What does the entry valid users = @smbusers in the smb.conf file mean when used in a share section?

This parameter controls access based on user identity and group membership, not on the originating machine's hostname; host-based access control uses parameters like `hosts allow` or `hosts deny`.

The `valid users` parameter controls who can connect to the share, not the ownership of files created within it, which is determined by parameters such as `create mask` and `force group`.

The `@` prefix before a name in the `valid users` parameter denotes a Unix group, meaning that only users who are members of the 'smbusers' Unix group will be granted access to this specific share.

If the intent was to allow only a single user, the `@` symbol would not be used; `@smbusers` explicitly refers to a Unix group named 'smbusers'.