LPIC-1 System Architecture Practice Question
A Linux server uses a custom udev rule to assign a persistent name to a USB-to-serial adapter. After a kernel update, the adapter is no longer recognized by its custom name, and the administrator finds that the rule file is still present. Which command should be used to reload the udev rules and trigger them for existing devices without rebooting?
⚠ Common exam trap
The trap here is assuming that restarting the udev daemon or monitoring events is enough, overlooking that existing devices need an explicit trigger to be re-evaluated.
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
✓
udevadm control --reload-rules && udevadm trigger
To apply modified udev rules to devices that are already connected, the rules must be reloaded into the udev daemon and then existing devices must be re-triggered. The command udevadm control --reload-rules performs the reload, and udevadm trigger replays events for all devices. Together they activate the new rule without requiring a reboot or physical reconnection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
udevadm info --query=all --name=/dev/ttyUSB0
Why it's wrong here
udevadm info queries the udev database for a device and displays its properties, but it does not reload rules or apply changes. It is a diagnostic command used to inspect attributes and current naming, not to activate new rules. Running it would not resolve the missing custom name.
- ✗
systemctl restart systemd-udevd
Why it's wrong here
Restarting systemd-udevd stops and starts the udev daemon, which reloads rules, but it does not replay uevents for devices already present. Existing devices would not be re-processed, so the custom name would not be applied until the device is reconnected or the system reboots. The trigger step is missing.
- ✗
udevadm monitor --kernel --property
Why it's wrong here
udevadm monitor listens for kernel uevents and udev events, printing them for debugging. It does not reload rules or trigger devices. While useful to observe whether events are generated, it is a passive monitoring tool and will not cause the custom rule to be applied to the already-connected adapter.
- ✓
udevadm control --reload-rules && udevadm trigger
Why this is correct
udevadm control --reload-rules reloads the rules from /etc/udev/rules.d and /lib/udev/rules.d into the running udev daemon. udevadm trigger then replays kernel uevents for existing devices, causing the new rules to be applied. This combination applies rule changes immediately without a reboot, which is essential after modifying udev rules.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official LPI exam blueprint
This LPIC-1 practice question is part of Courseiva's free LPI certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LPIC-1 exam.