The gdbm family of functions in maildrop provides access to GDBM/DB databases - simple database files. The gdbm family of functions provide a way of quickly storing and looking up key/data pairs.
You can use any program to create GDBM/DB database files. makedat is a quick utility to create GDBM or DB files from plain text files.
The system administrator selects whether maildrop uses GDBM or DB database files and whether makedat creates GDBM or DB database files as well.
The makedat command may not be available to you. GDBM/DB support in maildrop is optional, and the system administrator may choose not to install GDBM/DB support and the makedat command.
To see whether GDBM or DB support is being used, run the command "maildrop -v".
The textfile argument to makedat is a plain text file containing key/value pairs. Each line in the text file contains a key value, followed by a tab and a data value. The data value may be omitted, which defaults to "1". For example, the following three lines:
Three key/value pairs are created: example.com, value "1"; domain.com, value "ok", and "foo.domain.com", value "bad".
Empty lines in textfile, and lines starting with the # character, are ignored.
textfile can be "-", in which case standard input is used.
gdbmfile is the GDBM/DB file to create. If this file exists, its existing contents are replaced.
tmpfile is a name of a temporary file in the same directory as gdbmfile. tmpfile is used by makedat to create the GDBM file, then tmpfile is renamed to gdbmfile.
This approach foregoes any need for locking in order to be able to dynamically update GDBM/DB files used by maildrop's gdbm functions. However, makedat does not use any locks on tmpfile, so multiple instances of makedat using the same tmpfile are prohibited.
The -cidr flag specifies that the key is an IP netblock in CIDR notation. This flag requires the Net::CIDR Perl module to be installed separately. Download Net::CIDR from http://www.cpan.org.
There are historical reasons why database functions in maildrop are called gdbm functions. The initial implementation used GDBM functions exclusively. The ability to use the DB library instead of the GDBM library has been added later.
Takes blacklist, and creates /etc/mail/blacklist.dat, using /etc/mail/blacklist.tmp as a temporary file.