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diff --git a/sag-0.6.1-www/sag-0.6.1.html/x2457.html b/sag-0.6.1-www/sag-0.6.1.html/x2457.html new file mode 100644 index 0000000..427c375 --- /dev/null +++ b/sag-0.6.1-www/sag-0.6.1.html/x2457.html @@ -0,0 +1,354 @@ +<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN"> +<HTML +><HEAD +><TITLE +>Showing and setting time</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet"><LINK +REL="HOME" +TITLE="The Linux System Administrators' Guide" +HREF="book1.html"><LINK +REL="UP" +TITLE="Keeping Time" +HREF="c2432.html"><LINK +REL="PREVIOUS" +TITLE="The hardware and software clocks" +HREF="x2451.html"><LINK +REL="NEXT" +TITLE="When the clock is wrong" +HREF="x2504.html"></HEAD +><BODY +BGCOLOR="#FFFFFF" +TEXT="#000000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>The Linux System Administrators' Guide</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x2451.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +>Chapter 11. Keeping Time</TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x2504.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECT1" +><H1 +CLASS="SECT1" +><A +NAME="AEN2457" +>Showing and setting time</A +></H1 +><P +> In the Debian system, the system time zone is determined + by the symbolic link <TT +CLASS="FILENAME" +>/etc/localtime</TT +>. + This link points at a time zone data file that describes + the local time zone. The time zone data files are stored in + <TT +CLASS="FILENAME" +>/usr/lib/zoneinfo</TT +>. Other Linux distributions + may do this differently. </P +><P +> A user can change his private time zone by setting the + TZ environment variable. If it is unset, the system time zone + is assumed. The syntax of the TZ variable is described in the + <TT +CLASS="FUNCTION" +>tzset</TT +> manual page. </P +><P +> The <B +CLASS="COMMAND" +>date</B +> command shows the current date and + time. + + <A +NAME="AEN2466" +HREF="#FTN.AEN2466" +>[1]</A +> + + For example: + +<PRE +CLASS="SCREEN" +><TT +CLASS="PROMPT" +>$</TT +> <TT +CLASS="USERINPUT" +><B +>date</B +></TT +> +<TT +CLASS="COMPUTEROUTPUT" +>Sun Jul 14 21:53:41 EET DST 1996</TT +> +<TT +CLASS="PROMPT" +>$</TT +></PRE +> + + That time is Sunday, 14th of July, 1996, at about ten before + ten at the evening, in the time zone called ``EET DST'' + (which might be East European Daylight Savings Time). + <B +CLASS="COMMAND" +>date</B +> can also show the univeral time: + +<PRE +CLASS="SCREEN" +><TT +CLASS="PROMPT" +>$</TT +> <TT +CLASS="USERINPUT" +><B +>date -u</B +></TT +> +Sun Jul 14 18:53:42 UTC 1996 +<TT +CLASS="COMPUTEROUTPUT" +>Sun Jul 14 18:53:42 UTC 1996</TT +> +<TT +CLASS="PROMPT" +>$</TT +></PRE +> + + <B +CLASS="COMMAND" +>date</B +> is also used to set the kernel's software + clock: + +<PRE +CLASS="SCREEN" +><TT +CLASS="PROMPT" +>#</TT +> <TT +CLASS="USERINPUT" +><B +>date 07142157</B +></TT +> +<TT +CLASS="COMPUTEROUTPUT" +>Sun Jul 14 21:57:00 EET DST 1996</TT +> +<TT +CLASS="PROMPT" +>#</TT +> <TT +CLASS="USERINPUT" +><B +>date</B +></TT +> +<TT +CLASS="COMPUTEROUTPUT" +>Sun Jul 14 21:57:02 EET DST 1996</TT +> +<TT +CLASS="PROMPT" +>#</TT +></PRE +> + + See the <B +CLASS="COMMAND" +>date</B +> manual page for more details; + the syntax is a bit arcane. Only root can set the time. + While each user can have his own time zone, the clock is the + same for everyone. </P +><P +> <B +CLASS="COMMAND" +>date</B +> only shows or sets the software + clock. The <B +CLASS="COMMAND" +>clock</B +> commands syncronizes + the hardware and software clocks. It is used when the system + boots, to read the hardware clock and set the software clock. + If you need to set both clocks, you first set the software clock + with <B +CLASS="COMMAND" +>date</B +>, and then the hardware clock with + <B +CLASS="COMMAND" +>clock -w</B +>. </P +><P +> The <SPAN +CLASS="OPTION" +>-u</SPAN +> option to <B +CLASS="COMMAND" +>clock</B +> + tells it that the hardware clock is in universal time. + You <I +CLASS="EMPHASIS" +>must</I +> use the <SPAN +CLASS="OPTION" +>-u</SPAN +> + option correctly. If you don't, your computer will be quite + confused about what the time is. </P +><P +> The clocks should be changed with care. Many parts of a + Unix system require the clocks to work correctly. For example, + the <B +CLASS="COMMAND" +>cron</B +> daemon runs commands periodically. + If you change the clock, it can be confused of whether + it needs to run the commands or not. On one early Unix + system, someone set the clock twenty years into the future, + and <B +CLASS="COMMAND" +>cron</B +> wanted to run all the periodic + commands for twenty years all at once. Current versions of + <B +CLASS="COMMAND" +>cron</B +> can handle this correctly, but you should + still be careful. Big jumps or backward jumps are more dangeours + than smaller or forward ones. </P +></DIV +><H3 +>Notes</H3 +><TABLE +BORDER="0" +CLASS="FOOTNOTES" +WIDTH="100%" +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="5%" +><A +NAME="FTN.AEN2466" +HREF="x2457.html#AEN2466" +>[1]</A +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="95%" +><P +>Beware of the <B +CLASS="COMMAND" +>time</B +> command, which does + not show the current time.</P +></TD +></TR +></TABLE +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x2451.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="book1.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x2504.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>The hardware and software clocks</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="c2432.html" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>When the clock is wrong</TD +></TR +></TABLE +></DIV +></BODY +></HTML +>
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