CompTIA Linux+ (XK0-006)Services and User ManagementMedium
A system administrator needs to configure a `systemd` service named `myservice.service` to automatically restart whenever its main process exits unexpectedly (e.g., due to a crash). Which directive should be added to the `[Service]` section of the unit file?
- AExecReload=/bin/kill -HUP $MAINPID
- BRestart=on-failure
- CRemainAfterExit=yes
- DStartLimitIntervalSec=0
Show answer & explanationAnswer & explanation
Correct answer: B. Restart=on-failure
The `Restart=` directive in the `[Service]` section controls when and how `systemd` should restart a service. Setting it to `on-failure` ensures that the service is restarted only if it exits with a non-zero status code, is terminated by a signal (except `SIGHUP`, `SIGINT`, `SIGTERM`), or if a timeout occurs.
Why the other options are wrong
- A. `ExecReload=` specifies a command to run when the service is reloaded, not when it crashes and needs a full restart.
- C. `RemainAfterExit=yes` makes `systemd` consider a service active even after its main process exits, which is useful for `oneshot` services, but does not cause restarts.
- D. `StartLimitIntervalSec=` and `StartLimitBurst=` control how often `systemd` attempts to restart a service within a given timeframe to prevent a 'flapping' service from consuming resources, but do not *initiate* the restart policy.
systemd Restart Policies
The `Restart=` directive in a `systemd` service unit's `[Service]` section defines when `systemd` should automatically restart the service's main process.
- Common values: `no`, `on-success`, `on-failure`, `always`.
- `on-failure` restarts on non-zero exit code or signal.
- Prevents service downtime from crashes.
Memory trick: RESTART a service ON-FAILURE to keep it alive.