LinuxSA Mailing list archives

  From: Daryl Tester <Daryl.Tester@iocane.com.au>
  To  : Alan Kennington <akenning@topology.org>
  Date: Sun, 22 Jul 2001 12:31:26 +0930

Re: BIND 9.1.0 fails badly

Alan Kennington wrote:

> That sounds good. The documentation indicates that it is indeed
> a simple script for chekcing status and sending e-mail notifications.

Won't this fail to send email if your DNS resolver/server is down?
(oh dang, there goes me bringing down everyone's solutions again -
I'd better off something of my own).

A solution that springs to mind (given that my mind still isn't
awake this time of Sunday afternoon) would be to set up a respawn
entry in inittab, and set bind to spawn in non daemon mode so
that it doesn't background itself and cause multiple binds to
start (and fail).  Doesn't help if something environmentally
is continually killing BIND, though (eg, bad config).

> It's a little disappointing, though, to have to continually
> be setting up watchdog things to get software to work correctly.

It's software - can you guarantee that any piece of software
that you've written is 100% reliable, given that things like
C libraries (presuming you wrote it in C) are outside of your
control AND have been known to cause problems?  I certainly
can't, and I'm a particularly anal programmer (picture buttocks
with glasses, and that's me :-).

> About 30 years ago, probes were launched into a harsh environment
> with no hope of applying any hands-on servicing or manual re-boot,
> and they are still out there working beyond the solar system.

Er, no.

1)  Their programs run in RAM/programmable memory.  They literally
upload entire programs to do course changes/sensor scan runs etc.
(incidentally, Voyager uses an RCA 1802 CMOS processor, one of the
first processors I cut my teeth on, known in folklore for its SEX
instruction (SEt X register)).

2)  They use watchdog timers, so if the processor does lock up they
can not only initiate a reboot, but also fall back to a standby
program in case the uploaded program was faulty.

3)  They are engineered _well_.  The Radio Amateurs (hi Steve F!)
got great service out of one of their Oscar satellites as a
repeater even though its brains were fried during insertion into
orbit - it fail-safed into a usable working mode.

> What has happened to the art of software development since then?!

"The bits have gotten wider, but not any smarter."  Actually, "time
to market" may play a significant factor.  No-one wants old software
(he says, as one of his side projects is to resurrect his old '286
Coherent box).


Regards,
  Daryl Tester

-- 
LinuxSA WWW: http://www.linuxsa.org.au/  IRC: #linuxsa on irc.linux.org.au
To unsubscribe from the LinuxSA list:
  mail linuxsa-request@linuxsa.org.au with "unsubscribe" as the subject