See also Remove Netplan

nmcli con show

nmcli con mod "Wired connection 1" ipv4.method manual \
  ipv4.addr 192.168.100.3/24 \
  ipv4.gateway 192.168.100.1 \
  ipv4.dns 192.168.100.1,8.8.8.8,8.8.4.4 \
  connection.id "Office LAN"

nmcli con up "Office LAN"

https://netplan.io/examples/

https://blog.ubuntu.com/2017/07/05/quick-and-easy-network-configuration-with-netplan

https://blog.ubuntu.com/2017/12/01/ubuntu-bionic-netplan

Indentation is very important!

We use netplan and networkd for network configuration.

YAML files can be renamed.

• bonds
• bridges
• vlans
• standalone network interfaces
• static addresses
• DHCP addresses

sudo netplan --debug generate
sudo netplan --debug apply

network:
  version: 2
  ethernets:
    enp0s8:
      dhcp4: no
    enp0s9:
      dhcp4: no
  bonds:
    bond0:
      interfaces: [enp0s8, enp0s9]
      addresses: [10.1.1.19/24]
      routes:
        - to: default
          via: 10.1.1.1
      nameservers:
        search: [internal.domain, domain]
        addresses: [10.1.1.20, 10.1.1.21]
      parameters:
        mode: 802.3ad
        transmit-hash-policy: layer3+4
        mii-monitor-interval: 1

sudo vi /etc/netplan/50-cloud-init.yaml

Example:

network:
  ethernets:
    eth0:
      addresses: [10.1.1.17/24]
      routes:
        - to: 0.0.0.0/0
          via: 10.0.0.1
      nameservers:
        addresses: [10.1.1.20,10.1.1.21]
    eth1:
      addresses: [10.1.9.17/24]
        mtu: 9000
version: 2

If you have trouble with netplan, try removing these files, then regenerate and reapply:

• Extra addresses
• Extra routes

rm /run/network/dynamic-interfaces
rm /run/netplan/eth0.yaml
rm /run/net-eth0.conf

Remove some unnecessary junk from your server, then configure:

apt-get purge network-manager resolvconf rdnssd
rm -f /etc/resolv.conf

sudo vim /etc/network/interfaces

auto eth0
iface eth0 inet static
        address 192.168.1.30
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.1.255
        gateway 192.168.1.1
        dns-search sonoracomm.local
        dns-nameservers 8.8.8.8 8.8.4.4

hostname short-hostname
hostnamectl set-hostname fqdn-host-name

sudo vim /etc/hosts

192.168.1.30   hostname.example.com     hostname

echo new-hostname > /etc/hostname

hostname
hostname -f

See below to configure name resolution before rebooting.

sudo reboot

CentOS 8: https://www.howtoforge.com/how-to-configure-a-static-ip-address-on-centos-8/

You can use the ncurses-based utility 'system-config-network-tui', but it installs quite a few dependencies for a minimal system. You may have to install it if it's not already installed:

yum install system-config-network-tui
yum remove NetworkManager

system-config-network-tui

or by manually editing configuration files for more control:

vi /etc/sysconfig/network

NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=shorthostname
GATEWAY=192.168.1.1

vi /etc/sysconfig/network-scripts/ifcfg-eth0

NM_CONTROLLED=no
DEVICE=eth0
BOOTPROTO=none
IPADDR=192.168.1.30
NETMASK=255.255.255.0
ONBOOT=yes

systemctl stop network.service && systemctl start network.service && systemctl enable network.service

systemctl restart NetworkManager.service

ifconfig | more

route -n

If you have problems, you may want to remove other configuration files that can confuse things. While there are legitimate reasons to have files in these folders, they will probably just complicate simple networking configurations:

rm /etc/sysconfig/networking/devices/*
rm /etc/sysconfig/networking/profiles/default/*

service network restart

If the hostname reverts back to the old hostname after a reboot:

sudo sed -i '/preserve_hostname: false/c\preserve_hostname: true' /etc/cloud/cloud.cfg && sudo hostnamectl set-hostname shorthostname

Set the hostname:

hostnamectl set-hostname <fqdn>
hostnamectl status
systemctl restart systemd-hostnamed
cat /etc/hostname


vi /etc/hosts

192.168.1.30   hostname.example.com     hostname

systemctl stop network.service && systemctl start network.service && systemctl enable network.service

hostname
hostname -f

If both hostname commands show the FQDN, try rebooting before troubleshooting further.

If you continue to have problems, you may want to remove other configuration files that can confuse things. While there are legitimate reasons to have files in these folders, they will probably just complicate simple networking configurations:

rm /etc/sysconfig/networking/devices/*
rm /etc/sysconfig/networking/profiles/default/*

service network restart

systemd-resolve --status

resolvectl status

https://www.shellhacks.com/setup-dns-resolution-resolvconf-example/

Applies to Debian and Enterprise Linux distros.

Purge the resolvconf package first!

If you have trouble saving the edited file, you may need to delete a 'leftover' symlink created by the (now removed) resolvconf package.

vi /etc/resolv.conf

nameserver 192.168.0.2
nameserver 8.8.8.8
domain example.com
search example.com local.lan

Disable systemd-resolved and use /etc/resolv.conf:

vi /etc/systemd/resolved.conf

DNSStubListener=no

systemctl stop systemd-resolved
systemctl status systemd-resolved

vim /etc/resolv.conf
reboot

sed -i -e 's/GRUB_TIMEOUT=0/GRUB_TIMEOUT=5/g' /etc/default/grub
update-grub