Re: [PATCH 1/1] services: ntpd: Make large clock adjustments if necessary.

[Ludovic Courtès]

Leo Famulari <address@hidden> skribis:

> On Thu, Oct 13, 2016 at 07:06:50AM +0200, John Darrington wrote:
>> I think that this should be a configuration item in the service, so that the
>> user can decide whether to have it or not.  I don't think we should force it
>> on the user.   Some applications break if the clock makes large jumps.
>
> I agree. This is really something that the system administrator should
> evaluate and fix on a case-by-case basis.

I agree too!  And I think it’s good idea to have defaults that match
upstream’s defaults.

>> The ntpd authors decided that the default behaviour is not to make large 
>> jumps
>> so I think we should respect that unless there is a good reason to do 
>> otherwise.
>> So I think this should be configurable in /etc/config.scm and the default 
>> should
>> be not to use -g
>
> For me, I have to do this so rarely (and never on the machines I
> currently use) that I am fine with having to run `ntpd -g ...` by hand.
>
> So, if we want to make this configurable in the OS configuration,
> volunteers are welcome to work on it :)

Like this?

diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index 7495179..ce281c5 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -265,11 +265,13 @@ Protocol (DHCP) client, on all the non-loopback network 
interfaces."
   ntp-configuration?
   (ntp      ntp-configuration-ntp
             (default ntp))
-  (servers  ntp-configuration-servers))
+  (servers  ntp-configuration-servers)
+  (allow-large-adjustment? ntp-allow-large-adjustment?
+                           (default #f)))
 
 (define ntp-shepherd-service
   (match-lambda
-    (($ <ntp-configuration> ntp servers)
+    (($ <ntp-configuration> ntp servers allow-large-adjustment?)
      (let ()
        ;; TODO: Add authentication support.
        (define config
@@ -296,7 +298,10 @@ restrict -6 ::1\n"))
               (requirement '(user-processes networking))
               (start #~(make-forkexec-constructor
                         (list (string-append #$ntp "/bin/ntpd") "-n"
-                              "-c" #$ntpd.conf "-u" "ntpd")))
+                              "-c" #$ntpd.conf "-u" "ntpd"
+                              #$@(if allow-large-adjustment?
+                                     '("-g")
+                                     '()))))
               (stop #~(make-kill-destructor))))))))
 
 (define %ntp-accounts
@@ -331,10 +336,13 @@ restrict -6 ::1\n"))
                                           ntp-service-activation)))))
 
 (define* (ntp-service #:key (ntp ntp)
-                      (servers %ntp-servers))
+                      (servers %ntp-servers)
+                      allow-large-adjustment?)
   "Return a service that runs the daemon from @var{ntp}, the
 @uref{http://www.ntp.org, Network Time Protocol package}.  The daemon will
-keep the system clock synchronized with that of @var{servers}."
+keep the system clock synchronized with that of @var{servers}.
address@hidden determines whether @command{ntpd} is allowed to
+make an initial adjustment of more than 1,000 seconds."
   (service ntp-service-type
            (ntp-configuration (ntp ntp) (servers servers))))
 

If that’s fine with you, I’ll commit it with a doc update.

Thanks,
Ludo’.