Good synchronisation strategies (especially for the users and groups)?

Olaf Greve o.greve at
Wed Feb 14 09:53:17 UTC 2007

Hi all,

I hope someone can give me some good advice regarding synchronisation 
strategies between two (very) different FreeBSD installations.

My live server runs FreeBSD 5.4 release AMD-64, and my fallback server 
runs FreeBSD 6.2 release i386.

The drive sizes do not match eiter, as the live machine has an U320 RAID 
10 array, with an array size of 73 Gb, and the fallback machine is 
'lighter' in this respect too, having only a U160 RAID 1 array with an 
array size of 36 Gb. I realise that at present the fallback machine has 
half the HDD storage space of the live server, but that's no problem (as 
the live server's storage space is only used for some 10% or so).

Obviously, ghosting images is no option. ;)

Previously I had set up (through cron) a nightly rsync strategy, (in 
combination with some shell scripts I wrote to directly update the DB, 
etc.) that took care of most of the synchronisation. Rsync was only 
allowed from the fallback's machines' (local) IP address, and the two 
machines were connected through a cross-wire cable with nothing in 
between. The server part of that is still configured, and the client 
part can be reconstructed, if necessary.

However, I seem to recall (not sure, anymore though) having heard and/or 
read (here, perhaps?) that there are better ways to synchronise than 
using rsync...

Soooo, now that the time has arrived to setup a synchronisation 
strategy, I can either recreate an rsync strategy, or choose something 
else (if there are better alternatives). Also, I'd like to be able to 
(safely!) automatically synchronise users and groups that I may 
add/change/delete on the live server.

Regarding the data, the machine is mainly used as a webserver, running 
PHP, MySQL and some other things. For me, it is totally fine if the 
various versions of the installed software are not exactly the same, 
just as long as I can at least synchronise the data itself in a viable way.

Therefore, I hope someone can answer the following questions, and/or 
perhaps point me to some good reading material on the matter:
1) Is rsync a good way to go, or are there better ways to do this?
2) Regarding synching of user and group data: are there special ways to 
do this (i.e. including automatic creation of homedirectories etc.), or 
does one simply manually have to sync the users and groups files (and 
the user directories)?


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