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<H2><A NAME="SECTION008210000">The named.boot File</A></H2>
<P>
The named.boot file is generally very small and contains little
else but pointers to master files containing zone information, and
pointers to other name servers. Comments in the boot file start with a
semicolon and extend to the next newline.
Before we discuss the format of named.boot in more detail, we
will take a look at the sample file for vlager given in
figure-<A HREF="node87.html#resolvfignamedboot"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A>.<A HREF="footnode.html#3691"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<P><A NAME="3692"></A><BR>
<STRONG>Figure:</STRONG>
<A NAME="resolvfignamedboot"></A>
The named.boot file for vlager.
<pre>
;
; /etc/named.boot file for vlager.vbrew.com
;
directory /var/named
;
; domain file
;---------------------------------------------------
cache . named.ca
primary vbrew.com named.hosts
primary 0.0.127.in-addr.arpa named.local
primary 72.191.in-addr.arpa named.rev
</pre>
<P>
The cache and primary commands shown in this
example load information into named. This information is taken
from the master files specified in the second argument. They contain
textual representations of DNS resource records, which we will look at
below.
<P>
In this example, we configured named as the primary name server
for three domains, as indicated by the primary statements
at the end of the file. The first of these lines, for instance, instructs
named to act as a primary server for vbrew.com, taking the
zone data from the file named.hosts. The directory
keyword tells it that all zone files are located in /var/named.
<P>
The cache entry is very special and should be present on
virtually all machines running a name server. Its function is
two-fold: it instructs named to enable its cache, and to load
the <em>root name server hints</em> from the cache file specified
(named.ca in our example). We will come back to the name server
hints below.
<P>
Here's a list of the most important options you can use in
named.boot:
<dl>
<dt> directory <dd>This specifies a directory in which zone files reside. Names
of files may be given relative to this directory. Several
directories may be specified by repeatedly using directory.
According to the Linux filesystem standard, this should be
/var/named.
<dt> primary <dd>This takes a domain name and a file name 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.
Generally, there will always be at least one primary
entry in every boot file, namely for reverse mapping of net-
work 127.0.0.0, which is the local loopback network.
<dt> secondary <dd> This statement takes a domain name, an address list, and a
file name as an argument. It declares the local server a sec-
ondary master server for the domain specified.
A secondary server holds authoritative data on the
domain, too, but it doesn't gather it from files, but tries to
download it from the primary server. The IP address of at
least one primary server must thus be given to named in the
address list. The local server will contact 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 will then attempt to refresh the zone data at regu-
lar intervals. This is explained below along in connection
with the SOA resource record type.
<dt>cache <dd>This takes a domain and a file name as arguments. This file
contains the root server hints, that is a list of records
pointing to the root name servers. Only NS and A records will
be recognized. The domain argument is generally the root
domain name ``.''.
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 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 it won't resolve
any addresses except those it is authoritative for. An excep-
tion from this rule is when using forwarding servers (cf. the
forwarders option below).
<dt>forwarders <dd>This statement takes an address list 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.
<dt> slave <dd>This statement makes the name server a slave server. That is,
it will never perform recursive queries itself, but only for-
wards them to servers specified with the forwarders statement.
</dl>
There are two options which we will not describe here, being
sortlist and domain. Additionally, there are two
directives that may be used inside the zone database files. These are
$INCLUDE and $ORIGIN. Since they are rarely
needed, we will not describe them here, either.
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<P><ADDRESS>
<I>Andrew Anderson <BR>
Thu Mar 7 23:22:06 EST 1996</I>
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