How disable system time update?

[Killertechno]

Hi to all, I'm making tests using DS3231 RTC and GPS receiver.
At boot I write into DS3231 date from GPS receiver (starting at 1 Jan 2000), but when accessing to Raspberry through ssh I can see system time and RTC time are updated to 2019.
Disabling internet access on router I can correctly find RTC date at 1 Jan 2000.

I removed hwclock and ntp (sudo apt-get remove ntp, sudo apt-get remove fake-hwclock) and renamed ntp.conf to _ntp.conf.

I still find updated time when internet connection available.

[email protected]:~ $ uname -a
Linux raspberrypi 4.14.34+ #1110 Mon Apr 16 14:51:42 BST 2018 armv6l GNU/Linux
[email protected]:~ $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 9.4 (stretch)
Release: 9.4
Codename: stretch
[email protected]:~ $

How can I do to disable updating system time?
Thanks.

[DirkS]

Stretch does not use ntp. Sync is organised by the systemd-timesyncd service.
To disable it use

Code: Select all

sudo systemctl stop systemd-timesyncd
sudo systemctl disable systemd-timesyncd

[Andyroo]

Unless my math is out (and it could be) that chip could loose 3 minutes a year depending on temp.

I would be interested to know how you get on with it

[Killertechno]

Unless my math is out (and it could be) that chip could loose 3 minutes a year depending on temp.

I would be interested to know how you get on with it

Yes, maximum drift would be 63 seconds (within 0 to 40 °C), or 110 seconds (-40 to 85 °C) after 1 year (365 days).
I check sync alignment with GPS every 3 hours.

[Killertechno]

sudo systemctl stop systemd-timesyncd
sudo systemctl disable systemd-timesyncd

Still getting time updated when internet available....

[epoch1970]

I would try the "timedatectl" command
I believe there is a chance systemd-timesyncd might be revived in some cases, e.g. ntp server info provided via DHCP.
https://wiki.archlinux.org/index.php/systemd-timesyncd