LFCS Service Configuration Practice Question
A system administrator is managing a web application running as a systemd service on a new Linux server. The application requires a specific environment variable, DATABASE_URL, to be set before starting. The administrator has created a custom service unit file at /etc/systemd/system/webapp.service with the following content:
[Unit]
Description=Web Application Service
[Service]
ExecStart=/usr/local/bin/webapp Restart=on-failure
The administrator prefers to keep configuration separate from the unit file for easier updates. The service fails to start. Upon investigation, the administrator notices that the DATABASE_URL variable is not being passed to the process. What is the most appropriate course of action to ensure the environment variable is correctly set?
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
✓
Add EnvironmentFile=/etc/webapp.env in the [Service] section and place the variable in that file
Using EnvironmentFile allows the administrator to keep the DATABASE_URL variable in a separate file, which can be updated without modifying the unit file. Option A hardcodes the variable in the unit file, reducing flexibility. Option C only sets the variable in the current shell session and does not persist for the service. Option D modifies ExecStart but is less standard and less maintainable than using EnvironmentFile.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add an Environment directive in the [Service] section: Environment=DATABASE_URL=value
Why it's wrong here
Placing the value directly in the unit file contradicts the stated requirement to keep configuration separate, so updates would force unit edits and a daemon-reload. The Environment directive suits fixed, non-sensitive values shared by all instances; here an EnvironmentFile pointing at an external file supplies DATABASE_URL while preserving separation.
- ✓
Add EnvironmentFile=/etc/webapp.env in the [Service] section and place the variable in that file
Why this is correct
EnvironmentFile= satisfies the requirement to keep configuration outside the unit file, letting systemd read DATABASE_URL from /etc/webapp.env and inject it into the process environment at start. This is the native mechanism for separating variables from unit definitions.
- ✗
Export the DATABASE_URL variable in the shell before running systemctl start webapp
Why it's wrong here
systemd does not inherit variables exported in an interactive shell; the manager reads its own environment, so the service still starts without DATABASE_URL. It is tempting because exporting before launching a process works for foreground commands, and it would succeed if the service were started manually from that same shell session.
- ✗
Modify the ExecStart line to: ExecStart=/usr/bin/env DATABASE_URL=value /usr/local/bin/webapp
Why it's wrong here
Wrapping ExecStart in /usr/bin/env hardcodes the value into the unit file, defeating the stated goal of separating configuration from the unit. It is tempting because env is a familiar shell idiom for injecting variables, and it would work for a one-off command where no external configuration file is wanted.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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