntp-config">
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| 191 | <primary sortas="e-etc-ntp.conf">/etc/ntp.conf</primary>
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| 192 | </indexterm>
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| 193 |
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| 194 | </sect3>
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| 195 |
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| 196 | <sect3>
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| 197 | <title>Configuration Information</title>
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| 198 |
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| 199 | <para>
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| 200 | The following configuration file first defines various ntp
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| 201 | servers with open access from different continents. Second, it
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| 202 | creates a drift file where <command>ntpd</command> stores the
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| 203 | frequency offset and a pid file to store the
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| 204 | <command>ntpd</command> process ID. <!--Third, it defines the location
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| 205 | for the leap-second definition file
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| 206 | <filename>/etc/ntp.leapseconds</filename>, that the
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| 207 | <command>update-leap</command> script checks and updates, when
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| 208 | necessary. This script can be run as a cron job and the
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| 209 | <application>ntp</application> developers recommend a frequency of
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| 210 | about three weeks for the updates.--> Since the documentation included
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| 211 | with the package is sparse, visit the ntp website at
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| 212 | <ulink url="https://www.ntp.org/"/> and
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| 213 | <ulink url="https://www.ntppool.org/"/> for more information.
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| 214 | </para>
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| 215 |
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| 216 | <screen role="root"><userinput>cat > /etc/ntp.conf << "EOF"
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| 217 | <literal># Asia
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| 218 | server 0.asia.pool.ntp.org
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| 219 |
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| 220 | # Australia
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| 221 | server 0.oceania.pool.ntp.org
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| 222 |
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| 223 | # Europe
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| 224 | server 0.europe.pool.ntp.org
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| 225 |
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| 226 | # North America
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| 227 | server 0.north-america.pool.ntp.org
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| 228 |
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| 229 | # South America
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| 230 | server 2.south-america.pool.ntp.org
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| 231 |
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| 232 | driftfile /var/lib/ntp/ntp.drift
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| 233 | pidfile /run/ntpd.pid</literal>
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| 234 | EOF</userinput></screen>
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| 235 |
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| 236 | <para>
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| 237 | You may wish to add a <quote>Security session</quote>. For
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| 238 | explanations, see <ulink url=
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| 239 | "https://www.eecis.udel.edu/~mills/ntp/html/accopt.html#restrict"/>.
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| 240 | </para>
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| 241 |
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| 242 | <screen role="root"><userinput>cat >> /etc/ntp.conf << "EOF"
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| 243 | <literal># Security session
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| 244 | restrict default limited kod nomodify notrap nopeer noquery
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| 245 | restrict -6 default limited kod nomodify notrap nopeer noquery
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| 246 |
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| 247 | restrict 127.0.0.1
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| 248 | restrict ::1</literal>
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| 249 | EOF</userinput></screen>
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| 250 |
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| 251 | </sect3>
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| 252 |
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| 253 | <sect3 id="ntp-init">
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| 254 | <title>Synchronizing the Time</title>
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| 255 |
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| 256 | <para>
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| 257 | There are two options. Option one is to run <command>ntpd</command>
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| 258 | continuously and allow it to synchronize the time in a gradual manner.
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| 259 | The other option is to run <command>ntpd</command> periodically (using
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| 260 | cron) and update the time each time <command>ntpd</command> is
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| 261 | scheduled.
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| 262 | </para>
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| 263 |
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| 264 | <para>
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| 265 | If you choose Option one, then install the
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| 266 | <phrase revision="sysv"><filename>/etc/rc.d/init.d/ntp</filename>
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| 267 | init script</phrase>
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| 268 | <phrase revision="systemd"><filename>ntpd.service</filename>
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| 269 | unit</phrase>
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| 270 | included in the
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| 271 | <xref linkend="bootscripts" revision="sysv"/>
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| 272 | <xref linkend="systemd-units" revision="systemd"/> package.
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| 273 | </para>
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| 274 |
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| 275 | <indexterm zone="ntp ntp-init" revision="sysv">
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| 276 | <primary sortas="f-ntp">ntp</primary>
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| 277 | </indexterm>
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| 278 |
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| 279 | <indexterm zone="ntp ntp-init" revision="systemd">
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| 280 | <primary sortas="f-ntpd">ntpd.service</primary>
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| 281 | </indexterm>
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| 282 |
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| 283 | <screen role="root"><userinput>make install-ntpd</userinput></screen>
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| 284 |
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| 285 | <para>
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| 286 | If you prefer to run <command>ntpd</command> periodically, add the
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| 287 | following command to <systemitem class="username">root</systemitem>'s
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| 288 | <filename>crontab</filename>:
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| 289 | </para>
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| 290 |
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| 291 | <screen><literal>ntpd -q</literal></screen>
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| 292 |
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| 293 | <para revision="sysv">
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| 294 | Execute the following command if you would like to set the hardware
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| 295 | clock to the current system time at shutdown and reboot:
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| 296 | </para>
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| 297 |
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| 298 | <screen role="root" revision="sysv"><userinput>ln -v -sf ../init.d/setclock /etc/rc.d/rc0.d/K46setclock &&
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| 299 | ln -v -sf ../init.d/setclock /etc/rc.d/rc6.d/K46setclock</userinput></screen>
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| 300 |
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| 301 | <para revision="sysv">
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| 302 | The other way around is already set up by LFS.
