LFCS Service Configuration Practice Question
A service unit has the directive 'ExecStartPre=/bin/true' and 'ExecStart=/usr/bin/myapp'. What is the effect of ExecStartPre?
⚠ Common exam trap
Test-takers frequently confuse ExecStartPre with ExecStartPost or assume that a pre-start script failure is non-fatal, but systemd strictly enforces that a failed ExecStartPre prevents the service from starting unless explicitly configured otherwise.
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
✓
It runs a pre-start script; if it fails, the service is not started.
ExecStartPre is a systemd directive that specifies a command to run before the main ExecStart command. If the ExecStartPre command fails (returns a non-zero exit code), systemd will not proceed to start the service, unless the '-' prefix is used to ignore failure. Here, /bin/true always succeeds (exit code 0), so it does not block the service, but the directive itself is designed to enforce a pre-start check.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It sets an environment variable.
Why it's wrong here
Environment directives are used for that.
- ✗
It runs a post-start script.
Why it's wrong here
ExecStartPost runs after ExecStart.
- ✗
It runs a pre-start script; if it fails, the service still starts.
Why it's wrong here
Only if IgnoreFailure=yes is set.
- ✓
It runs a pre-start script; if it fails, the service is not started.
Why this is correct
ExecStartPre must exit with code 0 for the service to start.
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