Quick Answer
The answer is the `User=` directive. This directive, placed in the `[Service]` section of a systemd unit file, tells systemd to drop root privileges and execute the service process under the specified non-root user account, such as `User=myuser`. This is the standard and correct mechanism for running a systemd service as a non-root user, directly implementing the principle of least privilege by limiting the process’s access rights and reducing the attack surface. On the LFCS exam, this concept often appears in a scenario where an administrator must harden a service; the common trap is confusing `User=` with `Group=` or forgetting that `User=` alone handles both the UID and primary GID. A reliable memory tip is to think "User first, Group second"—you set the user, and systemd automatically assigns that user’s primary group, so you only need `Group=` if you want a different supplementary group.
This LFCS practice question tests your understanding of service configuration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator needs to configure a service to run as a non-root user for security reasons. Which systemd unit file directive accomplishes this?
AmbientCapabilities=CAP_NET_BIND_SERVICE
Why wrong: This grants capabilities, not user identity.
DynamicUser=yes
Why wrong: DynamicUser= creates a transient user, but the actual user is not 'myuser'.
User=myuser
User= specifies the username or UID to run the service.
Group=myuser
Why wrong: Group= sets the group, but the user must also be specified.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
User=myuser
Option C is correct because the `User=` directive in a systemd unit file specifies the user (by name or UID) under which the service process runs. By setting `User=myuser`, the service executes with the privileges of that non-root user, reducing the attack surface and adhering to the principle of least privilege. This is the standard systemd mechanism for dropping root privileges for a service.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
AmbientCapabilities=CAP_NET_BIND_SERVICE
Why it's wrong here
This grants capabilities, not user identity.
DynamicUser=yes
Why it's wrong here
DynamicUser= creates a transient user, but the actual user is not 'myuser'.
User=myuser
Why this is correct
User= specifies the username or UID to run the service.
Related concept
Read the scenario before looking for a memorised answer.
Group=myuser
Why it's wrong here
Group= sets the group, but the user must also be specified.
Common exam traps
The trap here is that candidates often confuse `User=` with `Group=` or assume that `DynamicUser=yes` is the only way to run as a non-root user, missing that `User=` directly specifies a static, named user account.
Detailed technical explanation
Under the hood, systemd uses the `User=` directive to call `setuid()` (or `setresuid()`) after forking the service process, dropping all root privileges. A common subtlety is that if `User=` is set without also setting `Group=`, the service inherits the primary group of the specified user from `/etc/passwd`. In real-world scenarios, combining `User=` with `CapabilityBoundingSet=` and `AmbientCapabilities=` allows a non-root user to retain specific privileges (e.g., binding to low ports) while otherwise running unprivileged.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
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FAQ
Service Configuration — This question tests Service Configuration — Read the scenario before looking for a memorised answer..
The correct answer is: User=myuser — Option C is correct because the `User=` directive in a systemd unit file specifies the user (by name or UID) under which the service process runs. By setting `User=myuser`, the service executes with the privileges of that non-root user, reducing the attack surface and adhering to the principle of least privilege. This is the standard systemd mechanism for dropping root privileges for a service.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
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