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Using image mode for RHEL to build, deploy, and manage operating systems
16.3. Network configuration

16.3. Network configuration

The default images include the NetworkManager dynamic network control and configuration system, and bootc attempts to connect by using DHCP on every interface with a cable plugged in. You can apply a temporary network configuration, by setting up the /run/NetworkManager/conf.d directory.

However, if you need to use static addressing or more complex networking such as VLANs, bonds, bridges, teams, among others, you can use different ways. Regardless of the way you choose to configure networking, it results as a configuration for NetworkManager, which takes the form of NetworkManager keyfiles.

Host Network Configuration options

Complex networking configuration often also requires per-machine state. You can generate machine-specific container images that have, for example, static IP addressing included. You can also include code to generate network configuration from inside the image by inspecting the MAC address of the host.

Network configuration options available

The following are the available options for configuring static IP, and how the configuration should be done:

By using a Containerfile: Create a container image with static IP or include code to generate network configuration from inside the image based on MAC address.
- Use the configuration specified in Device List Format to match the MAC address or other addresses.
- To configure a network, you can use the nmcli connection add similarly to what you do to a booted system. However, during build time, you must use the command combined with an explicit --offline argument. See Configuring an Ethernet connection by using nmcli for more details.
- Ensure to add the following command before the nmcli command in the ContainerFile:
  RUN nmcli --offline connection add
By using Anaconda: You can use an Anaconda Kickstart to configure networking, including Wi-Fi, for bare-metal installations. The configuration is stored by default in the /etc/NetworkManager/system-connections/ file, and is inherently per-machine state.
By using kernel arguments: Add kernel parameters on first boot to define networking configuration. On the first boot of a machine, enter kernel arguments that define networking configuration. The kernel arguments are mostly defined in the dracut.cmdline man page. You can apply these kernel arguments on first boot by using different methods. When using bootc install, you can also set per-machine kernel arguments by using --karg.
By using NetworkManager key files: nmcli or nm-initrd-generator

Generating a NetworkManager keyfiles by using nmcli

The nmcli NetworkManager command line tool provides an offline mode that does not communicate with the NetworkManager daemon and just writes the keyfile content to standard output.

Run the nmcli tool for each connection profile you want to create:

$ nmcli --offline connection add \
        type ethernet ifname enp1s0 \
        ipv4.method manual ipv4.addresses 192.0.0.1/24 \
        ipv6.method disabled

[connection]
id=ethernet-enp1s0
uuid=ff242096-f803-425f-9a77-4c3ec92686bd
type=ethernet
interface-name=enp1s0

[ethernet]

[ipv4]
address1=192.0.0.1/24
method=manual

[ipv6]
addr-gen-mode=default
method=disabled
[proxy]

See the settings man page for a list of the properties that can be specified by using nmcli. Bash autocompletion is available.

Generating NetworkManager Keyfiles by using nm-initrd-generator

NetworkManager contains the nm-initrd-generator tool, that can generate keyfiles from dracut kernel argument syntax. You can use the tool to either convert from kernel arguments to keyfiles or to just quickly generate some keyfiles giving a small amount of input and then modify some more detailed settings.

Generate keyfiles for a bond by using nm-initrd-generator:

$ podman run --rm -ti quay.io/<namespace>/<image>:<tag> /usr/libexec/nm-initrd-generator -s -- "ip=bond0:dhcp" "bond=bond0:ens2,ens3:mode=active-backup,miimon=100" "nameserver=8.8.8.8"

* Connection 'bond0' *

[connection]
id=bond0
uuid=643c17b5-b364-4137-b273-33f450a45476
type=bond
interface-name=bond0
multi-connect=1
permissions=

[ethernet]
mac-address-blacklist=

[bond]
miimon=100
mode=active-backup

[ipv4]
dns=8.8.8.8;
dns-search=
may-fail=false
method=auto

[ipv6]
addr-gen-mode=eui64
dns-search=
method=auto

[proxy]

* Connection 'ens3' *

[connection]
id=ens3
uuid=b42cc917-fd87-47df-9ac2-34622ecddd8c
type=ethernet
interface-name=ens3
master=643c17b5-b364-4137-b273-33f450a45476
multi-connect=1
permissions=
slave-type=bond

[ethernet]
mac-address-blacklist=

* Connection 'ens2' *

[connection]
id=ens2
uuid=e111bb4e-3ee3-4612-afc2-1d2dfff97671
type=ethernet
interface-name=ens2
master=643c17b5-b364-4137-b273-33f450a45476
multi-connect=1
permissions=
slave-type=bond

[ethernet]
mac-address-blacklist=

The command generates three keyfiles for each interface: bond0, ens3, and ens2. You can use the generated output, add more settings or modify existing settings, and then commit the files into a container image.

Configuring a Static IP

You can use the following dracut kernel arguments:
Template:

ip=${ip}::${gateway}:${netmask}:${hostname}:${interface}:none:${nameserver}

Example:

ip=10.10.10.10::10.10.10.1:255.255.255.0:myhostname:ens2:none:8.8.8.8

Writing configuration embedded in container images

Store the NetworkManager configuration embedded in container images in /usr/lib/NetworkManager/system-connections/ because this form is part of the immutable image state. You can also write configuration to /etc/NetworkManager/system-connections/ as part of the container image. The default OSTree 3-way merge, that is, using the old default configuration, the active /etc system, and the new default configuration, applies with any machine-specific configuration.

The keyfiles must have the 600 root-only access permissions, otherwise NetworkManager ignores them.

Disabling automatic configuration of Ethernet devices

By default, NetworkManager attempts to autoconfigure by using the DHCP or SLAAC addresses on every interface with a cable plugged in. In some network environments this might not be desirable. For that, it is possible to change the NetworkManager behavior by adding a configuration file, such as /usr/lib/NetworkManager/conf.d/noauto.conf.

Disable the NetworkManager autoconfiguration of Ethernet devices

[main]
# Do not do automatic (DHCP or SLAAC) configuration on ethernet devices
# with no other matching connections.
no-auto-default=*

16.3. Network configuration

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