1

My system:
Linux Mint 17.2 MATE 32-bit

My settings:
Menu -> Administration -> Time and Date -> Configuration = Manual (that means do not connect to internet time servers)
I do NOT have ntp installed.

But nevertheless, on every boot my computer's clock is being synchronized with true time.
What should I do to disable it?

2
  • In my view, your question lacks a description of how you modify the system time in this scenario, and what you mean by "true time". It may be the case that you only change the operating system's time without also changing the real-time clock, and that your system sets the system time from the real-time clock during boot. But it's impossible to tell because you don't provide the beforementioned information.
    – Run CMD
    Oct 5, 2015 at 8:26
  • @ClassStacker - My test method: 1) set system time = "true" time + 15 minutes, 2) restart computer, enter BIOS Setup and see that BIOS RTC time is still 15 minutes ahead, 3) boot into Linux and see than time is again "true" Oct 5, 2015 at 8:45

2 Answers 2

1

Given your comment, it can be excluded that your OS re-synchronises with the HW RTC.

I believe that the Mint administration only supports ntpd from the ntp package. But there are other ways to sync your system with network time (and in fact, ntpd is not necessarily the best choice).

You could have chrony or ntpdate installed. They may sync your OS time regardless of the Mint system settings.

Edit

If you want to keep ntpdate, that's also possible. Quoting /usr/share/doc/ntpdate/README.Debian (Linux Mint is derived from Debian):

ntpdate is run whenever a network interface is brought up. To adjust this behavior, the file /etc/network/if-up.d/ntpdate should be edited.

It is easy to adjust /etc/network/if-up.d/ntpdate for your needs. It tests for a variety of conditions before it runs ntpdate (or rather ntpdate-debian. You can even e.g. have it check for the presence of a file somewhere in your home directory to stop the script.

Add something along these lines after the other tests but before the opening round bracket which starts the lock file handling:

if [ -e ~myaccount/settings/dontrun-ntpdate-automatically.txt ]; then
  exit 0
fi
7
  • Yes, I have ntpdate on my system. But how can I find the place where ntpdate is invoked at boot time? Oct 5, 2015 at 9:31
  • @EgorSkriptunoff I'm not sure where Mint does this, but the Mint page for ntpdate seems to suggest that it's part of the setup. I would suspect that it is run when a network connection becomes available; running it at boot-time without connectivity would be a poor approach. Why don't you delete the package and use rdate instead, which is intended for manual use only?
    – Run CMD
    Oct 5, 2015 at 10:00
  • Is it a good idea to remove some application while it is still in use in some root scripts? Oct 5, 2015 at 10:12
  • My suggestion is to remove the package, not the application. The package management of Mint (based on Debian or Ubuntu, which itself is based on Debian) is supposed to remove any dependencies. If my assumtion is correct and a call to ntpdate is executed when the network becomes available, this call will be removed when you uninstall the package. If nothing was configured manually, that is.
    – Run CMD
    Oct 5, 2015 at 10:18
  • @EgorSkriptunoff So, did you try it, does it work?
    – Run CMD
    Oct 6, 2015 at 6:35
2

As can be seen in the syslog, a connection to ntp.ubuntu.com is made on each connection to a (WiFi) network. To block it, add following to /etc/hosts:

# block clock synchronization by ntpdate
127.0.0.1 ntp.ubuntu.com

The advantage of this over adding exit 0 to /etc/network/if-up.d/ntpdate as suggested in https://superuser.com/a/982325 is that it won't be reverted on next update of the ntpdate package, which that file is part of - see http://packages.ubuntu.com/trusty/i386/ntpdate/filelist.

2
  • 1
    On the other hand, this will prevent the user from running ntpdate manually as well. Not sure about Ubuntu, but Debian doesn't overwrite modified files on package upgrade without asking you first. Oct 31, 2015 at 21:26
  • @DmitryGrigoryev it does not prevent the user from running ntupdate any more than the other approach, i.e. the user can edit /etc/hosts and comment the line, or the user can remove (and later recreate if needed) the file "dontrun-ntpdate-automatically.txt" mentioned in the other solution. Which you choose is more a matter or taste, or how you want to document. If we go further, this approach only stops ALL calls to ntp.ubuntu.com, however if the config was to change or other packages might reach other ntp servers and still cause an update. But then again, similar issues with the other solution
    – LMSingh
    Jan 30 at 21:32

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