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System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP)

The hosts File

The hosts file contains all the data about the machines in the local zone. The name of this file is specified in the boot file. To avoid confusion with /etc/hosts, name the file something other than hosts, for example, you could name these files using the pattern db.domain. Using that nomenclature, the host files for the doc.com and sales.doc.com domains might be db.doc and db.sales.

Setting Up the hosts File

The hosts file contains all the data about every machine in your zone. If a zone covers more than one domain, all machines in all the domains covered by the zone are listed in the zone's host file. See Setting Up the hosts File.

Note –

The name hosts is a generic name indicating the file's purpose and content. But to avoid confusion with /etc/hosts, you should name this file something other than hosts. If you have more than one zone, each zone must have its own hosts file and each of these zone hosts files must have a unique name. For example, if your DNS domain is divided into doc.com and sales.doc.com zones, you could name one hosts file db.doc and the other sales.db.doc.

There must be a separate, uniquely named, hosts file for each zone. If you have more than one zone, each zone's host file must include information about the master (master and slave) servers of the other zones, as described in Example 5–16.

Example 5–16 Sample hosts File


;
; SOA rec
doc.com.  IN SOA sirius.doc.com. sysop.centauri.doc.com. (
                 1997071401       ;  serial number (YYYYMMDD##)
                      10800       ;  refresh every 3 hours
                      10800       ;  retry every 3 hours
                      604800      ;  expire after a week
                      86400 )     ;  TTL of 1 day
; Name Servers
doc.com.                   IN  NS  sirius.doc.com.
sales.doc.com.             IN  NS  altair.sales.doc.com.
; Addresses
localhost.                 IN  A  127.0.0.1
 
sirius                    IN  A  192.168.6.1
rigel                     IN  A  192.168.6.112
antares                   IN  A  192.168.6.90
polaris                   IN  A  192.168.6.101
procyon                   IN  A  192.168.6.79
tauceti                   IN  A  123.45.6.69
altair.sales.doc.com.     IN  A   111.22.3.4
; aliases
durvasa                   IN  CNAME sirius.doc.com.
dnsmastr                  IN  CNAME sirius.doc.com.
dnssales                  IN  CNAME altair.sales.doc.com.

A hosts file usually contains these elements: