Date: Mon, 19 Apr 2010 09:49:24 +0300 From: Daniel Braniss <danny@cs.huji.ac.il> To: Andrew Reilly <areilly@bigpond.net.au> Cc: freebsd-stable@freebsd.org, Jeremy Chadwick <freebsd@jdc.parodius.com> Subject: Re: rc(8) script -- waiting for the network to become usable Message-ID: <E1O3knM-000MaT-3E@kabab.cs.huji.ac.il> In-Reply-To: <20100418232420.GA4620@duncan.reilly.home> References: <20100418213727.GA98129@icarus.home.lan> <20100418232420.GA4620@duncan.reilly.home>
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> On Sun, Apr 18, 2010 at 02:37:27PM -0700, Jeremy Chadwick wrote: > > I'd like to discuss the possibility of introduction of a new script into > > /etc/rc.d base system a script, which when enabled, would provide a way > > to wait until the IP networking layer (using ping(8)) is up and usable > > before continuing with daemon startup. > > > > Let's discuss. :-) > > > > > > HISTORY > > ========= > > The situation which brought this debacle to my attention: > > > > I found that on reboot of some of our systems, ntpdate (used to sync the > > clock initially before ntpd would be started) wouldn't work. The daemon > > would report that it couldn't resolve any of the FQDNs within ntp.conf, > > and would therefore act as a no-op before continuing on. > > By way of discussion, I'd just like to re-iterate what I > said the first time around: it must be understood that this > sort of thing is a (necessary) hacky-workaround that should > ultimately be unnecessary. In preference, we should work on > the failing daemons or hassle up-stream daemon authors so > that the daemons in question either (a) retry until they *do* > get the information they're after or (b) fail properly, so > that they can be restarted by an external process monitoring > framework like sysutils/daemontools or launchd. The reasoning > is simple: network outage is something that can happen even > after startup, and when network connectivity returns, the > routing and addresses that are visible won't necessarily be the > same. Consider laptops that suspend, as a particular example. > Or mobile devices that switch from wi-fi to cellular networking > to no connectivity on a regular basis. The "get it right at > boot time" model is important and traditional, but (I think) > a fragile and diminishing fraction of use cases. Our rc-ng > framework favours solution (a). I'm more a fan of approach (b), > myself: I use daemontools for many services, and I like the way > that launchd works on my Mac laptops. I think that rc is being overloaded yet again(*), and a launchDaemon kind of solution should be followed, maybe even as a replacement for inetd? /blah (*): in the begining rc would do everything, but life was simple - no internet, then it got complicated, too many daemons, so inetd was invented, things were back in control, for a while. Then sysv invented init.d/init levels, then rc-ng came along, though it solves many problems, 1) the order of things, 2) easy to configure services, it's getting complicated to get 1 'correctly'. blah/ danny
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