rtc(1M) System Administration Commands rtc(1M)NAME
rtc - provide all real-time clock and GMT-lag management
SYNOPSIS
/usr/sbin/rtc [-c] [-z zone-name]
DESCRIPTION
On x86 systems, the rtc command reconciles the difference in the way that time is established between UNIX and MS-DOS systems. UNIX systems
utilize Greenwich Mean Time (GMT), while MS-DOS systems utilize local time.
Without arguments, rtc displays the currently configured time zone string. The currently configured time zone string is based on what was
last recorded by rtc-z zone-name.
The rtc command is not normally run from a shell prompt; it is generally invoked by the system. Commands such as date(1) and rdate(1M),
which are used to set the time on a system, invoke /usr/sbin/rtc -c to ensure that daylight savings time (DST) is corrected for properly.
OPTIONS -c This option checks for DST and makes corrections if necessary. It is normally run once a day by a cron job.
If there is no RTC time zone or /etc/rtc_config file, this option will do nothing.
-z 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 /etc/rtc_config with the name of the specified zone and the
current GMT lag for that zone. If there is an existing rtc_config file, this command will update it. If not, this command
will create it.
FILES
/etc/rtc_config The data file used to record the time zone and GMT lag. This file is completely managed by /usr/sbin/rtc, and it is read
by the kernel.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Architecture |x86 |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO date(1), rdate(1M), attributes(5)SunOS 5.11 3 Oct 2003 rtc(1M)
Check Out this Related Man Page
TIMEDATECTL(1) timedatectl TIMEDATECTL(1)NAME
timedatectl - Control the system time and date
SYNOPSIS
timedatectl [OPTIONS...] {COMMAND}
DESCRIPTION
timedatectl may be used to query and change the system clock and its settings.
OPTIONS
The following options are understood:
-h, --help
Prints a short help text and exits.
--version
Prints a short version string and exits.
--no-pager
Do not pipe output into a pager.
--no-ask-password
Do not query the user for authentication for privileged operations.
-P, --privileged
Acquire privileges via PolicyKit before executing the operation.
-H, --host
Execute the operation remotely. Specify a hostname, or username and hostname separated by "@", to connect to. This will use SSH to talk
to a remote system.
--adjust-system-clock
If set-local-rtc is invoked and this option is passed, the system clock is synchronized from the RTC again, taking the new setting into
account. Otherwise, the RTC is synchronized from the system clock.
The following commands are understood:
status
Show current settings of the system clock and RTC.
set-time [TIME]
Set the system clock to the specified time. This will also update the RTC time accordingly. The time may be specified in the format
"2012-10-30 18:17:16".
set-timezone [TIMEZONE]
Set the system time zone to the specified value. Available timezones can be listed with list-timezones. If the RTC is configured to be
in the local time, this will also update the RTC time. This call will alter the /etc/localtime symlink. See localtime(5) for more
information.
list-timezones
List available time zones, one per line. Entries from the list can be set as the system timezone with set-timezone.
set-local-rtc [BOOL]
Takes a boolean argument. If "0", the system is configured to maintain the RTC in universal time. If "1", it will maintain the RTC in
local time instead. Note that maintaining the RTC in the local timezone is not fully supported and will create various problems with
time zone changes and daylight saving adjustments. If at all possible, keep the RTC in UTC mode. Note that invoking this will also
synchronize the RTC from the system clock, unless --adjust-system-clock is passed (see above). This command will change the 3rd line of
/etc/adjtime, as documented in hwclock(8).
set-ntp [BOOL]
Takes a boolean argument. Controls whether NTP based network time synchronization is enabled (if available).
EXIT STATUS
On success, 0 is returned, a non-zero failure code otherwise.
ENVIRONMENT
$SYSTEMD_PAGER
Pager to use when --no-pager is not given; overrides $PAGER. Setting this to an empty string or the value "cat" is equivalent to
passing --no-pager.
EXAMPLES
Show current settings:
$ timedatectl
Local time: Fri, 2012-11-02 09:26:46 CET
Universal time: Fri, 2012-11-02 08:26:46 UTC
RTC time: Fri, 2012-11-02 08:26:45
Timezone: Europe/Warsaw
UTC offset: +0100
NTP enabled: no
NTP synchronized: no
RTC in local TZ: no
DST active: no
Last DST change: CEST -> CET, DST became inactive
Sun, 2012-10-28 02:59:59 CEST
Sun, 2012-10-28 02:00:00 CET
Next DST change: CET -> CEST, DST will become active
the clock will jump one hour forward
Sun, 2013-03-31 01:59:59 CET
Sun, 2013-03-31 03:00:00 CEST
Enable an NTP daemon (chronyd):
$ timedatectl set-ntp true
==== AUTHENTICATING FOR org.freedesktop.timedate1.set-ntp ===
Authentication is required to control whether network time synchronization shall be enabled.
Authenticating as: user
Password: ********
==== AUTHENTICATION COMPLETE ===
$ systemctl status chronyd.service
chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled)
Active: active (running) since Fri, 2012-11-02 09:36:25 CET; 5s ago
...
SEE ALSO systemd(1), hwclock(8), date(1), localtime(5), systemctl(1), systemd-timedated.service(8)systemd 208TIMEDATECTL(1)