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Diffstat (limited to 'usr/src/man/man8/rtc.8')
| -rw-r--r-- | usr/src/man/man8/rtc.8 | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/usr/src/man/man8/rtc.8 b/usr/src/man/man8/rtc.8 new file mode 100644 index 0000000000..01151e3d6b --- /dev/null +++ b/usr/src/man/man8/rtc.8 @@ -0,0 +1,124 @@ +.\" +.\" This file and its contents are supplied under the terms of the +.\" Common Development and Distribution License ("CDDL"), version 1.0. +.\" You may only use this file in accordance with the terms of version +.\" 1.0 of the CDDL. +.\" +.\" A full copy of the text of the CDDL should have accompanied this +.\" source. A copy of the CDDL is also available via the Internet at +.\" http://www.illumos.org/license/CDDL. +.\" +.\" +.\" Copyright 2018 Gary Mills +.\" Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved. +.\" +.Dd January 31, 2018 +.Dt RTC 8 +.Os +.Sh NAME +.Nm rtc +.Nd provide all real-time clock and UTC-lag management +.Sh SYNOPSIS +.Nm +.Op Fl csuvw +.Op Fl z Ar zone-name +.Sh DESCRIPTION +The Real Time Clock (RTC) is the hardware device on x86 computers that maintains +the date and time. +The RTC is battery-powered, so that it keeps running when the computer is shut +down. +It can be set from the BIOS and also from the operating system running on the +computer. +The RTC has no setting for the time zone or for Daylight Saving Time (DST). +It relies on the operating system for these facilities and for automatic changes +between standard time and DST. +.Pp +On x86 systems, the +.Nm +command reconciles the difference in the way that time is established between +UNIX and Windows systems. +The internal clock on UNIX systems utilizes Universal Coordinated Time (UTC) +while Windows systems usually expect the RTC to run in local time, including DST +changes. +.Pp +Without arguments, +.Nm +displays the currently configured time zone string for the RTC. +The currently configured time zone string is based on what was last recorded by +.Nm Fl z Ar zone-name . +.Pp +The +.Nm +command is not normally run from a shell prompt; it is generally invoked by the +system. +Commands such as +.Xr date 1 +and +.Xr rdate 8 , +which are used to set the time on a system, invoke +.Nm Fl c +to ensure that daylight savings time (DST) is corrected for properly. +.Sh OPTIONS +.Bl -tag -width Ds +.It Fl c +This option checks for DST and makes corrections to the RTC if necessary. +It is normally run once a day by a +.Xr cron 8 +job. +.Pp +If there is no RTC time zone or +.Pa /etc/rtc_config +file, this option will do nothing. +.It Fl s +This option specifies that the RTC runs in local standard time all year round. +It is incompatible with Windows, but is convenient if only one operating system +is to be run on the computer. +The +.Xr cron 8 +command is not necessary, and should not be run. +.It Fl u +This option specifies that the RTC runs in UTC time. +As a side effect, it sets the time zone in +.Pa /etc/rtc_config +to UTC. +Windows can operate in UTC time, but requires a registry change to do so. +The +.Xr cron 8 +command is not necessary. +.It Fl v +This option specifies that the RTC tracks local time, including DST changes. +This is the default. +It accomodates Windows with no changes. +The +.Xr cron 8 +command is necessary to change the RTC when DST is in effect. +.It Fl w +This option does nothing. +It is present for compatibility with Solaris 11. +.It Fl z Ar zone-name +This option, which is normally run by the system at software installation time, +is used to specify the time zone in which the RTC is to be maintained. +It updates the configuration file +.Pa /etc/rtc_config +with the name of the specified zone and the current UTC lag for that zone. +If there is an existing +.Pa /etc/rtc_config +file, this command will update it. +If not, this command will create it. +.El +.Sh FILES +.Bl -tag -width "/etc/rtc_config" +.It Pa /etc/rtc_config +The data file used to record the time zone and UTC lag. +This file is completely managed by +.Nm . +At boot time, the kernel reads the UTC lag from this file, and uses it to set +the system time. +.El +.Sh ARCHITECTURE +.Sy x86 +.Sh SEE ALSO +.Xr date 1 , +.Xr attributes 7 , +.Xr cron 8 , +.Xr rdate 8 |