This section only applies if a network card is to be configured.
Which interfaces are brought up and down by the network script
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” is
required to be a Network Card Interface name (e.g. eth0). 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.
Udev may assign random Network Card Interface names for some
network cards such as enp2s1. If you are not sure what your
Network Card Interface name is, you can always run ip l after you have booted your
system. Again, it is important that
ifconfig.xyz is named after correct Network
Card Interface name (e.g.
ifconfig.eth0) or Systemd will fail to bring up
your network interface.
The following command creates a sample file for the eth0 device with a static IP address:
cd /etc/sysconfig/ cat > ifconfig.eth0 << "EOF"
IFACE=eth0 SERVICE=ipv4-static IP=192.168.1.1 GATEWAY=192.168.1.2 PREFIX=24 BROADCAST=192.168.1.255EOF
The values of these variables must be changed in every file to match the proper setup.
IFACE variable defines the interface
name, for example, eth0. It is required for all network device
SERVICE variable defines the method
used for obtaining the IP address. The LFS-Network-Scripts package
has a modular IP assignment format, and creating additional files
allows other IP assignment methods. This is commonly used for
Dynamic Host Configuration Protocol (DHCP), which is addressed in
the BLFS book.
GATEWAY variable should contain the
default gateway IP address, if one is present. If not, then comment
out the variable entirely.
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.
Enabling of the Network Interface Card configuration is done per interface. To enable Network Interface Card configuration at boot, run:
systemctl enable ifupdown@eth0
To disable previously enabled Network Interface Card configuration at boot, run:
systemctl disable ifupdown@eth0
To manually start the Network Interface Card configuration, run:
systemctl start ifupdown@eth0
Replace eth0 with the correct Network Interface Card name as described on the beginning of this page.
If the system is going to be connected to the Internet, it will
need some means of 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
cat > /etc/resolv.conf << "EOF"
# Begin /etc/resolv.conf domainEOF
<Your Domain Name>nameserver
<IP address of your primary nameserver>nameserver
<IP address of your secondary nameserver># End /etc/resolv.conf
domain statement can be omitted or
replaced with a
search statement. See
the man page for resolv.conf for more details.
<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 126.96.36.199 and 188.8.131.52.