commit 4fbe3cf623b31a8ae99df53caecafddb9d5bf455
Author: Stephen Wadeley <swadeley(a)redhat.com>
Date: Wed Oct 30 20:55:42 2013 +0100
Fixing links and titles to use title case
en-US/Configuring_NTP_Using_ntpd.xml
en-US/Configuring_NTP_Using_ntpd.xml | 15 +++++++--------
1 files changed, 7 insertions(+), 8 deletions(-)
---
diff --git a/en-US/Configuring_NTP_Using_ntpd.xml b/en-US/Configuring_NTP_Using_ntpd.xml
index 287837c..457a9bc 100644
--- a/en-US/Configuring_NTP_Using_ntpd.xml
+++ b/en-US/Configuring_NTP_Using_ntpd.xml
@@ -16,7 +16,6 @@
<para>
Accurate time keeping is important for a number of reasons in IT. In networking for
example, accurate time stamps in packets and logs are required. Logs are used to
investigate service and security issues and so timestamps made on different systems must
be made by synchronized clocks to be of real value. As systems and networks become
increasingly faster, there is a corresponding need for clocks with greater accuracy and
resolution. In some countries there are legal obligations to keep accurately synchronized
clocks. Please see <citetitle
pubwork="webpage">www.ntp.org</citetitle> for more information. In
Linux systems, <systemitem class="protocol">NTP</systemitem> is
implemented by a daemon running in user space. The default <systemitem
class="protocol">NTP</systemitem> user space daemon in &MAJOROSVER;
is <systemitem class="service">chronyd</systemitem>. It must be
disabled if you want to use the <systemitem
class="service">ntpd</systemitem> daemon. See <xref linkend=
"ch-Configuring_NTP_Using_the_chrony_Suite" /> for information on
<application>chrony</application>.
</para>
-
<para>
The user space daemon updates the system clock, which is a software clock running
in the kernel. Linux uses a software clock as its system clock for better resolution than
the typical embedded hardware clock referred to as the <quote><firstterm>Real
Time Clock</firstterm></quote> <acronym>(RTC)</acronym>. See the
<filename>rtc(4)</filename> and <filename>hwclock(8)</filename>
man pages for information on hardware clocks. The system clock can keep time by using
various clock sources. Usually, the <firstterm>Time Stamp Counter</firstterm>
(<acronym>TSC</acronym>) is used. The TSC is a CPU register which counts the
number of cycles since it was last reset. It is very fast, has a high resolution, and
there are no interrupts. On system start, the system clock reads the time and date from
the RTC. The time kept by the RTC will drift away from actual time by up to 5 minutes per
month due to temperature variations. Hence the need for the system clock to be constantly
synchroni
zed with external time references and to update the RTC on system shut down. When the
system clock is being synchronized by <systemitem
class="service">ntpd</systemitem>, the kernel will in turn update the
RTC every 11 minutes automatically.
</para>
@@ -140,7 +139,7 @@
</section>
<section id="s1-Understanding_the_drift_file">
- <title>Understanding The Drift File</title>
+ <title>Understanding the Drift File</title>
<para>
The drift file is used to store the frequency offset between the system clock running
at its nominal frequency and the frequency required to remain in synchronization with UTC.
If present, the value contained in the drift file is read at system start and used to
correct the clock source. Use of the drift file reduces the time required to achieve a
stable and accurate time. The value is calculated, and the drift file replaced, once per
hour by <systemitem class="daemon">ntpd</systemitem>. The drift file
is replaced, rather than just updated, and for this reason the drift file must be in a
directory for which the <systemitem class="daemon">ntpd</systemitem>
has write permissions.
</para>
@@ -151,7 +150,7 @@
<title>UTC, Timezones, and DST</title>
<para>
- As <systemitem class="protocol">NTP</systemitem> is entirely
in UTC (Universal Time, Coordinated), Timezones and DST (Daylight Saving Time) are applied
locally by the system. The file <filename>/etc/localtime</filename> is a copy
of, or symlink to, a zone information file from
<filename>/usr/share/zoneinfo</filename>. The RTC may be in localtime or in
UTC, as specified by the 3rd line of <filename>/etc/adjtime</filename>, which
will be one of LOCAL or UTC to indicate how the RTC clock has been set. Users can easily
change this setting using the checkbox <guilabel>System Clock Uses
UTC</guilabel> in the <application>Date and Time</application> graphical
configuration tool. See <xref linkend="ch-Configuring_the_Date_and_Time"
/> for information on how to use that tool. Running the RTC in UTC is recommended to
avoid various problems when daylight saving time is changed.
+ As <systemitem class="protocol">NTP</systemitem> is entirely in
UTC (Universal Time, Coordinated), Timezones and DST (Daylight Saving Time) are applied
locally by the system. The file <filename>/etc/localtime</filename> is a copy
of, or symlink to, a zone information file from
<filename>/usr/share/zoneinfo</filename>. The RTC may be in localtime or in
UTC, as specified by the 3rd line of <filename>/etc/adjtime</filename>, which
will be one of LOCAL or UTC to indicate how the RTC clock has been set. Users can easily
change this setting using the checkbox <guilabel>System Clock Uses
UTC</guilabel> in the <application>Date and Time</application> graphical
configuration tool. See <xref linkend="ch-Configuring_the_Date_and_Time"
/> for information on how to use that tool. Running the RTC in UTC is recommended to
avoid various problems when daylight saving time is changed.
