The resolver is the part of the system that turns IP addresses
into hostnames and vice versa. It can be configured to look for
maps that describe IP to hostname mappings in one of two places.
The first is a file called /etc/hosts (man 5 hosts).
The second is the Internet Domain Name Service (DNS), a distributed
data base, the discussion of which is beyond the scope of this document.
This section describes briefly how to configure your resolver.
The resolver is a set of system calls that do the name mappings, but
you have to tell them where to find their information. You do
this by first editing the file /etc/host.conf. Do
not call this file /etc/hosts.conf (note the extra
``s'') as the results can be confusing.
This file should contain the following two lines (in this order):
hosts
bind
which instructs the resolver to first look in the file
/etc/hosts, and then to consult the DNS if the
name was not found.
This file should contain the IP addresses and names of machines on your
network. At a bare minimum it should contain entries for the machine
which will be running ppp. Assuming that your machine is called
foo.bar.com with the IP address 10.0.0.1, /etc/hosts should
contain:
127.0.0.1 localhost
10.0.0.1 foo.bar.com foo
The first line defines the alias ``localhost'' as a synonym for the current machine. Regardless of your own IP address, the IP address for this line should always be 127.0.0.1. The second line maps the name ``foo.bar.com'' (and the shorthand ``foo'') to the IP address 10.0.0.1.
If your provider allocates you a static IP address and name, then use these in place of the 10.0.0.1 entry.
/etc/resolv.conf tells the resolver how to behave. If you are
running your own DNS, you may leave this file empty. Normally, you will
need to enter the following line(s):
nameserver x.x.x.x
nameserver y.y.y.y
domain bar.com
The x.x.x.x and y.y.y.y addresses are those given
to you by your ISP. Add as many ``nameserver'' lines as your ISP
provides. The ``domain'' line defaults to your hostname's domain, and
is probably unnecessary. Refer to the resolv.conf manual page for details
of other possible entries in this file.
If you're running ppp version 2 or greater, the ``enable dns'' command
will tell ppp to request that your ISP confirms the nameserver values.
If your ISP supplies different addresses (or if there are no nameserver
lines in /etc/resolv.conf), ppp will rewrite the file with the
ISP-supplied values.