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Let's move on. rc.inet2 is used to run various daemons used by the TCP/IP suite. These are not necessary in order for your system to talk to the network, and are therefore relegated to a separate rc file. In most cases you should attempt to configure rc.inet1, and ensure that your system is able to send and receive packets from the network, before bothering to configure rc.inet2.

Among the daemons executed by rc.inet2 are inetd , syslogd, and routed. The version of rc.inet2 on your system may currently start a number of other servers, but we suggest commenting these out while you are debugging your network configuration.

The most important of these servers is inetd, which acts as the "operator" for other system daemons. It sits in the background and listens to certain network ports for incoming connections. When a connection is made, inetd spawns a copy of the appropriate daemon for that port. For example, when an incoming FTP connection is made, inetd forks in.ftpd, which handles the FTP connection from there. This is simpler and more efficient than running individual copies of each daemon. This way, network daemons are executed on demand.

syslogd is the system logging daemon; it accumulates log messages from various applications and stores them into logfiles based on the configuration information in /etc/syslogd.conf.

routed is a server used to maintain dynamic routing information. When your system attempts to send packets to another network, it may require additional routing table entries in order to do so. routed takes care of manipulating the routing table without the need for user intervention.

Here is a sample rc.inet2 that starts up syslogd, inetd, and routed:

#! /bin/sh

# Sample /etc/init.d/rc.inet2

# Start syslogd

if [ -f /usr/sbin/syslogd ]

then

/usr/sbin/syslogd

fi

# Start inetd

if [ -f /usr/sbin/inetd ]

then

/usr/sbin/inetd

fi

# Start routed

if [ -f /usr/sbin/routed ]

then

/usr/sbin/routed -q

fi

Among the various additional servers you may want to start in rc.inet2 is named. named is a nameserver: it is responsible for translating (local) IP addresses to names, and vice versa. If you don't have a nameserver elsewhere on the network, or if you want to provide local machine names to other machines in your domain, it may be necessary to run named. named configuration is somewhat complex and requires planning; we refer interested readers to DNS and BIND (O'Reilly).

/etc/hosts

/etc/hosts contains a list of IP addresses and the hostnames they correspond to. In general, /etc/hosts contains entries for your local machine and perhaps other "important" machines (such as your nameserver or gateway). Your local nameserver provides address-to-name mappings for other machines on the network transparently. It is in fact possible to only get your address-to-name mappings from the /etc/hosts file , without running a local nameserver at all. If you only have a few machines on your network, that may well be possible. But if you have more, then you would have to change the /etc/hosts file on each machine for each change, a task that grows quadratic in size with the number of machines and quickly becomes infeasible.

For example, if your machine is eggplant.veggie.com with the IP address 128.17.75.20, your /etc/hosts would look like this:

127.0.0.1 localhost

128.17.75.20 eggplant.veggie.com eggplant

If you're just using loopback, the only line in the /etc/hosts file should be for the address 127.0.0.1.

/etc/networks

The /etc/networks file lists the names and addresses of your own and other networks. It is used by the route command and allows you to specify a network by name instead of by address.

Every network you wish to add a route to using the route command (generally called from rc.inet1) should have an entry in /etc/networks for convenience; otherwise, you will have to specify the network's IP address instead of the name.

As an example:

default 0.0.0.0 # default route - mandatory