Trying to back up 10.4 server settings, you might run into this gross serveradmin bug:

machine:~ root# serveradmin settings all > all.sabackup
2008-09-01 14:34:43.994 serveradmin[12811] Exception in doCommand: *** -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)
serveradmin(12811,0xa000ed88) malloc: ***  Deallocation of a pointer not malloced: 0x15c3bc0; This could be a double free(), or free() called with the middle of an allocated block; Try setting environment variable MallocHelp to see tools to help debug

But luckily it's easy to work around with a little bit of shell:

for s in $(serveradmin list); do serveradmin settings $s >> all.sabackup; done

Save that as a Bash function and you're good to go.