'\" te
.\" Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved.
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.TH rtc 1M "3 Oct 2003" "SunOS 5.11" "System Administration Commands"
.SH NAME
rtc \- provide all real-time clock and GMT-lag management
.SH SYNOPSIS
.LP
.nf
\fB/usr/sbin/rtc\fR [\fB-c\fR] [\fB-z\fR \fIzone-name\fR]
.fi

.SH DESCRIPTION
.sp
.LP
On x86 systems, the \fBrtc\fR command reconciles the difference in the way that
time is established between UNIX and MS-DOS systems. UNIX systems utilize
Greenwich Mean Time (\fBGMT\fR), while \fBMS-DOS\fR systems utilize local time.
.sp
.LP
Without arguments, \fBrtc\fR displays the currently configured time zone
string. The currently configured time zone string is based on what was last
recorded by \fBrtc\fR\fB-z\fR \fIzone-name\fR.
.sp
.LP
The \fBrtc\fR command is not normally run from a shell prompt; it is generally
invoked by the system. Commands such as \fBdate\fR(1) and \fBrdate\fR(1M),
which are used to set the time on a system, invoke \fB/usr/sbin/rtc\fR \fB-c\fR
to ensure that daylight savings time (\fBDST\fR) is corrected for properly.
.SH OPTIONS
.sp
.ne 2
.mk
.na
\fB\fB-c\fR\fR
.ad
.RS 16n
.rt  
This option checks for \fBDST\fR and makes corrections if necessary. It is
normally run once a day by a \fBcron\fR job.
.sp
If there is no \fBRTC\fR time zone or \fB/etc/rtc_config\fR file, this option
will do nothing.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\fR\fB-z\fR\fB \fR\fIzone-name\fR\fR
.ad
.RS 16n
.rt  
This option, which is normally run by the system at software installation time,
is used to specify the time zone in which the \fBRTC\fR is to be maintained. It
updates the configuration file \fB/etc/rtc_config\fR with the name of the
specified zone and the current \fBGMT\fR lag for that zone. If there is an
existing \fBrtc_config\fR file, this command will update it. If not, this
command will create it.
.RE

.SH FILES
.sp
.ne 2
.mk
.na
\fB\fB/etc/rtc_config\fR\fR
.ad
.RS 19n
.rt  
The data file used to record the time zone and \fBGMT\fR lag. This file is
completely managed by \fB/usr/sbin/rtc\fR, and it is read by the kernel.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Architecturex86
.TE

.SH SEE ALSO
.sp
.LP
\fBdate\fR(1), \fBrdate\fR(1M), \fBattributes\fR(5)