Specifies the ordering of certain name resolution services.
The /etc/netsvc.conf file is used to specify the ordering of name resolution for the sendmail command, gethostbyname subroutine, gethostaddr subroutine, and gethostent subroutine and alias resolution for the sendmail command.
Several mechanisms for resolving host names and aliases are available. The gethostbyname, gethostbyaddr, and gethostent subroutines use these mechanisms for resolving names. A default order exists in which the resolver subroutines try the mechanisms for resolving host names and Internet Protocol (IP) addresses.
You can override the default order and the order given in the /etc/irs.conf file by creating the /etc/netsvc.conf configuration file and specifying the desired ordering. To specify this host ordering, create an entry in the following format:
hosts = value [, value]
Use one or more of the following values for the hosts
|auth||Designates the specified server as authoritative. A
resolver does not continue searching for host names further than an
authoritative server. For example, when two services are given as
values for the host keyword and the first service is made
authoritative, and if the resolver cannot find the host name in the
authoritative service, then the resolver terminates its search.
However, the auth option has no effect if the resolver is unable to
contact the authoritative server; in this case, the resolver continues to
search the next service given in the same entry.
Indicate that the specified service is authoritative by following it by an = and then auth.
Note: The auth option is only valid when used in conjunction with a service value for the host keyword.
|bind||Uses BIND/DNS services for resolving names|
|local||Searches the local /etc/hosts file for resolving names|
|nis||Uses NIS services for resolving names. NIS must be running if you specify this option|
|ldap||Uses LDAP services for resolving names|
|bind4||Uses BIND/DNS services for resolving only IPv4 addresses|
|bind6||Uses BIND/DNS services for resolving only IPv6 addresses|
|local4||Searches the local /etc/hosts file for resolving only IPv4 addresses|
|local6||Searches the local /etc/hosts file for resolving only IPv6 addresses|
|nis4||Uses NIS services for resolving only IPv4 addresses|
|nis6||Uses NIS services for resolving only IPv6 addresses|
|ldap4||Uses LDAP services for resolving only IPv4 addresses|
|ldap6||Uses LDAP services for resolving only IPv6 addresses|
The environment variable NSORDER overrides the host settings in the /etc/netsvc.conf file, which in turn overrides the host settings in the /etc/irs.conf file.
The sendmail command searches the local /etc/aliases file, or uses NIS if specified for resolving aliases. You can override the default by specifying how to resolve aliases in the /etc/netsvc.conf file. To specify alias ordering to the sendmail command, enter the following:
alias = value [, value]
Use one or more of the following values for the alias
|files||Searches the local /etc/aliases file for the alias|
|nis||Uses NIS services for resolving alias|
The order is specified on one line with values separated by commas. White spaces are permitted around the commas and the equal sign. The values specified and their ordering are dependent on the network configuration.
hosts = local
hosts = local , nis
hosts = ldap = auth , bind
In this example, if the resolver cannot contact the LDAP server, then it searches the BIND service.
aliases = nis
|/etc/netsvc.conf||Specifies the path to the file.|
The aliases file for mail, irs.conf file, hosts file format for TCP/IP.
The sendmail command.
The gethostbyname subroutine, gethostbyaddr subroutine, and gethostent subroutine.
TCP/IP Name Resolution in AIX 5L Version 5.1 System Management Guide: Communications and Networks