syncing data across machines automatically

[Giles Orr]

Sorry for the reply-to-self, I hope it makes sense in context.

On 4/11/08, Giles Orr <gilesorr-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> I have a friend who wants to synchronize data across three machines:
> two Intel-based, one running Fedora, one running Ubuntu, and the final
> machine running Solaris 10 on an Ultra 60.  I initially recommended
> rsync which I use to update my domain hosting site.  But I'm not sure
> rsync is the answer when data is generated on all three machines and
> will preferably be synced to the other two on a regular basis
> automatically (cron job).  How to do this securely is beyond me.  The
> friend is in the state of Georgia and I won't be laying hands on the
> machines myself: but he's quite good at reading manuals and working
> with computers.  However we're in dire need of pointers.  Thanks!

I remember now that I used to use NFS and sync several machines to a
central server, but that was over a small personal network and
probably isn't a good idea on a public network (he's on a campus).

Lennart suggested rsync-over-ssh, and Anthony suggested
unison-over-ssh ... these are the two ideas I suggested to my friend.
It seems I'm mis-characterizing the problem (or not explaining where
my understanding is breaking down): I lock up when we get to the "cron
job" part of this.  How do you automate a job like this over ssh?
Three servers, does he have to sit down, login, enter an ssh
passphrase, and log back out every time a machine is (re)booted?  I
think this is what's causing me issues.  Or do you use an ssh key
without a passphrase?  Can that be done safely?

Sorry I didn't explain the issue more clearly.  At least it seems I
was on to the right tools.

-- 
Giles
http://www.gilesorr.com/
gilesorr-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
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