7.1 What About Signals?


DNS on Windows 2000, 2nd Edition
By Matt Larson, Cricket Liu
Table of Contents
Chapter 7.  Maintaining the Microsoft DNS Server

7.1 What About Signals?

Those of you familiar with the BIND name server know that it's possible to signal a running name server to perform certain tasks, such as rereading its configuration file or turning on debugging information. The Microsoft DNS Server has no exact analog to a BIND name server's signals, but you can still make it perform certain tasks while running. We'll go over the tasks possible using signals on a BIND name server and show how to accomplish the same thing (if possible) with the Microsoft DNS Server:

Restart the name server

You can signal a BIND name server to reread its configuration file and zone data files. There's no comparable Microsoft DNS Server command. If the server obtains its configuration information from the Registry (the default mode), this command isn't necessary: as you make configuration changes with the DNS console, they take effect immediately in the running name server. If the server is using a BIND-style boot file, you must stop and restart the server after making a change to the boot file. For more information on the server "boot method," see Appendix C.

Dump a copy of the name server's internal database to a file

A BIND server can dump its entire memory database of authoritative data, cached data, and root name server "hints" to a file. There's no direct Microsoft DNS Server equivalent, but you can come closeall this information is visible in the DNS console. To see authoritative data, just select the appropriate zone. By selecting the Cached Lookups folder, you can see the contents of the name server's cache as well as the list of root name servers it's using. [1]

[1] You can see the Cached Lookups folder only if the DNS console is showing the advanced view: select View figs/u2192.gif Advanced .

Dump name server statistics to a file

You can't dump the Microsoft DNS Server's usage statistics to a file, but you can view them from System Monitor (a Microsoft Management Console snap-in). Statistics are covered in detail at the end of this chapter.

Start/stop writing debugging information to a file

The Microsoft DNS Server can log several different kinds of debugging- related information to a file. This behavior is controlled from the Logging tab of the server properties window, where you can select the types of debugging information that should be logged.

Log all queries

As with a BIND server, you can also direct the Microsoft DNS Server to log individual queries processed . Use the Query option on the Logging tab.

The main thing you can do to a running Microsoft DNS Server is stop it and start it again. What happens when you stop and start the server? Remember that the name server answers queries from its in-memory database. This database includes three kinds of information: authoritative data (zones for which the server is a primary master or slave), cached data (answers from other name servers), and root name server "hints" (the list of root name servers from the root name server cache file, cache.dns ). When you stop the name server, this data is lost.

When you restart the server, it reloads the authoritative data from the zone data files on its disk. Zones for which the server is a primary master are loaded and not read again for the lifetime of the server process. (Of course, you can make a change to a primary zone with the DNS console and direct the server to write to the zone data file with Action figs/u2192.gif Update Server Data Files , but the server reads the zone data file only at startup.) Zones for which the server is a slave are also loaded from the zone data files. But for each zone, the server queries its master (usually the zone's primary master) for the SOA record to compare serial numbers . If the master's serial number is larger than the serial number in the zone just loaded from disk, the server performs a zone transfer.

The server also reads cache.dns at startup. In Chapter 4, we described how root name server information is used not directly, but as a "hint" to find the current list of root name servers: the server queries a root name server from cache.dns for the current list of root name servers, and the results are the first records in the cache. Remember, the cache is empty when the server starts up.


DNS on Windows 2000
DNS on Windows 2000
ISBN: 0596002300
EAN: 2147483647
Year: 2001
Pages: 154

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