1RESOLVER(5) 386BSD Programmer's Manual RESOLVER(5) 2 3NNAAMMEE 4 rreessoollvveerr - resolver configuration file 5 6SSYYNNOOPPSSIISS 7 rreessoollvv..ccoonnff 8 9DDEESSCCRRIIPPTTIIOONN 10 The resolver(3) is a set of routines in the C library which provide ac- 11 cess to the Internet Domain Name System. The resolver configuration file 12 contains information that is read by the resolver routines the first time 13 they are invoked by a process. The file is designed to be human readable 14 and contains a list of keywords with values that provide various types of 15 resolver information. 16 17 On a normally configured system this file should not be necessary. The 18 only name server to be queried will be on the local machine, the domain 19 name is determined from the host name, and the domain search path is con- 20 structed from the domain name. 21 22 The different configuration options are: 23 24 nnaammeesseerrvveerr Internet address (in dot notation) of a name server that the 25 resolver should query. Up to MAXNS (currently 3) name 26 servers may be listed, one per keyword. If there are multi- 27 ple servers, the resolver library queries them in the order 28 listed. If no nnaammeesseerrvveerr entries are present, the default is 29 to use the name server on the local machine. (The algorithm 30 used is to try a name server, and if the query times out, try 31 the next, until out of name servers, then repeat trying all 32 the name servers until a maximum number of retries are made). 33 34 ddoommaaiinn Local domain name. Most queries for names within this domain 35 can use short names relative to the local domain. If no 36 ddoommaaiinn entry is present, the domain is determined from the 37 local host name returned by gethostname(2); the domain part 38 is taken to be everything after the first `.'. Finally, if 39 the host name does not contain a domain part, the root domain 40 is assumed. 41 42 sseeaarrcchh Search list for host-name lookup. The search list is normal- 43 ly determined from the local domain name; by default, it be- 44 gins with the local domain name, then successive parent do- 45 mains that have at least two components in their names. This 46 may be changed by listing the desired domain search path fol- 47 lowing the sseeaarrcchh keyword with spaces or tabs separating the 48 names. Most resolver queries will be attempted using each 49 component of the search path in turn until a match is found. 50 Note that this process may be slow and will generate a lot of 51 network traffic if the servers for the listed domains are not 52 local, and that queries will time out if no server is avail- 53 able for one of the domains. 54 55 The search list is currently limited to six domains with a 56 total of 256 characters. 57 58 The ddoommaaiinn and sseeaarrcchh keywords are mutually exclusive. If more than one 59 instance of these keywords is present, the last instance will override. 60 61 The keyword and value must appear on a single line, and the keyword (e.g. 62 nnaammeesseerrvveerr) must start the line. The value follows the keyword, separat- 63 ed by white space. 64 65FFIILLEESS 66 67 /etc/resolv.conf The file rreessoollvv..ccoonnff resides in /_e_t_c. 68 69SSEEEE AALLSSOO 70 gethostbyname(3), resolver(3), hostname(7), named(8) 71 72 _N_a_m_e _S_e_r_v_e_r _O_p_e_r_a_t_i_o_n_s _G_u_i_d_e _f_o_r _B_I_N_D. 73 74HHIISSTTOORRYY 75 The rreessoollvv..ccoonnff file format appeared in 4.3BSD. 76 774th Berkeley Distribution May 10, 1991 3 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133