[pkg-ntp-maintainers] Bug#731594: Bug#731594: debian-installer: time synchronisation should be installed by default

[Bdale Garbee]

Dmitrijs Ledkovs <xnox at debian.org> writes:

> Servers that rarely (re)configure network or boot, can also setup cron
> to call to ntpdate or install an NTP client daemon when they are first
> configured.

FWIW, calling ntpdate from cron is a *horrible* idea.

Since I agree that having time sync be a default part of a Debian
installation would be a good idea, let me put a few thoughts down here
and articulate what I think we should do.

On a system like a server with at least one fixed-configuration network
interface, unless the hardware clock has completely failed, the initial
system time won't be grossly off, and just installing an ntp daemon is a
better plan.  Even if the hardware clock *has* failed, Debian's ntp
packaging uses the -g option to the daemon by default, so that once the
daemon has talked to enough peers/servers to know what time it is, it
will always slew the clock one time no matter how far off it is at
daemon launch. 

On a client system like a notebook that only has dynamic network
connectivity, and may not be on the net at all at boot, the best
strategy seem to be to rely on the hardware clock at boot and only worry
about network time sync when there's networking available.  For the past
couple years, I've been using the openntpd package on my notebook, which
has an if-up.d script that does a force-reload on each network interface
up event, and in practice I've been quite happy with the results.

I looked at chrony briefly several years ago and wasn't impressed, but
I'm peripherally aware that it has been worked on quite a bit since then
and probably deserves another look.  It claims to have been specifically
written to handle well the case of a system that's not always on the net.

Looking at the size of the packages, ntp is largest due to the inclusion
of drivers for various reference clocks, etc.  Chrony is also a very
large package, ntpdate is much larger than you'd expect, and openntpd is
quite small by comparison to either ntp or chrony.  Here are the Size:
and Installed-Size: values for each based on the current sid packages:

      ntp      559578  1226
      chrony   395400   743
      ntpdate   81930   227
      openntpd  64068   103

I care a lot about the size of our base install, and openntpd seems to
do everything I need just fine as far as I can tell.  So, without going
off to study chrony which I really don't know at all, if I were making
this decision, I'd be inclined to make openntpd standard, avoid ntpdate
entirely, and assume users who really want to run stratum-1 NTP servers
know how to install and optimally configure ntp.

Bdale
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