1 '\" te
2 .\" Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved.
3 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
4 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
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6 .TH RTC 1M "Oct 3, 2003"
7 .SH NAME
8 rtc \- provide all real-time clock and GMT-lag management
9 .SH SYNOPSIS
10 .LP
11 .nf
12 \fB/usr/sbin/rtc\fR [\fB-c\fR] [\fB-z\fR \fIzone-name\fR]
13 .fi
14
15 .SH DESCRIPTION
16 .sp
17 .LP
18 On x86 systems, the \fBrtc\fR command reconciles the difference in the way that
19 time is established between UNIX and MS-DOS systems. UNIX systems utilize
20 Greenwich Mean Time (\fBGMT\fR), while \fBMS-DOS\fR systems utilize local time.
21 .sp
22 .LP
23 Without arguments, \fBrtc\fR displays the currently configured time zone
24 string. The currently configured time zone string is based on what was last
25 recorded by \fBrtc\fR\fB-z\fR \fIzone-name\fR.
26 .sp
27 .LP
28 The \fBrtc\fR command is not normally run from a shell prompt; it is generally
29 invoked by the system. Commands such as \fBdate\fR(1) and \fBrdate\fR(1M),
30 which are used to set the time on a system, invoke \fB/usr/sbin/rtc\fR \fB-c\fR
31 to ensure that daylight savings time (\fBDST\fR) is corrected for properly.
32 .SH OPTIONS
33 .sp
34 .ne 2
35 .na
36 \fB\fB-c\fR\fR
37 .ad
38 .RS 16n
39 This option checks for \fBDST\fR and makes corrections if necessary. It is
40 normally run once a day by a \fBcron\fR job.
41 .sp
42 If there is no \fBRTC\fR time zone or \fB/etc/rtc_config\fR file, this option
43 will do nothing.
44 .RE
45
46 .sp
47 .ne 2
48 .na
49 \fB\fB\fR\fB-z\fR\fB \fR\fIzone-name\fR\fR
50 .ad
51 .RS 16n
52 This option, which is normally run by the system at software installation time,
53 is used to specify the time zone in which the \fBRTC\fR is to be maintained. It
54 updates the configuration file \fB/etc/rtc_config\fR with the name of the
55 specified zone and the current \fBGMT\fR lag for that zone. If there is an
56 existing \fBrtc_config\fR file, this command will update it. If not, this
57 command will create it.
58 .RE
59
60 .SH FILES
61 .sp
62 .ne 2
63 .na
64 \fB\fB/etc/rtc_config\fR\fR
65 .ad
66 .RS 19n
67 The data file used to record the time zone and \fBGMT\fR lag. This file is
68 completely managed by \fB/usr/sbin/rtc\fR, and it is read by the kernel.
69 .RE
70
71 .SH ATTRIBUTES
72 .sp
73 .LP
74 See \fBattributes\fR(5) for descriptions of the following attributes:
75 .sp
76
77 .sp
78 .TS
79 box;
80 c | c
81 l | l .
82 ATTRIBUTE TYPE ATTRIBUTE VALUE
83 _
84 Architecture x86
85 .TE
86
87 .SH SEE ALSO
88 .sp
89 .LP
90 \fBdate\fR(1), \fBrdate\fR(1M), \fBattributes\fR(5)
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1 .\"
2 .\" This file and its contents are supplied under the terms of the
3 .\" Common Development and Distribution License ("CDDL"), version 1.0.
4 .\" You may only use this file in accordance with the terms of version
5 .\" 1.0 of the CDDL.
6 .\"
7 .\" A full copy of the text of the CDDL should have accompanied this
8 .\" source. A copy of the CDDL is also available via the Internet at
9 .\" http://www.illumos.org/license/CDDL.
10 .\"
11 .\"
12 .\" Copyright 2018 Gary Mills
13 .\" Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved.
