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13. Setting up basic networking

13.1 Installing Netkit-base

13.2 Installing Net-tools

Creating the /etc/init.d/localnet bootscript 

#!/bin/sh
# Begin /etc/init.d/localnet
 
check_status()
{
  if [ $? = 0 ]
  then
    echo "OK"
  else
    echo "FAILED"
  fi
}
 
echo -n "Setting up loopback device..."
/sbin/ifconfig lo 127.0.0.1
check_status
 
echo -n "Setting up hostname..."
/bin/hostname --file /etc/hostname
check_status
 
# End /etc/init.d/localnet

Setting up permissions and symlink

Creating the /etc/hostname file

Create a new file /etc/hostname and put the hostname in it. This is not the FQDN (Fully Qualified Domain Name). This is the name you wish to call your computer in a network.

Creating the /etc/hosts file

If you want to configure a network card, you have to decide on the IP-address, FQDN and possible aliases for use in the /etc/hosts file. An example is: 

<myip> myhost.mydomain.org somealiases

Make sure the IP-address is in the private network IP-address range. Below a quoted paragraph from O'Reilly's book "Linux Network Administrator's Guide"

--- Begin quote ---

If your network is not connected to the Internet and won't be in the near future, you are free to choose any legal network address. Just make sure no packets from your internal network escape to the real Internet. To make sure no harm is done, even when packets did escape, you should use one of the network numbers reserved for private use. The Internet Assigned Numbers Authority (IANA) has set aside several network numbers from classes A, B and C that you can use without registering. These addresses are only valid within your private network and are not routed between Internet sites.

The numbers are: 

Class Networks
A     10.0.0.0
B     172.16.0.0 through 172.31.0.0
C     192.168.0.0 through 192.168.255.0

--- End quote ---

A valid IP address could be 192.168.1.1. A valid FQDN for this IP could be me.lfs.org

If you're not going to use a network card, you still need to come up with a FQDN. This is necessary for programs like Sendmail to operate correctly (in fact; Sendmail won't run when it can't determine the FQDN).

Here's the /etc/hosts file if you don't configure a network card: 

# Begin /etc/hosts (no network card version)
127.0.0.1 me.lfs.org <contents of /etc/hostname> localhost
# End /etc/hosts (no network card version)

Here's the /etc/hosts file if you do configure a network card: 

# Begin /etc/hosts (network card version)
127.0.0.1 localhost
192.168.1.1 me.lfs.org <contents of /etc/hostname>
# End /etc/hosts (network card version)

Of course, change the 192.168.1.1 and me.lfs.org to your own liking (or requirements if you are assigned an IP-address by a network/system administrator and you plan on connecting this machine to that network).

Creating the /etc/init.d/ethnet file

This sub section only applies if you are going to configure a network card. If not, skip this sub section and read on.

Create a new file /etc/init.d/ethnet containing the following: 

#!/bin/sh
# Begin /etc/init.d/ethnet
 
check_status()
{
  if [ $? = 0 ]
  then
    echo "OK"
  else
    echo "FAILED"
  fi
}
 
/sbin/ifconfig eth0 <ipaddress>
check_status
 
# End /etc/init.d/ethnet

Setting up permissions and symlink for /etc/init.d/ethnet

Testing the network setup 

ping <your FQDN>
ping <what you choose for hostname>
ping localhost
ping 127.0.0.1
ping 192.168.1.1 (only when you configured your network card)

All these five ping command's should work without failures. If so, the basic network is working.

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