*.tdb files are not human readable. They are written in a binary format. “Why not ASCII?”, you may ask. “After all, ASCII configuration files are a good and proven tradition on UNIX.” The reason for this design decision by the Samba Team is mainly performance. Samba needs to be fast; it runs a separate smbd process for each client connection, in some environments many thousands of them. Some of these smbds might need to write-access the same *.tdb file at the same time . The file format of Samba's *.tdb files allows for this provision. Many smbd processes may write to the same *.tdb file at the same time. This wouldn't be possible with pure ASCII files.