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

Andrea Venturoli ml.diespammer at
Wed Feb 14 10:18:17 UTC 2007

Olaf Greve wrote:

> 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...

I guess you might have heard of ggated (8) & Co. This is quite different 
from rsync and might or might not be suited to your needs and 
configuration. It's more like ghosting in some way and you'll need a 
dedicated partition for our data.
Also, AFAIK, you should not mount your data unless you know the other 
server failed or both are mounting this data read-only.
I never tested this myself, anyway.

What is best for you depends much on how you access your data. Is it 
read-only or read/write?

> Also, I'd like to be able to 
> (safely!) automatically synchronise users and groups that I may 
> add/change/delete on the live server.

I'm using OpenLDAP and nss_ldap for that. Works very well, in that 
syncronization is virtually immediate.
There are some caveats and this will introduce another possible point of 
failure, though.

> Regarding the data, the machine is mainly used as a webserver, running 
> PHP, MySQL and some other things.

WRT webserver data, it's just plain files, so it falls in the previous 
case. You should look for application level replication for databases.
I don't think PHP matters, but I can't really tell without knowing what 
you really have. Same goes for "some other things".

> 1) Is rsync a good way to go, or are there better ways to do this?

See above, might be, might be not.

> 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)?

See above for user and groups; home directories again fall into the 
filesystem part.


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