Red Hat ENTERPRISE LINUX 4.5.0 Reference Manual page 249

• — Start Of Authority resource record, proclaims important authoritative information about
SOA
a namespace to the nameserver.
Located after the directives, an
The following example shows the basic structure of an
@ IN SOA <primary-name-server><hostmaster-email> (
<serial-number><time-to-refresh><time-to-retry><time-to-expire><minimum-TTL>
)
The symbol places the
@
set) as the namespace being defined by this
primary nameserver that is authoritative for this domain is the
directive, and the email of the person to contact about this namespace is the
<hostmaster-email>
The
<serial-number>
altered to indicate it is time for
the numerical value slave servers use to determine how long to wait before asking the master
nameserver if any changes have been made to the zone. The
numerical value used by the slave servers to determine if it is using outdated zone data and
should therefore refresh it.
The
<time-to-retry>
length of time to wait before issuing a refresh request in the event the master nameserver is
not answering. If the master has not replied to a refresh request before the amount of time
specified in the
<time-to-expire>
an authority for requests concerning that namespace.
The
<minimum-TTL>
information.
When configuring BIND, all times are specified in seconds. However, it is possible to use
abbreviations when specifying units of time other than seconds, such as minutes (
( ), days ( ), and weeks (
H D
shows an amount of time in seconds and the equivalent time in another format.
Seconds
60
1800
3600
10800
21600
43200
86400
resource record is the first resource record in a zone file.
SOA
directive (or the zone's name, if the
$ORIGIN
directive.
directive is a numerical value incremented every time the zone file is
to reload the zone. The
named
directive is a numerical value used by slave servers to determine the
directive elapses, the slave servers stop responding as
directive is the quantity of time other nameservers cache the zone's
). The table in Table 12.1, "Seconds compared to other time units"
W
Zone File Resource Records
resource record:
SOA
resource record. The hostname of the
SOA
<primary-name-server>
<time-to-refresh>
<serial-number>
Other Time Units
1M
30M
1H
3H
6H
12H
1D
directive is not
$ORIGIN
directive is
directive is a
), hours
M
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