Using the Network Configuration Manager

The network-config-manager nmctl allows to configure and introspect the state of the network links as seen by systemd-networkd. nmctl can be used to query and configure links for Address, Routes, Gateways and also hostname, DNS, NTP or Domain. nmctl uses sd-bus, libudev APIs to interact with systemd, systemd-networkd, systemd-resolved, systemd-hostnamed, and systemd-timesyncd via dbus. nmctl uses networkd verbs to explain output. nmctl can generate configurations for required network links from YAML description. It also understands kernel command line specified in dracut network configuration format and can generate systemd-networkd configuration while the system boots and will persist between reboots.

Note: See systemd.network for more information.

nmctl is used to configure:

  • Static IPv4 and IPv6 Address, Routes, Gateway
  • DHCP type (IPv4/IPv6), DHCP4 Client Identifier, UseMTU/UseDNS/UseDomains/UseNTP/UseRoutes. LLDP, Link Local Addressing, IPv4LLRoute, LLMNR
  • DNS, Domains and NTP
  • Link MAC, MTU
  • Create netdevs, vlan, vxlan, bridge, bond, veth, macvlan/macvtap, ipvlap/ipvtap, veth, tunnels(ipip, sit, gre, sit, vti), wireguard
  • Hostname
  • Can delete and view nftables table, chains and rules.

You can use nmctl to generate network configurations from the following:

  • YAML file: nmctl can generate configurations for required network links from YAML description. Configuration written to disk under /etc/systemd/network will persist between reboots. When netmgr-yaml-generator.service is enabled it reads YAML files from /etc/network-config-manager/yaml and generates systemd-networkd configuration files.

    nmctl uses similar format as defined by different YAML format.

    nmctl can generate WPA Supplicant configuration from YAML file. When a YAML file with wifi configuration is found, it generates a configuration file found in /etc/network-config-manager/wpa_supplicant_photon_os.conf which is understood by wpa_supplicant.

  • Dracut kernel command line network configuration: nmctl understands kernel command line specified in dracut’s network configuration format and can generate systemd-networkd’s configuration while the system boots and will persist between reboots.

Network
       ip={dhcp|on|any|dhcp6|auto6}
           dhcp|on|any: get ip from dhcp server from all links. If root=dhcp, loop
           sequentially through all links (eth0, eth1, ...) and use the first with a valid
           DHCP root-path.

           auto6: IPv6 autoconfiguration

           dhcp6: IPv6 DHCP

       ip=<link>:{dhcp|on|any|dhcp6|auto6}
           dhcp|on|any|dhcp6: get ip from dhcp server on a specific link

           auto6: do IPv6 autoconfiguration

           This parameter can be specified multiple times.

       ip=<client-IP>:[ <server-id>]:<gateway-IP>:<netmask>:<client_hostname>:<link>:{none|off}
           explicit network configuration.

       ifname=<link>:<MAC>
           Assign network device name <link> (ie eth0) to the NIC with MAC <MAC>. Note
           letters in the MAC-address must be lowercase!  Note: If you use this option you must
           specify an ifname= argument for all links used in ip= or fcoe= arguments.  This
           parameter can be specified multiple times.

       nameserver=<IP>[nameserver=<IP> ...]
           specify nameserver(s) to use

      cat /proc/cmdline
       BOOT_IMAGE=/boot/vmlinuz-4.19.52-2.ph3-esx root=PARTUUID=ebf01b6d-7e9c-4345-93f4-122f44eb2726
       init=/lib/systemd/systemd rcupdate.rcu_expedited=1 rw systemd.show_status=0 quiet noreplace-smp
       cpu_init_udelay=0 net.ifnames=0 plymouth.enable=0 systemd.legacy_systemd_cgroup_controller=yes
       ip=dhcp

network-config-manager-generator.service is a oneshot type systemd service unit which runs while the system boots. It parses the kernel command line and generates networkd config in /etc/systemd/network:

systemctl enable network-config-manager-generator.service

It creates symlink /etc/systemd/system/network.target.wants/network-config-manager-generator.service → /usr/lib/systemd/system/network-config-manager-generator.service.

For more information, see:

Last modified March 24, 2021: big docs v4 cleanup (80869a1a7)