130 lines
3.8 KiB
Groff
130 lines
3.8 KiB
Groff
.\" Copyright (C) 1993 by Andrew A. Chernov, Moscow, Russia.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd December 15, 1993
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.Dt ADJKERNTZ 8
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.Os FreeBSD
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.Sh NAME
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.Nm adjkerntz
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.Nd "adjusts the kernel time if the machine runs wall CMOS clock"
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.Sh SYNOPSIS
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.Nm adjkerntz
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.Fl i
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.Nm adjkerntz
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.Fl a
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.Sh DESCRIPTION
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.Nm Adjkerntz
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fixes kernel time (makes it UTC) using the current wall CMOS clock value,
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the current time zone rule and the kernel timezone value. The adjustment is
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enabled only if the file
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.Pa /etc/wall_cmos_clock
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exists, in other cases it is assumed that the machine runs UTC CMOS clock and
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.Nm adjkerntz
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does nothing.
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.Pp
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The adjustment is needed at boot stage and when a time zone
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change occurs, so
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.Nm adjkerntz
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can be called in two forms:
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.Bl -tag -width 4n
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.It Cm Fl i
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initialization call from
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.Pa /etc/rc
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(before any daemons are started).
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.Nm Adjkerntz
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makes the adjustment of kernel clock (CMOS clock not touched)
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and the initial time zone offset is stored into
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.Pa adjkerntz
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kernel variable
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for following subsequent
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.Nm "'adjkerntz -a'"
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calls. Then it goes to background pause which ends with SIGTERM.
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After receiving SIGTERM it acts like
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.Nm "'adjkerntz -a'"
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to be shure to have proper CMOS clock before reboot.
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.It Cm Fl a
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This form is needed, when time zone changes occur.
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.Nm Adjkerntz
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uses the previously stored
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time zone offset and the changed time zone rule to
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produce the new time zone offset, fix the CMOS clock
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(kernel clock not touched)
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and store the new
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offset into
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.Pa adjkerntz
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kernel variable
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too.
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It is recommended to use this form in root's
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.Xr crontab 5
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every half of a hour from 0am to 4am
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since this times matches most modern time zone changes.
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.El
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.Pp
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.Nm Adjkerntz
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clears the kernel timezone structure and makes kernel always run at UTC
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time zone.
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Super-user privilege is required for all operations.
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.Sh ENVIRONMENT
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.Bl -tag -width Fl
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.It Ev TZ
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Time zone change rule, see
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.Xr tzset 3 ;
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not needed when
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.Xr /usr/sbin/tzsetup
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or
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.Xr zic 8
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is used.
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.Sh FILES
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.Bl -tag -width /etc/wall_cmos_clock -compact
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.It Pa /etc/localtime
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Current zoneinfo file, see
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.Xr /usr/sbin/tzsetup
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and
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.Xr zic 8 .
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.It Pa /etc/wall_cmos_clock
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Empty file.
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Presence of it indicates that the machine runs wall CMOS clock,
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absence indicates UTC CMOS clock.
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.Sh SEE ALSO
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.Xr tzset 3 ,
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.Xr zic 8 ,
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.Xr rc 8 ,
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.Xr crontab 5 ,
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.Xr sysctl 8 ,
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.Xr /usr/sbin/tzsetup
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.Sh DIAGNOSTICS
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No diagnostics.
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If any error occurs, an error message printed via
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.Xr syslog 3
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and
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.Nm adjkerntz
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exits with return code greater than zero.
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.Sh AUTHOR
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Andrew A. Chernov <ache@astral.msk.su>
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.Sh HISTORY
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The
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.Nm adjkerntz
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command appeared in FreeBSD 1.0.1
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