The resolver file (RESLVCNF.NET.SYS)
is an initialization file for the domain name resolver. It contains
information needed by the network to determine how to resolve a
domain name to an IP address. This file is read by the resolver
routines the first time they are invoked by a process.
To create the resolver file, perform the following steps:
Copy the sample file, RSLVSAMP.NET.SYS,
to RESLVCNF.NET.SYS.
Modify RESLVCNF.NET.SYS
using any ASCII editor so that it contains information about the
name servers, domain, and search order for your network. The keywords
included in the file are described under "Fields."
To modify an already existing RESLVCNF.NET.SYS
file, simply use your editor to update and save the existing file.
Fields
Each entry in the resolver file consists of a keyword followed
by a value separated by white space. The keyword and its associated
value must appear on a single line and the keyword must start the
line. Figure 12-1 “Sample Resolver Configuration File” shows an example
of a resolver file. Comment lines start with a pound sign (#).
- domain
Enter the local domain name. Most queries for names
within this domain can use short names relative to the local domain
name. If the host name does not contain a domain part, the root
domain is assumed. If more than one instance of the domain
keyword is present, the last instance will override.
The domain name is composed of labels, with each label separated
by a period. Each label must start with a letter or digit, and have
as interior characters only letters, digits, hyphens (-), or underbars
(_). A domain name may have any number of labels, but its total
length, including periods, is limited to 255 characters.
label[.label][...]
Domain names are not case sensitive.
- search
The search entry
is optional and indicates the order in which domains should be searched
for host name lookup. You should add a search
entry if users on this system commonly try to connect to nodes in
other domains. The search list is limited to six domains with a
total of 256 characters. If more than one instance of the search
keyword is present, the last instance will override.
Resolver queries will be attempted using each component of
the search path in turn until a match is found. Note that this process
may be slow and will generate a lot of network traffic if the servers
for the listed domains are not local. Note also that queries will
time out if no server is available for one of the domains.
- nameserver
Enter the IP address of a name server the resolver
should query. The address must be in dot format, with leading zeros
omitted and a period between each grouping. See example addresses
in Figure 12-1 “Sample Resolver Configuration File”.
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 | NOTE: It is very important that you omit the leading zeros
in the network addresses that you enter in the domain name resolver
files. If you enter leading zeros here, the domain name resolver
will interpret the numbers as octal numbers. |
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You can list up to three name servers, but you must use a
separate keyword entry for each. If there are multiple servers,
the resolver will query them in the order listed. If no nameserver
entries are present, the default is to use the HOSTS.NET.SYS
file.
If you have no server, do not add any nameserver
entries; the resolver will immediately revert to the HOSTS.NET.SYS
file.
Errors in the resolver file will be silently ignored by the
resolver routines.
Figure 12-1 Sample Resolver Configuration File
![[Sample Resolver Configuration File]](img/gfx51.gif)
