DNS and BIND 5th Edition_5

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DNS and BIND 5th Edition_5 DNS & BINDThere are more options to h2n than weve shown here. For the complete list of options, youll have to look atthe manpage.Of course, a few kinds of resource records arent easy to generate from /etc/hosts − the necessary data simplyarent there. You may need to add these records manually. But since h2n always rewrites db files, wont yourchanges be overwritten?h2n provides a back door for inserting this kind of data. Put these special records in a filenamed spcl.DOMAIN, where DOMAIN is the domain name of your zone. When h2n finds this file, it willinclude it within the database files by adding the line: $INCLUDE spcl.DOMAINto the end of the db.DOMAIN file. (The $INCLUDE directive is described later in this chapter.) For example,the administrator of movie.edu may add extra MX records into the file spcl.movie so that users can mail tomovie.edu directly instead of sending mail to hosts within movie.edu. Upon finding this file, h2n would putthe line: $INCLUDE spcl.movieat the end of the database file db.movie.7.2.6 Keeping db.cache CurrentAs explained in Chapter 4, the db.cache file tells your server where the servers for the root zone are. It mustbe updated periodically. The root name servers do not change very often, but they do change. A good practiceis to check your db.cache file every month or two. In Chapter 4, we told you to get the servers by ftping toftp.rs.internic.net. And thats probably your best method to keep current.If you have on your system a copy of dig, a utility that works a lot like nslookup and is included in theBIND distribution, you can retrieve the current list of roots just by running: % dig @a.root−servers.net . ns > db.cache7.1 BIND Name Server 7.3 Organizing Your FilesSignals[ Library Home | DNS & BIND | TCP/IP | sendmail | sendmail Reference | Firewalls | Practical Security ]7.2.6 Keeping db.cache Current 213 DNS & BIND Chapter 7 Maintaining BIND7.3 Organizing Your FilesWhen you first set up your domain, organizing your files was simple − you put them all in a single directory.There was one configuration file and a handful of db files. Over time, your responsibilities grew. Morenetworks were added. Maybe a few subdomains were started. You started backing up zones for other sites.After a while, an ls of your name server directory no longer fits on a single screen. Its time to reorganize.BIND has a few features that will help with your organization.The configuration file for a 4.9 or later server can have a control entry, called include, which allows you toinsert a new configuration file into the current configuration file. This allows you to take a very largeconfiguration file and break it into smaller pieces. The database files (for all BIND versions) allow twocontrol entries: $ORIGIN and $INCLUDE. $ORIGIN changes the origin, and $INCLUDE inserts a new fileinto the current file. The database control entries are not resource records; they facilitate the maintenance ofDNS data. In particular, these statements make it easier for you to divide your domain into subdomains: theyallow you to store the data for each subdomain in a separate database file.7.3.1 Using Several DirectoriesOne way to organize your db files is to store them in separate directories. If your server is a primary masterfor several sites (both forward and reverse maps), you could store each sites db files in its own directory.Another division might be to store all the primary master files in one directory and all the slave backup filesin a different directory. Lets look at what the version 4 configuration file might look like if you chose theprimary/slave division: directory /usr/local/named ; ; These files are not specific to any zone ; cache . db.cache primary 0.0.127.in−addr.arpa db.127.0.0 ; ; These are our primary zone files ; primary movie.edu primary/db.movie primary 249.249.192.in−addr.arpa primary/db.192.249.249 primary 253.253.192.in−addr.arpa primary/db.192.253.253 ; ; These are our slave zone files ; secondary ora.com 198.112.208.25 slave/bak.ora secondary 208.112.198.in−addr.arpa 198.112.208.25 slave/bak.198.112.208Heres the same configuration file in version 8 format: 214 ...