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| 303 | </para>
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| 304 |
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| 305 | </sect3>
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| 306 |
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| 307 | </sect2>
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| 308 |
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| 309 | <sect2 role="content">
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| 310 | <title>Contents</title>
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| 311 |
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| 312 | <segmentedlist>
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| 313 | <segtitle>Installed Programs</segtitle>
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| 314 | <segtitle>Installed Libraries</segtitle>
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| 315 | <segtitle>Installed Directories</segtitle>
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| 316 |
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| 317 | <seglistitem>
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| 318 | <seg>calc_tickadj, ntp-keygen, ntp-wait, ntpd, ntpdate, ntpdc, ntpq,
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| 319 | ntptime, ntptrace, sntp, tickadj, and update-leap</seg>
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| 320 | <seg>None</seg>
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| 321 | <seg>/usr/share/ntp,
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| 322 | /usr/share/doc/ntp-4.2.8 and
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| 323 | /var/lib/ntp</seg>
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| 324 | </seglistitem>
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| 325 | </segmentedlist>
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| 326 |
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| 327 | <variablelist>
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| 328 | <bridgehead renderas="sect3">Short Descriptions</bridgehead>
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| 329 | <?dbfo list-presentation="list"?>
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| 330 | <?dbhtml list-presentation="table"?>
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| 331 |
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| 332 | <varlistentry id="calc_tickadj">
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| 333 | <term><command>calc_tickadj</command></term>
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| 334 | <listitem>
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| 335 | <para>
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| 336 | calculates optimal value for tick given ntp drift file
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| 337 | </para>
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| 338 | <indexterm zone="ntp calc_tickadj">
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| 339 | <primary sortas="b-calc_tickadj">calc_tickadj</primary>
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| 340 | </indexterm>
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| 341 | </listitem>
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| 342 | </varlistentry>
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| 343 |
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| 344 | <varlistentry id="ntp-keygen">
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| 345 | <term><command>ntp-keygen</command></term>
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| 346 | <listitem>
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| 347 | <para>
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| 348 | generates cryptographic data files used by the NTPv4 authentication
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| 349 | and identification schemes
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| 350 | </para>
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| 351 | <indexterm zone="ntp ntp-keygen">
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| 352 | <primary sortas="b-ntp-keygen">ntp-keygen</primary>
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| 353 | </indexterm>
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| 354 | </listitem>
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| 355 | </varlistentry>
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| 356 |
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| 357 | <varlistentry id="ntp-wait">
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| 358 | <term><command>ntp-wait</command></term>
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| 359 | <listitem>
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| 360 | <para>
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| 361 | is useful at boot time, to delay the boot sequence until
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| 362 | <command>ntpd</command> has set the time
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| 363 | </para>
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| 364 | <indexterm zone="ntp ntp-wait">
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| 365 | <primary sortas="b-ntp-wait">ntp-wait</primary>
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| 366 | </indexterm>
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| 367 | </listitem>
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| 368 | </varlistentry>
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| 369 |
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| 370 | <varlistentry id="ntpd">
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| 371 | <term><command>ntpd</command></term>
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| 372 | <listitem>
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| 373 | <para>
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| 374 | is a ntp daemon that runs in the background and keeps
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| 375 | the date and time synchronized based on response from configured
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| 376 | ntp servers. It also functions as a ntp server
