About WEBDNS

WEBDNS is a an World Wide Web facility for editing Internet Domain
Name System master files. It is implemented as a perl script.

How It Works

Every time you make a request of WEBDNS, it uses the named.boot file
on the machine on which it is running to find all the DNS master files
for which the machine is a primary server. It then effectively reads
in all the master files. If the request is to view some data or build
a form, WEBDNS extracts and presents the relevant data. If the request
is a post, WEBDNS checks the contents of the post for consistency,
updates its internal data structures, and then dumps out new versions
of all the master files.

The dbm File Cache

Because it takes so long to read and write the master files, WEBDNS
maintains a cache of the data in random-access dbm files. Whenever it
is about to read in all the master files, it really first checks if
the master files have been modified since WEBDNS last regenerated
them, and if not, it uses its dbm files instead. This makes getting
data a lot faster.

By default, WEBDNS will always regenerate the DNS master files every
time an edit is made. This can take a long time. You can disable the
regeneration of DNS master files by choosing the ``Just update dbm
files'' option, which appears above the ``Submit'' button on update
forms. If you are going to submit many changes in a row, you will be
done sooner if you choose the ``Just update dbm files'' option in all
but your last edit. Then, when you submit your last change with the
option ``Update dbm files, then regenerate DNS master files from dbm
files,'' all the changes you made to the dbm files will be reflected
in the new DNS master files.

Be aware, however, that if there ever is any ambiguity between changes
to the DNS master files and changes to dbm files, WEBDNS always defers
to the DNS master files. For example, if Joe uses WEBDNS to make a
change, but tells WEBDNS to only update its dbm files, and Sue changes
a DNS master file directly by editing it with a text editor, WEBDNS
would not regenerate the DNS master files from its dbm files, which
would cause Sue's edit to be lost. Instead, the next time WEBDNS runs,
it would notice that the DNS master files had been updated by Sue, and
it would rebuild its dbm files from the DNS master files, resulting in
the loss of Joe's change, even if he and Sue made changes to two
different hosts.

Due to the hazards of this ambiguity resolution policy, if WEBDNS is
used at all to make updates to the DNS master files, the best DNS
master file administration strategy is to use WEBDNS as much as
possible, with frequent regenerations of the DNS master files, and to
avoid changes to the DNS master files by other means.

The Author

WEBDNS was written by Chris Lindblad while doctoral student at the MIT
Laboratory for Computer Science. He wrote it to learn perl and to
avoid working on his thesis. You can send comments to him at
cjl@lcs.mit.edu.