[Samba] importing SID from samba PDC

[baiocco.f at filottrano.bcc.it]

To import the SID from a Samba PDC from a Samba BDC I user the command

smbpasswd -S -r PDC

This command must be executed when the smb service on the BDC is running or not?

If I shut down the BCD when restarting it the SID must be reimported from the
PDC?

The secret.tdb is recreated at any time I start samba?

Thanks in advance!!