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
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.
12 .\" Copyright 2018 Gary Mills
13 .\" Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved.
20 .Nd provide all real-time clock and UTC-lag management
26 The Real Time Clock (RTC) is the hardware device on x86 computers that maintains
28 The RTC is battery-powered, so that it keeps running when the computer is shut
30 It can be set from the BIOS and also from the operating system running on the
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.
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
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 .
52 command is not normally run from a shell prompt; it is generally invoked by the
58 which are used to set the time on a system, invoke
60 to ensure that daylight savings time (DST) is corrected for properly.
64 This option checks for DST and makes corrections to the RTC if necessary.
65 It is normally run once a day by a
69 If there is no RTC time zone or
71 file, this option will do nothing.
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.
78 command is not necessary, and should not be run.
80 This option specifies that the RTC runs in UTC time.
81 As a side effect, it sets the time zone in
84 Windows can operate in UTC time, but requires a registry change to do so.
87 command is not necessary.
89 This option specifies that the RTC tracks local time, including DST changes.
91 It accomodates Windows with no changes.
94 command is necessary to change the RTC when DST is in effect.
96 This option does nothing.
97 It is present for compatibility with Solaris 11.
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
103 with the name of the specified zone and the current UTC lag for that zone.
104 If there is an existing
106 file, this command will update it.
107 If not, this command will create it.
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
115 At boot time, the kernel reads the UTC lag from this file, and uses it to set