samba - Mar 2001 - secrets.tdb in samba-2.2.0

I get:

dadecal@tramontana:~/sambaSource/samba-2.2.0-alpha2/source$
/usr/local/samba/bin/smbpasswd
Failed to open /usr/local/samba/private/secrets.tdb

What is secrets.tdb?What format should it have?
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Daniel de los Reyes
S2-Selling Soluciones
Valencia Spain
e-mail: dadecal@s2-selling.com
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