How to synchronize local svn with official svn?

[y.volta]

hi all,

    I have a question about using svn: how can i synchronize the local copy 
with the local svn and official svn? 
for examle:

    1. i checkout the official grub2 from SA 
(svn://svn.sv.gnu.org/grub/trunk/grub2) to LD (/home/grub2);

    2. and then, i create a local site to host the grub2 - SB ( i.e. 
svn://local/grub2 ), 
    
    now, i can 'Relocate' LD's url to SB, and 'Update' LD to SB. here, i get a 
local svn copy, and can do anythings but the synchronization from SA.

    so, how to synchronize local svn with official svn? any suggestion?

Y.Volta