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NAME    [Toc]    [Back]

       resolv.conf - Resolver configuration file

SYNOPSIS    [Toc]    [Back]


DESCRIPTION    [Toc]    [Back]

       The  resolver  is  a  set  of  routines  in  the C library
       (resolver(4)) that provide access to the  Internet  Domain
       Name  System.   The  resolver  configuration file contains
       information that is read  by  the  resolver  routines  the
       first  time  they  are  invoked by a process.  The file is
       designed to be human readable and contains a list of  keywords
  with  values that provide various types of resolver

       The keyword and value must appear on a  single  line,  and
       the keyword (for example, nameserver) must start the line.
       The value follows the keyword, separated by  white  space.
       For example: keyword value

       The file format is as follows: nameserver Address

       Internet  address  (in dot notation) of a name server that
       the resolver should query.  Up to MAXNS (currently 3) name
       servers may be listed, one per keyword.  If there are multiple
 servers, the resolver library queries  them  in  the
       order  listed.   If no nameserver entries are present, the
       default is to use the name server on  the  local  machine.
       (The  algorithm  used  is to try a name server, and if the
       query times out, try the next, until out of name  servers,
       then  repeat  trying  all the name servers until a maximum
       number of retries are made).  domain DomainName

       Local domain name.  Most queries  for  names  within  this
       domain  can  use short names relative to the local domain.
       If no domain entry is present, the  domain  is  determined
       from  the  local  host name returned by gethostname(); the
       domain part is taken to  be  everything  after  the  first
       (dot).   Finally,  if  the  host  name  does not contain a
       domain  part,  the  root  domain   is   assumed.    search
       Domain_Name1 DomainName2 ...

       Search list for host-name lookup.  Up to six domains (separated
 by spaces or tabs) with a total of  256  characters
       can  be  specified.   If  no  search entry is present, the
       search list consists of the local domain name.

       Most 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, and that queries will time out if no server
       is available for one of the domains.

       You  can also specify a search list on a per-process basis
       by specifying the LOCALDOMAIN  environment  variable.  See

       The domain and search keywords are mutually exclusive.  If
       more than one instance of these keywords is  present,  the
       last  instance will override.  options allow_special all |
       { \char }

       Option for defining valid characters in hostnames.   Specify
  all  to  disable hostname checking (allow all characters)
 or define a set of valid characters by using  the  {
       \char  }  syntax,  where char is the character you want to
       allow.  For example, you can allow the  semicolon,  underscore,
 and colon characters by using { \; \_ \: }.

       Disabling hostname checking altogether is not recommended.
       By default, the allow_special option is not set and strict
       hostname checking is enforced.  options ndots:n

       Option  for  hostname lookup.  The n specifies the minimum
       number of dots a name must contain in order  for  resolver
       to  look  up  the name as given.  If the lookup fails, the
       search list (if specified) is applied. The range for n  is
       from 0 to 15.  If no options entry is present, the minimum
       number of dots is 1.

       You can also specify the number of dots on  a  per-process
       basis  by  using the RES_OPTIONS environment variable. See

CAUTIONS    [Toc]    [Back]

       Any white space entered  after  the  domain  name  is  not
       ignored but is interpreted as part of the domain name.

SEE ALSO    [Toc]    [Back]

       Commands: named(8)

       Functions: gethostbyname(3), resolver(4)

       Files: hostname(5)

[ Back ]
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