Knowledge Base
systemd-networkd
2 min read

systemd-networkd is a system daemon that manages network configurations for Linux systems. It is part of the systemd suite and is especially well-suited for headless servers, embedded systems, containers, and systems where declarative, minimal configuration is desired.

Components of systemd-networkd

• systemd-networkd: The core daemon that applies network configurations.
• systemd-networkd-wait-online: Utility .target to block until network is up.
• networkctl: CLI tool for status and control.
• Configuration files:
• .network files for interface settings
• .netdev files for virtual devices
• .link files for hardware settings

Configuration Files

Located in:

• /etc/systemd/network/ (user configs)
• /run/systemd/network/ (runtime)
• /lib/systemd/network/ (default configs)


Set hardware-specific settings like MTU, MAC address, name policy.

Example: 10-eth0.link

ini
[Match]
MACAddress=de:ad:be:ef:00:01

[Link]
Name=lan0
MTUBytes=1500

Network Files

Configure IP settings, DHCP, DNS, routes.

Example: 10-lan0.network

ini
[Match]
Name=lan0

[Network]
Address=192.168.1.10/24
Gateway=192.168.1.1
DNS=1.1.1.1

[DHCP]
UseDNS=false

NetDev Files

Create virtual devices like bridges, VLANs, bonds, tunnels.

Example: 10-br0.netdev

ini
[NetDev]
Name=br0
Kind=bridge

Configuration Examples

Static IP Address

ini
[Match]
Name=eth0

[Network]
Address=10.0.0.5/24
Gateway=10.0.0.1
DNS=1.1.1.1

DHCP Client

ini
[Match]
Name=enp3s0

[Network]
DHCP=yes

Bridge Interface

Create the bridge:

ini
# 10-br0.netdev
[NetDev]
Name=br0
Kind=bridge

Attach interfaces:

ini
# 10-eth0.network
[Match]
Name=eth0

[Network]
Bridge=br0

Assign IP to bridge:

ini
# 10-br0.network
[Match]
Name=br0

[Network]
Address=192.168.1.100/24
Gateway=192.168.1.1
DNS=1.1.1.1

VLAN Interface

ini
# 10-vlan10.netdev
[NetDev]
Name=vlan10
Kind=vlan

[VLAN]
Id=10

# 10-vlan10.network
[Match]
Name=vlan10

[Network]
Address=192.168.10.1/24

Bonding

ini
# 10-bond0.netdev
[NetDev]
Name=bond0
Kind=bond

[Bond]
Mode=active-backup

# 10-bond0.network
[Match]
Name=bond0

[Network]
DHCP=yes

# 10-eth0.network
[Match]
Name=eth0

[Network]
Bond=bond0

# 10-eth1.network
[Match]
Name=eth1

[Network]
Bond=bond0

Usage

bash
# Start and enable
sudo systemctl enable --now systemd-networkd

# Restart
sudo systemctl restart systemd-networkd

# Reload configs without restart
sudo networkctl reload

# View status
networkctl status

# Show all interfaces and their states
networkctl list

# Detailed status of one interface
networkctl status eth0

# Show address assignments
ip addr

# Show routes
ip route

# Journal logs
journalctl -u systemd-networkd

Integration with systemd-resolved

To handle DNS:

ini
[Network]
DNS=1.1.1.1
Domains=~example.com

Then enable:

bash
sudo systemctl enable --now systemd-resolved

Integration with systemd-timesyncd

To enable automatic NTP time sync:

bash
sudo systemctl enable --now systemd-timesyncd

In network config:

ini
[Network]
NTP=ntp.example.com