Which interfaces are brought up and down by the network script
usually depends on the files in /etc/sysconfig/
. This directory should contain a
file for each interface to be configured, such as ifconfig.xyz
, where “xyz” should
describe the network card. The interface name (e.g. eth0) is
usually appropriate. Inside this file are attributes to this
interface, such as its IP address(es), subnet masks, and so forth.
It is necessary that the stem of the filename be ifconfig.
If the procedure in the previous section was not used, udev will assign network card interface names based on system physical characteristics such as enp2s1. If you are not sure what your interface name is, you can always run ip link or ls /sys/class/net after you have booted your system.
The following command creates a sample file for the eth0 device with a static IP address:
cd /etc/sysconfig/ cat > ifconfig.eth0
<< "EOF"ONBOOT=
EOFyes
IFACE=eth0
SERVICE=ipv4-static
IP=192.168.1.2
GATEWAY=192.168.1.1
PREFIX=24
BROADCAST=192.168.1.255
The values in italics must be changed in every file to match the proper setup.
If the ONBOOT
variable is set to
“yes” the System V network script will
bring up the Network Interface Card (NIC) during the system boot
process. If set to anything but “yes” the NIC
will be ignored by the network script and not be automatically
brought up. The interface can be manually started or stopped with
the ifup and
ifdown commands.
The IFACE
variable defines the interface
name, for example, eth0. It is required for all network device
configuration files. The filename extension must match this value.
The SERVICE
variable defines the method
used for obtaining the IP address. The LFS-Bootscripts package has
a modular IP assignment format, and creating additional files in
the /lib/services/
directory allows
other IP assignment methods. This is commonly used for Dynamic Host
Configuration Protocol (DHCP), which is addressed in the BLFS book.
The GATEWAY
variable should contain the
default gateway IP address, if one is present. If not, then comment
out the variable entirely.
The PREFIX
variable contains the number
of bits used in the subnet. Each octet in an IP address is 8 bits.
If the subnet's netmask is 255.255.255.0, then it is using the
first three octets (24 bits) to specify the network number. If the
netmask is 255.255.255.240, it would be using the first 28 bits.
Prefixes longer than 24 bits are commonly used by DSL and
cable-based Internet Service Providers (ISPs). In this example
(PREFIX=24), the netmask is 255.255.255.0. Adjust the PREFIX
variable according to your specific subnet.
If omitted, the PREFIX defaults to 24.
For more information see the ifup man page.
The system will need some means of obtaining Domain Name Service
(DNS) name resolution to resolve Internet domain names to IP
addresses, and vice versa. This is best achieved by placing the IP
address of the DNS server, available from the ISP or network
administrator, into /etc/resolv.conf
.
Create the file by running the following:
cat > /etc/resolv.conf << "EOF"
# Begin /etc/resolv.conf
domain <Your Domain Name>
nameserver <IP address of your primary nameserver>
nameserver <IP address of your secondary nameserver>
# End /etc/resolv.conf
EOF
The domain
statement can be omitted or
replaced with a search
statement. See
the man page for resolv.conf for more details.
Replace <IP address of the
nameserver>
with the IP address of the DNS most
appropriate for the setup. There will often be more than one entry
(requirements demand secondary servers for fallback capability). If
you only need or want one DNS server, remove the second
nameserver line from the
file. The IP address may also be a router on the local network.
The Google Public IPv4 DNS addresses are 8.8.8.8 and 8.8.4.4.
During the boot process, the file /etc/hostname
is used for establishing the
system's hostname.
Create the /etc/hostname
file and
enter a hostname by running:
echo "<lfs>
" > /etc/hostname
<lfs>
needs to be
replaced with the name given to the computer. Do not enter the
Fully Qualified Domain Name (FQDN) here. That information is put in
the /etc/hosts
file.
Decide on the IP address, fully-qualified domain name (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:
Private Network Address Range Normal Prefix
10.0.0.1 - 10.255.255.254 8
172.x.0.1 - 172.x.255.254 16
192.168.y.1 - 192.168.y.254 24
x can be any number in the range 16-31. y can be any number in the range 0-255.
A valid private IP address could be 192.168.1.1. A valid FQDN for this IP could be lfs.example.org.
Even if not using a network card, a valid 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
127.0.0.1 localhost.localdomain localhost
127.0.1.1 <FQDN>
<HOSTNAME>
<192.168.1.1>
<FQDN>
<HOSTNAME>
[alias1] [alias2 ...]
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
# End /etc/hosts
EOF
The <192.168.1.1>
,
<FQDN>
, and
<HOSTNAME>
values
need to be changed for specific uses or requirements (if assigned
an IP address by a network/system administrator and the machine
will be connected to an existing network). The optional alias
name(s) can be omitted.