To simply use an existing network share to backup your data, use this:
# sudo ditto -V --rsrc SRC-DIR /Volumes/NETWORK_DISK
where SRC-DIR is what you want copied, and NETWORK_DISK is the name of the network file system that you have mounted.
In order to set up an encrypted connection, you will need Administrator privileges on the Linux server and your Mac client. As I document it here, this will BREAK any other SMB connections! So you might want to do this only as a temporary measure.
If you're still reading... my Samba setup on the Linux server...
/etc/samba/smb.conf:
[global]
workgroup=WORKGROUP
hosts allow = 127.0.0.1
security = user
[backup]
path = /path/to/large/disk
writeable = yes
only user = yes
valid users = backup
Then I create a user called "backup" via the smbpasswd command on my Linux box:
# smbpasswd -a backup
New SMB password:
Retype new SMB password:
Start your samba server; I typed # /etc/init.d/samba start to start mine. On the Macintosh, you need to set up an SSH tunnel to encrypt the connection to your SAMBA server. As I document it here, this will BREAK any other SMB connections! So you might want to do this only as a temporary measure.
Macintosh client SSH Setup:
# sudo nohup ssh -2 -q -f -N -g -L 139:127.0.0.1:139 root@linux-server
Now in the Finder, you can add a Connection to the following share: smb://localhost/backup. See, that's the real trick -- you let SSH tunnel a connection to the SMB port on your Linux server to a local port on your macintosh. Then you tell the Finder to connect to that (local) port -- that's why you use "localhost" as the server name.
We jump through all these hoops because for Linux servers, the most reliable network server setup seems to be Samba. And I wanted to encrypt the data stream between the computers. Note: It is rather slow. After you get the share set up, you might just want to try a Finder copy: drag folders to the appropriate icon in the Finder. Or use psync.

