This section only applies if a network card is to be configured.
Starting with version 209, systemd ships a network configuration
daemon called systemd-networkd which can be
used for basic network configuration. Additionally, since version
213, DNS name resolution can be handled by systemd-resolved in place of a
static /etc/resolv.conf
file. Both
services are enabled by default.
If you will not use systemd-networkd for network configuration (for example, when the system is not connected to network, or you want to use another utility like NetworkManager for network configuration), disable a service to prevent an error message during boot:
systemctl disable systemd-networkd-wait-online
Configuration files for systemd-networkd (and
systemd-resolved) can
be placed in /usr/lib/systemd/network
or /etc/systemd/network
. Files in
/etc/systemd/network
have a higher
priority than the ones in /usr/lib/systemd/network
. There are three types
of configuration files: .link
,
.netdev
and .network
files. For detailed descriptions and
example contents of these configuration files, consult the
systemd.link(5),
systemd.netdev(5),
and systemd.network(5)
manual pages.
Udev normally assigns network card interface names based on physical system characteristics such as enp2s1. If you are not sure what your interface name is, you can always run ip link after you have booted your system.
The interface names depend on the implementation and configuration of the udev daemon running on the system. The udev daemon for LFS (systemd-udevd, installed in Section 8.76, “Systemd-256.4”) will not run unless the LFS system is booted. So it's unreliable to determine the interface names being used in LFS system by running those commands on the host distro, even though you are in the chroot environment.
For most systems, there is only one network interface for each type of connection. For example, the classic interface name for a wired connection is eth0. A wireless connection will usually have the name wifi0 or wlan0.
If you prefer to use the classic or customized network interface names, there are three alternative ways to do that:
Mask udev's .link
file for
the default policy:
ln -s /dev/null /etc/systemd/network/99-default.link
Create a manual naming scheme, for example by naming the
interfaces something like internet0
, dmz0
, or lan0
. To do that, create .link
files in /etc/systemd/network/ that
select an explicit name or a better naming scheme for your
network interfaces. For example:
cat > /etc/systemd/network/10-ether0.link << "EOF"
[Match]
# Change the MAC address as appropriate for your network device
MACAddress=12:34:45:78:90:AB
[Link]
Name=ether0
EOF
See systemd.link(5) for more information.
In /boot/grub/grub.cfg, pass the option net.ifnames=0
on the kernel command line.
The command below creates a basic configuration file for a Static IP setup (using both systemd-networkd and systemd-resolved):
cat > /etc/systemd/network/10-eth-static.network << "EOF"
[Match]
Name=<network-device-name>
[Network]
Address=192.168.0.2/24
Gateway=192.168.0.1
DNS=192.168.0.1
Domains=<Your Domain Name>
EOF
Multiple DNS entries can be added if you have more than one DNS
server. Do not include DNS or Domains entries if you intend to
use a static /etc/resolv.conf
file.
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
.
If using methods incompatible with systemd-resolved to
configure your network interfaces (ex: ppp, etc.), or if using
any type of local resolver (ex: bind, dnsmasq, unbound, etc.),
or any other software that generates an /etc/resolv.conf
(ex: a resolvconf program other than
the one provided by systemd), the systemd-resolved service
should not be used.
To disable systemd-resolved, issue the following command:
systemctl disable systemd-resolved
When using systemd-resolved for DNS
configuration, it creates the file /run/systemd/resolve/stub-resolv.conf
. And, if
/etc/resolv.conf
does not exist, it
will be created by systemd-resolved as a symlink
to /run/systemd/resolve/stub-resolv.conf
. So it's
unnecessary to create a /etc/resolv.conf
manually.
If a static /etc/resolv.conf
is
desired, create it by running the following command:
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 server
most appropriate for your 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. Another option is to use the Google Public DNS service
using the IP addresses below as nameservers.
The Google Public IPv4 DNS addresses are 8.8.8.8
and 8.8.4.4
for IPv4, and 2001:4860:4860::8888
and
2001:4860:4860::8844
for IPv6.
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 a fully-qualified domain name (FQDN), and possible
aliases for use in the /etc/hosts
file. If using static IP addresses, you'll also need to decide on
an IP address. The syntax for a hosts file entry 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.
If the computer is to be visible to the Internet, a valid FQDN can be the domain name itself, or a string resulted by concatenating a prefix (often the hostname) and the domain name with a “.” character. And, you need to contact the domain provider to resolve the FQDN to your public IP address.
Even if the computer is not visible to the Internet, a FQDN is
still needed for certain programs, such as MTAs, to operate
properly. A special FQDN, localhost.localdomain
, can be used for this
purpose.
Create the /etc/hosts
file using the
following command:
cat > /etc/hosts << "EOF"
# Begin /etc/hosts
<192.168.0.2>
<FQDN>
[alias1] [alias2] ...
::1 ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
# End /etc/hosts
EOF
The <192.168.0.2>
and <FQDN>
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, and the <192.168.0.2>
line can be
omitted if you are using a connection configured with DHCP or IPv6
Autoconfiguration, or using localhost.localdomain
as the FQDN.
The /etc/hostname
does not contain
entries for localhost
, localhost.localdomain
, or the hostname (without a
domain) because they are handled by the myhostname
NSS module, read the man page
nss-myhostname(8)
for details.
The ::1 entry is the IPv6 counterpart of 127.0.0.1 and represents the IPv6 loopback interface.