14 .\"
15 .Dd January 31, 2018
16 .Dt RTC 1M
17 .Os
18 .Sh NAME
19 .Nm rtc
20 .Nd provide all real-time clock and UTC-lag management
21 .Sh SYNOPSIS
22 .Nm
23 .Op Fl csuvw
24 .Op Fl z Ar zone-name
25 .Sh DESCRIPTION
26 The Real Time Clock (RTC) is the hardware device on x86 computers that maintains
27 the date and time.
28 The RTC is battery-powered, so that it keeps running when the computer is shut
29 down.
30 It can be set from the BIOS and also from the operating system running on the
31 computer.
32 The RTC has no setting for the time zone or for Daylight Saving Time (DST).
33 It relies on the operating system for these facilities and for automatic changes
34 between standard time and DST.
35 .Pp
36 On x86 systems, the
37 .Nm
38 command reconciles the difference in the way that time is established between
39 UNIX and Windows systems.
40 The internal clock on UNIX systems utilizes Universal Coordinated Time (UTC)
41 while Windows systems usually expect the RTC to run in local time, including DST
42 changes.
43 .Pp
44 Without arguments,
45 .Nm
46 displays the currently configured time zone string for the RTC.
47 The currently configured time zone string is based on what was last recorded by
48 .Nm Fl z Ar zone-name .
49 .Pp
50 The
51 .Nm
52 command is not normally run from a shell prompt; it is generally invoked by the
53 system.
54 Commands such as
55 .Xr date 1
56 and
57 .Xr rdate 1M ,
58 which are used to set the time on a system, invoke
59 .Nm Fl c
60 to ensure that daylight savings time (DST) is corrected for properly.
61 .Sh OPTIONS
62 .Bl -tag -width Ds
63 .It Fl c
64 This option checks for DST and makes corrections to the RTC if necessary.
65 It is normally run once a day by a
66 .Xr cron 1M
67 job.
68 .Pp
69 If there is no RTC time zone or
70 .Pa /etc/rtc_config
71 file, this option will do nothing.
72 .It Fl s
73 This option specifies that the RTC runs in local standard time all year round.
74 It is incompatible with Windows, but is convenient if only one operating system
75 is to be run on the computer.
76 The
77 .Xr cron 1M
78 command is not necessary, and should not be run.
79 .It Fl u
80 This option specifies that the RTC runs in UTC time.
81 As a side effect, it sets the time zone in
82 .Pa /etc/rtc_config
83 to UTC.
84 Windows can operate in UTC time, but requires a registry change to do so.
85 The
86 .Xr cron 1M
87 command is not necessary.
88 .It Fl v
89 This option specifies that the RTC tracks local time, including DST changes.
90 This is the default.
91 It accomodates Windows with no changes.
92 The
93 .Xr cron 1M
94 command is necessary to change the RTC when DST is in effect.
95 .It Fl w
96 This option does nothing.
97 It is present for compatibility with Solaris 11.
98 .It Fl z Ar zone-name
99 This option, which is normally run by the system at software installation time,
100 is used to specify the time zone in which the RTC is to be maintained.
101 It updates the configuration file
102 .Pa /etc/rtc_config
103 with the name of the specified zone and the current UTC lag for that zone.
104 If there is an existing
105 .Pa /etc/rtc_config
106 file, this command will update it.
107 If not, this command will create it.
108 .El
109 .Sh FILES
110 .Bl -tag -width "/etc/rtc_config"
111 .It Pa /etc/rtc_config
112 The data file used to record the time zone and UTC lag.
113 This file is completely managed by
114 .Nm .
115 At boot time, the kernel reads the UTC lag from this file, and uses it to set
116 the system time.
117 .El
118 .Sh ARCHITECTURE
119 .Sy x86
120 .Sh SEE ALSO
121 .Xr date 1 ,
122 .Xr cron 1M ,
123 .Xr rdate 1M ,
124 .Xr attributes 5
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