# Customizing the /etc/hosts File

If a network card is to be configured, decide on the IP address, FQDN, and possible aliases for use in the `/etc/hosts` file. The syntax is:

    <IP address> myhost.example.org aliases

Unless the computer is to be visible to the Internet (i.e., there is a registered domain and a valid block of assigned IP addresses—most users do not have this), make sure that the IP address is in the private network IP address range. Valid ranges are:

      Class Networks
      A     10.0.0.0
      B     172.16.0.0 through 172.31.0.255
      C     192.168.0.0 through 192.168.255.255

A valid IP address could be 192.168.1.1. A valid FQDN for this IP could be www.linuxfromscratch.org (not recommended because this is a valid registered domain address and could cause domain name server issues).

Even if not using a network card, an FQDN is still required. This is necessary for certain programs to operate correctly.

Create the `/etc/hosts` file by running:

    cat > /etc/hosts << "EOF"
    # Begin /etc/hosts (network card version)

    127.0.0.1 localhost
    [192.168.1.1] [<HOSTNAME>.example.org] [HOSTNAME]

    # End /etc/hosts (network card version)
    EOF

The `[192.168.1.1]` and `[<HOSTNAME>.example.org]` values need to be changed for specific users or requirements (if assigned an IP address by a network/system administrator and the machine will be connected to an existing network).

If a network card is not going to be configured, create the `/etc/hosts` file by running:

    cat > /etc/hosts << "EOF"
    # Begin /etc/hosts (no network card version)

    127.0.0.1 [<HOSTNAME>.example.org] [HOSTNAME] localhost

    # End /etc/hosts (no network card version)
    EOF