Date: Wed, 15 Apr 1998 10:40:33 -0700 From: "Eric A. Davis" <edavis@nas.nasa.gov> To: sfarrell+lists@farrell.org Cc: Dan Nelson <dnelson@emsphone.com>, "Matthew N. Dodd" <winter@jurai.net>, Eivind Eklund <eivind@yes.no>, edavis@shark.nas.nasa.gov, freebsd-hackers@FreeBSD.ORG Subject: Re: how to add new system calls... Message-ID: <199804151740.KAA26082@shark.nas.nasa.gov> In-Reply-To: sfarrell%2Blists's message of 15 Apr 1998 12:07:36 -0500.<87hg3vko87.fsf@phaedrus.uchicago.edu>
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On 15 Apr 1998 12:07:36 -0500 sfarrell+lists@farrell.org wrote
>Dan Nelson <dnelson@emsphone.com> writes:
>
>> In the last episode (Apr 15), Matthew N. Dodd said:
>> > On Wed, 15 Apr 1998, Eivind Eklund wrote:
>> > > YES! I've been missing this since I left my Amiga 5 years ago!
>> > >
>> > > Does the above imply watching for changes in directories, too? Ie,
>> > > file added to directory, notification sent...
>> > >
>> > > What level of notification? Do you get information saying 'file so
>> > > changed atime to XXX'/'file XXX added to directory', or just a flag
>> > > saying 'event so happened on descriptor so'?
>> >
>> > Mmm... tripwired
>>
>> Sort of like tripwire, but in real time. The Amiga has a feature where
>> you could monitor a file or directory for changes. Imagine cron
>> getting a signal when /var/cron/tabs changes. Or any other daemon that
>> has a config file. There's a description of the function (but not the
>> assosicated structures unfortunately) at
>
>Also applicable, perhaps, to GUI items like file managers so they do
>not need to poll the directory.
>
Let me tell you what we are doing here at the NAS. We have approx 200 users
publishing web pages. All web pages are located on a central 'build' box
were the users do their editing. This 'build' box is a powerful SGI system
running IRIX 6.2. The IRIX kernel has a facility called imon & fam that
allows real time monitoring of the filesystem.
I wrote an application that monitors _all_ the web files. There are over
xxxx files and directories that are being monitored. This has worked out
_extremely_ well for us. Any time a change occurs within these filesystems
my application immediately notices it and copies/updates/makes the changes
on our actual server located in a DMZ. This is great because using this
paradigm we can also manage the ownership and permissions of the files on
our servers.
For the updates between our 'build' box and our servers we have written
a fast transfer client/server app that uses digital certificates and SSL.
I realize this description isn't for this kernel list but I just wanted
let you all know the usefulness of such a kernel facility. Besides, don't
we all look for alternatives to NFS. ;-)
- e
--
Eric Allen Davis Network Engineer
edavis@nas.nasa.gov NASA Ames Research Center
Voice: (415)604-2543 NAS Systems Division
Pager: (415)428-6931 http://www.nas.nasa.gov/~edavis
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