</para>
<para>
The operation of <systemitem class="service">ntpd</systemitem>
is explained in more detail in the man page <filename>ntpd(8)</filename>. The
resources section lists useful sources of information. See <xref
linkend="s1-ntpd_additional-resources"/>.
@@ -304,7 +303,7 @@ To check the status of <systemitem
class="daemon">chronyd</systemitem>, issue th
<section id="s1-Checking_if_ntpd_is_installed">
- <title>Checking If the NTP Daemon Is Installed</title>
+ <title>Checking if the NTP Daemon is Installed</title>
<para>
To check if <systemitem class="service">ntpd</systemitem>
is installed, enter the following command as root:
<screen>~]# <command>yum install ntp</command></screen>
@@ -339,7 +338,7 @@ unsynchronised
time server re-starting
polling server every 64 s</screen>
<screen>~]$ <command>ntpstat</command>
-synchronised to NTP server (10.5.26.10) at stratum 2
+synchronised to NTP server (10.5.26.10) at stratum 2
time correct to within 52 ms
polling server every 1024 s</screen>
</para>
@@ -369,7 +368,7 @@ synchronised to NTP server (10.5.26.10) at stratum 2
<section id="s2-Change_the_firewall_settings">
- <title>Change The Firewall Settings</title>
+ <title>Change the Firewall Settings</title>
<para>
To immediately change the current firewall settings, ensure the current view is set
to <guilabel>Runtime Configuration</guilabel>. Alternatively, to edit the
settings to be applied at the next system start, or firewall reload, select
<guilabel>Permanent Configuration</guilabel> from the drop-down list.
</para>
@@ -383,7 +382,7 @@ synchronised to NTP server (10.5.26.10) at stratum 2
</section>
<section id="s2-Open_Ports_in_the_firewall_for_ntp_packets">
- <title>Open Ports In The Firewall For NTP Packets</title>
+ <title>Open Ports in the Firewall for NTP Packets</title>
<para>
To permit traffic through the firewall to a certain port, start the
<application>firewall-config</application> tool and select the network zone
whose settings you want to change. Select the <guilabel>Ports</guilabel> tab
and the click the <guibutton>Add</guibutton> button on the right hand side.
The <guilabel>Port and Protocol</guilabel> window opens.
</para>
@@ -543,7 +542,7 @@ synchronised to NTP server (10.5.26.10) at stratum 2
</para>
<para>
- This command configures a system to act as an <systemitem
class="protocol">NTP</systemitem> broadcast server. The address used
must be a broadcast or a multicast address. Broadcast address implies the <systemitem
class="protocol">IPv4</systemitem> address <systemitem
class="ipaddress">255.255.255.255</systemitem>. By default, routers do
not pass broadcast messages. The multicast address can be an <systemitem
class="protocol">IPv4</systemitem> Class D address, or an
<systemitem class="protocol">IPv6</systemitem> address. The IANA has
assigned <systemitem class="protocol">IPv4</systemitem> multicast
address <systemitem class="ipaddress">224.0.1.1</systemitem> and
<systemitem class="protocol">IPv6</systemitem> address
<systemitem class="ipaddress">FF05::101</systemitem> (site local) to
<systemitem class="protocol">NTP</systemitem>. Administratively
scoped<systemitem class="protocol">IPv4</systemitem> multicast
addresses can also be used, as described in <ulink url="
http://www.rfc-editor.org/info/rfc2365"><citetitle
pubwork="webpage">RFC 2365 Administratively Scoped IP
Multicast</citetitle></ulink>.
+ This command configures a system to act as an <systemitem
class="protocol">NTP</systemitem> broadcast server. The address used
must be a broadcast or a multicast address. Broadcast address implies the <systemitem
class="protocol">IPv4</systemitem> address <systemitem
class="ipaddress">255.255.255.255</systemitem>. By default, routers do
not pass broadcast messages. The multicast address can be an <systemitem
class="protocol">IPv4</systemitem> Class D address, or an
<systemitem class="protocol">IPv6</systemitem> address. The IANA has
assigned <systemitem class="protocol">IPv4</systemitem> multicast
address <systemitem class="ipaddress">224.0.1.1</systemitem> and
<systemitem class="protocol">IPv6</systemitem> address
<systemitem class="ipaddress">FF05::101</systemitem> (site local) to
<systemitem class="protocol">NTP</systemitem>. Administratively
scoped<systemitem class="protocol">IPv4</systemitem> multicast
addresses can also be used, as described in <ulink url="h
ttp://www.rfc-editor.org/info/rfc2365"><citetitle
pubwork="webpage">RFC 2365 Administratively Scoped IP
Multicast</citetitle></ulink>.
</para>
</section>