Make sure that the AuthDBUserFile is stored
outside the document tree of the web server; do not put it in the
directory that it protects. Otherwise, clients will be able to
download the AuthDBUserFile.
In regards to compatibility, the implementation of
dbmopen in the Apache modules reads the string
length of the hashed values from the DB data structures, rather than
relying upon the string being NULL-appended. Some applications, such
as the Netscape web server, rely upon the string being NULL-appended,
so if you are having trouble using DB files interchangeably between
applications, this may be a part of the problem.
A perl script called dbmmanage is included with Apache. This program can be used to create and update DB-format password files for use with this module.