Datasheet

“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 465 — #491
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Linux in the Network
Line 2: This is where the SOA (start of authority) control record begins:
The name of the domain to administer is world.cosmos in the
first position. This ends with a ., because otherwise the zone
would be appended a second time. Alternatively, @ can be en-
tered here, in which case the zone would be extracted from the
corresponding entry in /etc/named.conf.
After IN SOA is the name of the name server in charge as
master for this zone. The name is expanded from gateway to
gateway.world.cosmos, because it does not end with a ..
An e-mail address of the person in charge of this name server
follows. Because the @ sign already has a special meaning, . is
entered here instead. For [e-mail] the entry must
read root.world.cosmos.. The . must be included at the end
to prevent the zone from being added.
The ( includes all lines up to ) into the SOA record.
Line 3: The serial number is an arbitrary number that is increased each
time this file is changed. It is needed to inform the secondary name
servers (slave servers) of changes. For this, a ten-digit number of the
date and run number, written as YYYYMMDDNN, has become the
customary format.
Line 4: The refresh rate specifies the time interval at which the sec-
ondary name servers verify the zone serial number. In this case,
one day.
Line 5: The retry rate specifies the time interval at which a secondary
name server, in case of error, attempts to contact the primary server
again. Here, two hours.
Line 6: The expiration time specifies the time frame after which a
secondary name server discards the cached data if it has not regained
contact to the primary server. Here, it is a week.
Line 7: The last entry in the SOA record specifies the negative
caching TTL — the time for which results of unresolved DNS
queries from other servers may be cached.
Line 9: The IN NS specifies the name server responsible for this domain.
gateway is extended to gateway.world.cosmos because it does
not end with a .. There can be several lines like this — one for the
primary and one for each secondary name server. If notify is not
465SUSE LINUX Enterprise Server