Samba ships with a little utility that helps the root user of your system to backup your *.tdb files. If you run it with no argument, it prints a usage message:

root# 

tdbbackup

 Usage: tdbbackup [options] <fname...>
 
 Version:3.0a
   -h            this help message
   -s suffix     set the backup suffix
   -v            verify mode (restore if corrupt)

Here is how I backed up my printing.tdb file:

root# 

ls

.              browse.dat     locking.tdb     ntdrivers.tdb printing.tdb
..             share_info.tdb connections.tdb messages.tdb  ntforms.tdb
printing.tdbkp unexpected.tdb brlock.tdb      gmon.out      namelist.debug  
ntprinters.tdb sessionid.tdb
 
root# 

tdbbackup -s .bak printing.tdb

 printing.tdb : 135 records
 
root# 

ls -l printing.tdb*

 -rw-------    1 root     root        40960 May  2 03:44 printing.tdb
 -rw-------    1 root     root        40960 May  2 03:44 printing.tdb.bak