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resolv.conf(5)

resolv.conf(5)                   File Formats                   resolv.conf(5)

NAME
       resolv.conf - resolver configuration

SYNOPSIS
       svc:/network/dns/client


       /etc/resolv.conf

DESCRIPTION
       The  resolver  is a set of routines that provide access to the Internet
       Domain Name System. See resolver(3RESOLV).


       resolv.conf is a configuration file that contains the 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 informa‐
       tion.


       The  configuration  used  by  the  resolver  is  managed  by SMF in the
       svc:/network/dns/client service. The resolver routines read  this  con‐
       figuration the first time they are invoked by a process.


       The  resolv.conf  file  is regenerated from the SMF properties when the
       service is started or refreshed.


       The file is designed to be human readable and contains a list  of  key‐
       words with values based on the SMF configuration.


       The  following  properties  are  supported  and contained in the config
       property group of the svc:/network/dns/client service.


       The following properties are single-valued or multi-valued:

       nameserver

           Specifies the IPv4 or IPv6 Internet address of a name  server  that
           the  resolver  is to query. Up to MAXNS name servers may be listed,
           one per property value.  See  <resolv.h>.  If  there  are  multiple
           servers,  the resolver library queries them in the order listed. If
           no name server entries are present, the  resolver  library  queries
           the  name server on the local machine. The resolver library follows
           the algorithm to try a name server until the query  times  out.  It
           then  tries  the  name  servers that follow, until each query times
           out. It repeats all the name servers until a maximum number of  re‐
           tries are made.


       domain

           Specifies the local domain name. Most queries for names within this
           domain  can use short names relative to the local domain. If no do‐
           main property is present, the domain is determined from  sysinfo(2)
           or  from  gethostname(3C).  (Everything after the first '.' is pre‐
           sumed to be the domain name.) If the host name does not  contain  a
           domain  part,  the root domain is assumed. You can use the LOCALDO‐
           MAIN environment variable to override the domain name.


       search

           The search list for host name lookup. The search list  is  normally
           determined  from  the local domain name. By default, it starts with
           the local domain name and may include additional parent domains. Up
           to MAXDFLSRCH domains will be used, as long  as  each  contains  at
           least  LOCALDOMAINPARTS  domain  labels.  See  <resolv.h>.  You can
           change the default behavior by listing the  desired  domain  search
           path, one domain per property value.

           Most resolver queries will be attempted using each component of the
           search  path  in  turn  until a match is found. This process may be
           slow and will generate a lot of network traffic if the servers  for
           the  listed  domains  are  not  local.  Queries will time out if no
           server is available for one of the domains.

           The search list is currently limited to six domains and a total  of
           256 characters.


       sortlist

           Allows  addresses  returned  by  the libresolv-internal  gethostby‐
           name() to be sorted. A sortlist is specified by IP address and pre‐
           fix length pairs. The prefix length is optional and defaults to the
           natural prefix length of the net. The IP address and optional  pre‐
           fix  length  pairs  are separated by slashes. Up to 10 pairs may be
           specified. For example:

             130.155.160.0/20 130.155.0.0



       options

           Allows certain internal resolver variables to be modified. The syn‐
           tax is


             option ...

           where option is one of the following:

           debug

               Sets RES_DEBUG in the _res.options field.


           usevc

               Sets RES_USEVC in the _res.options field to use TCP instead  of
               UDP for queries.


           use-vc

               Sets  RES_USEVC in the _res.options field to use TCP instead of
               UDP for queries. GNU libc alias for usevc.


           ndots:n

               Sets a threshold floor for the number of dots which must appear
               in a name given to res_query() before an initial absolute  (as-
               is)  query  is  performed.  See  resolver(3RESOLV). The default
               value for n is 1, which means that if there are any dots  in  a
               name,  the  name  is tried first as an absolute name before any
               search list elements are appended to it.


           timeout:n
           retrans:n

               Sets the amount of time the resolver will wait for  a  response
               from a remote name server before retrying the query by means of
               a  different  name  server. Measured in seconds, the default is
               RES_TIMEOUT. See <resolv.h>. The timeout and retrans values are
               the starting point for an exponential back off procedure  where
               the timeout is doubled for every retransmit attempt.



           attempts:n
           retry:n

               Sets  the number of times the resolver will send a query to its
               name servers before giving up and returning  an  error  to  the
               calling  application.  The  default  is  RES_DFLRETRY. See <re‐
               solv.h>.



           rotate

               Sets RES_ROTATE in _res.options. The name servers  are  queried
               round-robin  from  among those listed. The query load is spread
               among all listed servers, rather than having  all  clients  try
               the first listed server first every time.


           no-check-names

               Sets  RES_NOCHECKNAME in _res.options. This disables the modern
               BIND checking of incoming host names and mail names for invalid
               characters such as underscore (_), non-ASCII, or control  char‐
               acters.


           inet6

               Sets  RES_USE_INET6  in _res.options. In the Solaris BIND port,
               this has no effect on gethostbyname(3C). To retrieve  IPv6  ad‐
               dresses  or IPv4 addresses, use getaddrinfo(3C) instead of set‐
               ting inet6.




       The domain and search properties are mutually  exclusive.  If  both  of
       these properties are present, the search property takes precedence.


