I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-between-ntpd...
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
thanks
Date: Sunday, February 05, 2017 10:26:05 -0500 From: Robert Moskowitz rgm@htt-consult.com
I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-bet ween-ntpd-and-chronyd/
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
Where I have somewhat similar issues, I have historically used a crontab "@reboot" entry to call ntpdate which gets the clock set correctly. From there ntp keeps it in sync.
This can now be accomplished with ntpd, and ntpdate is threatened with depreciation/retirement. See the top of the ntpdate man page for more details.
On 05/02/17 16:15, Richard wrote:
Date: Sunday, February 05, 2017 10:26:05 -0500 From: Robert Moskowitz rgm@htt-consult.com
I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-bet ween-ntpd-and-chronyd/
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
Where I have somewhat similar issues, I have historically used a crontab "@reboot" entry to call ntpdate which gets the clock set correctly. From there ntp keeps it in sync.
This can now be accomplished with ntpd, and ntpdate is threatened with depreciation/retirement. See the top of the ntpdate man page for more details.
The NTP configuration option you may be after is "tinker panic 0" which allows NTP to make big jumps as often as required. See ntp_misc(5). There is a related discussion with making VMs take big jumps at https://www.centos.org/forums/viewtopic.php?f=16&t=61186&p=258254#p2...
On 02/05/2017 11:58 AM, J Martin Rushton wrote:
On 05/02/17 16:15, Richard wrote:
Date: Sunday, February 05, 2017 10:26:05 -0500 From: Robert Moskowitz rgm@htt-consult.com
I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-bet ween-ntpd-and-chronyd/
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
Where I have somewhat similar issues, I have historically used a crontab "@reboot" entry to call ntpdate which gets the clock set correctly. From there ntp keeps it in sync.
This can now be accomplished with ntpd, and ntpdate is threatened with depreciation/retirement. See the top of the ntpdate man page for more details.
The NTP configuration option you may be after is "tinker panic 0" which allows NTP to make big jumps as often as required. See ntp_misc(5). There is a related discussion with making VMs take big jumps at https://www.centos.org/forums/viewtopic.php?f=16&t=61186&p=258254#p2...
Thanks. I will look at this. All I was seeing was to use burst and iburst, but they would not make the really big jump needed after boot.
On Sun, 2017-02-05 at 12:30 -0500, Robert Moskowitz wrote:
On 02/05/2017 11:58 AM, J Martin Rushton wrote:
On 05/02/17 16:15, Richard wrote:
Date: Sunday, February 05, 2017 10:26:05 -0500 From: Robert Moskowitz rgm@htt-consult.com
I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences -bet ween-ntpd-and-chronyd/
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
Where I have somewhat similar issues, I have historically used a crontab "@reboot" entry to call ntpdate which gets the clock set correctly. From there ntp keeps it in sync.
This can now be accomplished with ntpd, and ntpdate is threatened with depreciation/retirement. See the top of the ntpdate man page for more details.
The NTP configuration option you may be after is "tinker panic 0" which allows NTP to make big jumps as often as required. See ntp_misc(5). There is a related discussion with making VMs take big jumps at https://www.centos.org/forums/viewtopic.php?f=16&t=61186&p=258254#p 258254
Thanks. I will look at this. All I was seeing was to use burst and iburst, but they would not make the really big jump needed after boot.
With NTP you could use the ntpdate.service as well as/ before ntpd.service. the former is supposed to set the clock once BEFORE ntpd is started. See: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_L inux/6/html/Deployment_Guide/s1-Configure_ntpdate_Servers.html Ntpdate seems to work on RHEL/Centos 7 as well...
/Louis
On 02/05/2017 11:58 AM, J Martin Rushton wrote:
On 05/02/17 16:15, Richard wrote:
Date: Sunday, February 05, 2017 10:26:05 -0500 From: Robert Moskowitz rgm@htt-consult.com
I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-bet ween-ntpd-and-chronyd/
My server is up all the time and will serve time to internal systems (via DHCP options).
Caveat is that my server is an armv7 (Cubieboard2) which does not have an RTC (no battery). So whenever the system boots, the time is ZERO (Dec 31, 1969 or some such).
Chrony fixes this really fast; shortly after boot the time is good. Chrony CAN be configed as an internal time server. But chrony does not seem to step the clock for any adjustments needed. It is more important that this systems time be right all the time than to avoid clock steps.
This brings me back to NTP, which normally takes hours to bring the time from ZERO to current, but keeps the time correct.
So:
Can Chrony check the time, say once a day?
Or can NTP make a BIG time jump all at once (on system restart)?
Where I have somewhat similar issues, I have historically used a crontab "@reboot" entry to call ntpdate which gets the clock set correctly. From there ntp keeps it in sync.
This can now be accomplished with ntpd, and ntpdate is threatened with depreciation/retirement. See the top of the ntpdate man page for more details.
The NTP configuration option you may be after is "tinker panic 0" which allows NTP to make big jumps as often as required. See ntp_misc(5). There is a related discussion with making VMs take big jumps at https://www.centos.org/forums/viewtopic.php?f=16&t=61186&p=258254#p2...
So, if I understand the man page, this command should be the first one in /etc/ntp.conf
-
J Martin Rushton -
Louis Lagendijk -
Richard -
Robert Moskowitz