turandot
I am using rsync on a separate Linux server to regularly backup SME 7.5.1, the ideas are described here http://www.howtomonster.com/2007/08/08/how-to-sync-data-between-2-servers-automatically/ All relevant paths are backuped including relevant Samba files.
Does that method correctly backup the mysql databases ?
The built in SME backup routines dump all the mysql dbs to a file that is included in the standard backup.
Is it possible to directly replicate back 7.5.1 data and especially Samba configuration files into SME 8.0?
You can reliably use one of the built in SME backup to USB routines.
Using the admin console do a immediate backup to an attached USB drive (formatted ext3).
Then during the SME8b7 install procedure you will be asked to do a one off restore from USB, connect the USB drive and select that option.
Then as with all supported SME backup/restore procedures (including Affa), reinstall any contribs, making sure they are compatible with SME8.x
You should really review any contribs you have installed on SME7.5.1 to ensure they are compatible with SME8b7 BEFORE you perform the upgrade (see the wiki).
If there is a contrib that is vital to you, you may want to hold off from doing the upgrade until a compatible contrib is released, otherwise uninstall the contrib before doing the backup, and do not reinstall that contrib on SME8b7.