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| 377 | </para>
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| 378 | <indexterm zone="ntp ntpd">
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| 379 | <primary sortas="b-ntpd">ntpd</primary>
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| 380 | </indexterm>
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|---|
| 381 | </listitem>
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|---|
| 382 | </varlistentry>
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|---|
| 383 |
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| 384 | <varlistentry id="ntpdate">
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|---|
| 385 | <term><command>ntpdate</command></term>
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|---|
| 386 | <listitem>
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| 387 | <para>
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| 388 | is a client program that sets the date and time based on
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|---|
| 389 | the response from an ntp server. This command is deprecated
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| 390 | </para>
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|---|
| 391 | <indexterm zone="ntp ntpdate">
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|---|
| 392 | <primary sortas="b-ntpdate">ntpdate</primary>
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| 393 | </indexterm>
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|---|
| 394 | </listitem>
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|---|
| 395 | </varlistentry>
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|---|
| 396 |
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| 397 | <varlistentry id="ntpdc">
|
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| 398 | <term><command>ntpdc</command></term>
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|---|
| 399 | <listitem>
|
|---|
| 400 | <para>
|
|---|
| 401 | is used to query the ntp daemon about its current state
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|---|
| 402 | and to request changes in that state
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| 403 | </para>
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| 404 | <indexterm zone="ntp ntpdc">
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| 405 | <primary sortas="b-ntpdc">ntpdc</primary>
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| 406 | </indexterm>
|
|---|
| 407 | </listitem>
|
|---|
| 408 | </varlistentry>
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|---|
| 409 |
|
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| 410 | <varlistentry id="ntpq">
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|---|
| 411 | <term><command>ntpq</command></term>
|
|---|
| 412 | <listitem>
|
|---|
| 413 | <para>
|
|---|
| 414 | is a utility program used to monitor <command>ntpd</command>
|
|---|
| 415 | operations and determine performance
|
|---|
| 416 | </para>
|
|---|
| 417 | <indexterm zone="ntp ntpq">
|
|---|
| 418 | <primary sortas="b-ntpq">ntpq</primary>
|
|---|
| 419 | </indexterm>
|
|---|
| 420 | </listitem>
|
|---|
| 421 | </varlistentry>
|
|---|
| 422 |
|
|---|
| 423 | <varlistentry id="ntptime">
|
|---|
| 424 | <term><command>ntptime</command></term>
|
|---|
| 425 | <listitem>
|
|---|
| 426 | <para>
|
|---|
| 427 | reads and displays time-related kernel variables
|
|---|
| 428 | </para>
|
|---|
| 429 | <indexterm zone="ntp ntptime">
|
|---|
| 430 | <primary sortas="b-ntptime">ntptime</primary>
|
|---|
| 431 | </indexterm>
|
|---|
| 432 | </listitem>
|
|---|
| 433 | </varlistentry>
|
|---|
| 434 |
|
|---|
| 435 | <varlistentry id="ntptrace">
|
|---|
| 436 | <term><command>ntptrace</command></term>
|
|---|
| 437 | <listitem>
|
|---|
| 438 | <para>
|
|---|
| 439 | traces a chain of ntp servers back to the primary source
|
|---|
| 440 | </para>
|
|---|
| 441 | <indexterm zone="ntp ntptrace">
|
|---|
| 442 | <primary sortas="b-ntptrace">ntptrace</primary>
|
|---|
| 443 | </indexterm>
|
|---|
| 444 | </listitem>
|
|---|
| 445 | </varlistentry>
|
|---|
| 446 |
|
|---|
| 447 | <varlistentry id="sntp">
|
|---|
| 448 | <term><command>sntp</command></term>
|
|---|
| 449 | <listitem>
|
|---|
| 450 | <para>
|
|---|
| 451 | is a Simple Network Time Protocol (SNTP) client
|
|---|
| 452 | </para>
|
|---|
| 453 | <indexterm zone="ntp sntp">
|
|---|
| 454 | <primary sortas="b-sntp">sntp</primary>
|
|---|
| 455 | </indexterm>
|
|---|
| 456 | </listitem>
|
|---|
| 457 | </varlistentry>
|
|---|
| 458 |
|
|---|
| 459 | <varlistentry id="tickadj">
|
|---|
| 460 | <term><command>tickadj</command></term>
|
|---|
| 461 | <listitem>
|
|---|
| 462 | <para>
|
|---|
| 463 | reads, and optionally modifies, several timekeeping-related
|
|---|
| 464 | variables in older kernels that do not have support for precision
|
|---|
| 465 | timekeeping
|
|---|
| 466 | </para>
|
|---|
| 467 | <indexterm zone="ntp tickadj">
|
|---|
| 468 | <primary sortas="b-tickadj">tickadj</primary>
|
|---|
| 469 | </indexterm>
|
|---|
| 470 | </listitem>
|
|---|
| 471 | </varlistentry>
|
|---|
| 472 |
|
|---|
| 473 | <varlistentry id="update-leap">
|
|---|
| 474 | <term><command>update-leap</command></term>
|
|---|
| 475 | <listitem>
|
|---|
| 476 | <para>
|
|---|
| 477 | is a script to verify and, if necessary, update the leap-second
|
|---|
| 478 | definition file.
|
|---|
| 479 |
|
|---|
| 480 | <note>
|
|---|
| 481 | <para>
|
|---|
| 482 | In November 2022, at the 27th General Conference on Weights and
|
|---|
| 483 | Measures, it was decided to abandon the leap second. In addition
|
|---|
| 484 | this script hardcodes a URL for an update file that no longer
|
|---|
| 485 | exists. The last time a leap second was declared was January 2017.
|
|---|
| 486 | This script will probably be removed in a future release.
|
|---|
| 487 | </para>
|
|---|
| 488 | </note>
|
|---|
| 489 | </para>
|
|---|
| 490 | <indexterm zone="ntp update-leap">
|
|---|
| 491 | <primary sortas="b-update-leap">update-leap</primary>
|
|---|
| 492 | </indexterm>
|
|---|
| 493 | </listitem>
|
|---|
| 494 | </varlistentry>
|
|---|
| 495 |
|
|---|
| 496 | </variablelist>
|
|---|
| 497 |
|
|---|
| 498 | </sect2>
|
|---|
| 499 |
|
|---|
| 500 | </sect1>
|
|---|