       For  information about how to enable a DNS client, see DNS and the Ser‐
       vice Management Facility in Working With Oracle Solaris 11.4  Directory
       and Naming Services: DNS and NIS.


       For  more  information  on how to use SMF commands to view and manually
       set the DNS client configuration properties, see the See Also section.


       Additionally automatic configuration of DNS client properties may  take
       place  under  certain conditions, (the primary system network interface
       has one DHCP address and no other addresses configured over it, and the
       DHCP server serving that DHCP address also supplies  DHCP  options  for
       DNS  configuration). Where these conditions are not met, it is possible
       to nominate a unique DHCP address to supply DHCP options for  DNS  con‐
       figuration  using  the  dhcpinfo-option-source  address  property,  see
       ipadm(8). Automated configuration of  the  DNS  client  may  result  in
       changes  to  /etc/resolv.conf(5)  which administrators find unexpected.
       Where desired an administrator may suppress this  automatic  configura‐
       tion of the DNS client by setting the config/ignore_dhcp_config parame‐
       ter  of  the svc:/network/service:default service to true, see examples
       section for details.


       Finer grained control of what dhcpv4 or dhcpv6 options the DHCP  client
       requests  or  accepts  can be obtained using ipadm properties param-re‐
       quest-list and param-ignore-list, see example section for details.

ENVIRONMENT VARIABLES
       Several environment variables can override the settings in the resolver
       configuration. However, these variables are only supported when an  ap‐
       plication  is compiled to directly call APIs from the resolver(3RESOLV)
       library. Most applications are instead compiled to use higher level in‐
       terfaces such as getaddrinfo(3C) that use the nsswitch.conf(5) configu‐
       ration to determine which sources of host name and address  information
       to use for lookups, instead of hardcoding to DNS by calling the DNS re‐
       solver directly, so these environment variables will not be effective.


       You can override the domain and search properties of the system config‐
       uration  on a per-process basis by setting the environment variable LO‐
       CALDOMAIN to a space-separated list of search domains.


       You can amend the options property of the  system  configuration  on  a
       per-process  basis by setting the environment variable RES_OPTIONS to a
       space-separated list of resolver options.


       The HOSTALIASES environment variable specifies  a  file  listing  addi‐
       tional  aliases  for  hosts, which may be used by the resolver(3RESOLV)
       library unless the application specifies the RES_NOALIASES option.

EXAMPLES
       Example 1 Listing Available Configuration Parameters



       Use the following command to list the available  configuration  parame‐
       ters for svc:/network/dns/client:


         $ svccfg -s network/dns/client describe -tv config


       Example 2 Configuring a Client



       Use  the following commands to configure a client in subdomain us.exam‐
       ple.com to use two DNS servers, to try a givenname as-is if it has  two
       or more dots, and to only make two attempts to contact each server:


         $ svccfg -s svc:/network/dns/client setprop \
             config/nameserver = net_address: \(192.168.0.1 10.0.0.1\)
         $ svccfg -s svc:/network/dns/client \
             setprop config/search = astring: \(us.example.com example.com\)
         $ svccfg -s svc:/network/dns/client \
             setprop config/options = astring: \"ndots:2 attempts:2\"
         $ svcadm refresh svc:/network/dns/client




       A few points to note while executing this example:

           o      The attempts option here is overridden by the retries option
                  in  nsswitch.conf(5)  when  standard  application interfaces
                  such as getaddrinfo(3C) and getnameinfo(3C) are used.


           o      The config/search and config/nameserver properties take mul‐
                  tiple values, not a space separated list.


           o      The config/options property takes a space separated list  of
                  options, not multiple values.


           o      refresh  is  necessary for the requested changes to take ef‐
                  fect.


       Example 3 Disabling DHCP automatic configuration of the DNS client.


         # svccfg -s network/service setprop config/ignore_dhcp_config = true
         # svcadm refresh network/service


       Example 4 Disabling recognition of IPv4 DNS  parameters  (DNSserv,DNSd‐
       main,DNSDomSearch) by DHCP client.



       This  method  allows  an administrator to decide which, if any of these
       DNS client configuration options can be automatically set as  a  result
       of   DHCP   server   supplied   options.   See   /etc/dhcp/inittab   or
       /etc/dhcp/inittab6 for dhcpv4 / dhcpv6 option  name  to  option  number
       translations.


         # ipadm set-prop -p param-ignore-list=6,15,119 dhcpv4


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       tab()  box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
       TRIBUTE VALUE _ Interface StabilityCommitted _ StandardBIND 8.3.3


SEE ALSO
       svcprop(1), sysinfo(2),  getaddrinfo(3C),  gethostbyname(3C),  gethost‐
       name(3C), getipnodebyname(3C), getnameinfo(3C), resolver(3RESOLV), nss‐
       witch.conf(5),  attributes(7),  dhcpagent(8),  domainname(8), ipadm(8),
       svcadm(8), svccfg(8)


       Managing System Services in Oracle Solaris 11.4


       Working With Oracle Solaris 11.4 Directory and Naming Services: DNS and
       NIS

Oracle Solaris 11.4               16 Sep 2025                   resolv.conf(5)
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