commit f6d4f8067811a27b494333f5182b9dcc1a80a028
Author: Stephen Wadeley <swadeley(a)redhat.com>
Date: Thu Jul 31 09:53:51 2014 +0200
Add: Configure ntpdate Servers
en-US/Configuring_NTP_Using_ntpd.xml | 24 ++++++++++++++++++++++++
1 files changed, 24 insertions(+), 0 deletions(-)
---
diff --git a/en-US/Configuring_NTP_Using_ntpd.xml b/en-US/Configuring_NTP_Using_ntpd.xml
index 8b36ccd..e14ebdc 100644
--- a/en-US/Configuring_NTP_Using_ntpd.xml
+++ b/en-US/Configuring_NTP_Using_ntpd.xml
@@ -392,6 +392,30 @@ synchronised to NTP server (10.5.26.10) at stratum 2
</section>
+<section id="s1-Configure_ntpdate_Servers">
+ <title>Configure ntpdate Servers</title>
+ <para>
+ The purpose of the <systemitem
class="daemon">ntpdate</systemitem> service is to set the clock during
system boot. This was used previously to ensure that the services started after
<systemitem class="daemon">ntpdate</systemitem> would have the
correct time and not observe a jump in the clock. The use of <systemitem
class="daemon">ntpdate</systemitem> and the list of step-tickers is
considered deprecated and so Fedora uses the <option>-g</option> option to the
<command>ntpd</command> command and not <systemitem
class="daemon">ntpdate</systemitem> by default.
+ </para>
+ <para>
+ The <systemitem class="daemon">ntpdate</systemitem> service in
Fedora is mostly useful only when used alone without <systemitem
class="daemon">ntpd</systemitem>. With
<application>systemd</application>, which starts services in parallel,
enabling the <systemitem class="daemon">ntpdate</systemitem> service
will not ensure that other services started after it will have correct time unless they
specify an ordering dependency on <literal>time-sync.target</literal>, which
is provided by the <systemitem class="daemon">ntpdate</systemitem>
service. The <systemitem class="service">ntp-wait</systemitem>
service (in the <package>ntp-perl</package> subpackage) provides the
<literal>time-sync</literal> target for the <systemitem
class="daemon">ntpd</systemitem> service. In order to ensure a service
starts with correct time, add <literal>After=time-sync.target</literal> to the
service and enable one of the services which provide the target (<systemitem
class="daemon">ntpdate</systemi
tem> or <application>sntp</application>, or
<application>ntp-wait</application> if <systemitem
class="daemon">ntpd</systemitem> is enabled). Some services on Fedora
have the dependency included by default ( for example, <systemitem
class="daemon">dhcpd</systemitem>, <systemitem
class="daemon">dhcpd6</systemitem>, and <systemitem
class="daemon">crond</systemitem>).
+ </para>
+ <para>
+ To check if the <systemitem class="daemon">ntpdate</systemitem>
service is enabled to run at system start, issue the following command:
+ <screen>~]$ <command>systemctl status
ntpdate</command></screen>
+</para>
+<para>
+ To enable the service to run at system start, issue the following command as
<systemitem class="username">root</systemitem>:
+ <screen>~]# <command>systemctl enable
ntpdate</command></screen>
+</para>
+
+<para>
+ In Fedora the default <filename>/etc/ntp/step-tickers</filename> file
contains <literal>0.fedora.pool.ntp.org</literal>. To configure additional
<systemitem class="daemon">ntpdate</systemitem> servers, using a
text editor running as <systemitem
class="username">root</systemitem>, edit
<filename>/etc/ntp/step-tickers</filename>. The number of servers listed is
not very important as <systemitem
class="daemon">ntpdate</systemitem> will only use this to obtain the
date information once when the system is starting. If you have an internal time server
then use that host name for the first line. An additional host on the second line as a
backup is sensible. The selection of backup servers and whether the second host is
internal or external depends on your risk assessment. For example, what is the chance of
any problem affecting the first server also affecting the second server? Would
connectivity to an external server be more likely to be available than connectivity to
internal s
ervers in the event of a network failure disrupting access to the first server?
+</para>
+
+</section>
+
+
<section id="s1-Configure_NTP">
<title>Configure NTP</title>
<para>
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