LPIC-1 Essential System Services and Networking Practice Question
After a reboot, a server fails to obtain an IP address on its sole ethernet interface. The administrator checks /etc/netplan/01-netcfg.yaml and finds the configuration looks correct. However, the interface shows no IP. The system uses systemd-networkd. Which command should be run next to apply the configuration and bring up the interface?
⚠ Common exam trap
Test-takers frequently assume 'systemctl restart systemd-networkd' is sufficient, but without running 'netplan apply' first, the backend configuration files are not regenerated from the YAML, so the interface remains unconfigured.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
netplan apply
The correct command is 'netplan apply' because the system uses netplan to manage network configuration, which generates backend configuration files for systemd-networkd. After editing the YAML file, 'netplan apply' parses the configuration, applies it to the running system, and triggers systemd-networkd to reconfigure the interface without requiring a full restart of the service.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
netplan apply
Why this is correct
`netplan apply` parses the YAML and hands the resulting configuration to the systemd-networkd backend, which then brings the interface up and requests a lease. Since the stem confirms systemd-networkd is the renderer and the file is already correct, this regenerates and reloads the network state without a reboot.
- ✗
ifup eth0
Why it's wrong here
ifup belongs to the ifupdown toolset and does not read Netplan YAML, so it cannot apply this configuration under systemd-networkd. It is tempting because it brings interfaces up on Debian systems using /etc/network/interfaces, which is the correct tool only there.
- ✗
systemctl restart networking
Why it's wrong here
The networking service belongs to ifupdown and is absent or inactive on a Netplan plus systemd-networkd host, so restarting it changes nothing. It is the right action on Debian systems using /etc/network/interfaces, not on this Ubuntu-style Netplan configuration.
- ✗
systemctl restart systemd-networkd
Why it's wrong here
Restarting systemd-networkd re-reads its own configuration but does not regenerate backend files from Netplan YAML, so a newly edited 01-netcfg.yaml stays unapplied. It suits picking up changes already rendered into /run/systemd/network; Netplan edits require netplan apply or netplan try instead.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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