Web host forum - Let’s look at each statement individually. The directory
Let’s look at each statement individually. The directory keyword tells named that all filenames referred to later in this file, zone files for example, are located in the /var/named directory. This saves a little typing. The primary keyword shown in this example loads information into named. This information is taken from the master files specified as the last of the parameters. These files represent DNS resource records, which we will look at next. In this example, we configured named as the primary name server for three domains, as indicated by the three primary statements. The first of these statements instructs named to act as a primary server for vbrew.com, taking the zone data from the file named.hosts. The cache keyword is very special and should be present on virtually all machines running a name server. It instructs named to enable its cache and to load the root name server hints from the cache file specified (named.ca in our example). We will come back to the name server hints in the following list. Here’s a list of the most important options you can use in named.boot: directory This option specifies a directory in which zone files reside. Names of files in other options may be given relative to this directory. Several directories may be specified by repeatedly using directory. The Linux file system standard suggests this should be /var/named. primary This option takes a domain name and filename as an argument, declaring the local server authoritative for the named domain. As a primary server, named loads the zone information from the given master file. There will always be at least one primary entry in every boot file used for reverse mapping of network 127.0.0.0, which is the local loopback network. secondary This statement takes a domain name, an address list, and a filename as an argument. It declares the local server a secondary master server for the specified domain. A secondary server holds authoritative data on the domain, too, but it doesn’t gather it from files; instead, it tries to download it from the primary server. The IP address of at least one primary server thus must be given to named in the address list. The local server contacts each of them in turn until it successfully transfers the zone database, which is then stored in the backup file given as the third argument. If none of the primary servers responds, the zone data is retrieved from the backup file instead. named then attempts to refresh the zone data at regular intervals. This process is explained later in connection with the SOA resource record type. cache This option takes a domain name and filename as arguments. This file contains the root server hints, which is a list of records pointing to the root name servers. Only NS and A records will be recognized. The domain should be the root domain name, a simple period (.). This information is absolutely crucial to named; if the cache statement does not occur in the boot file, named will not develop a local cache at all. This situation/lack of development will severely degrade performance and increase network load if the next server queried is not on the local net. Moreover, named will not be able to reach any root name servers, and thus won’t resolve any addresses except those it is authoritative for. An exception from this rule involves forwarding servers (see the forwarders option that follows). forwarders This statement takes a whitespace-separated list of addresses as an argument. The IP addresses in this list specify a list of name servers that named may query if it fails to resolve a query from its local cache. They are tried in order until one of them responds to the query. Typically, you would use the name server of your network provider or another well-known server as a forwarder.