LFCS Service Configuration Practice Test 2 — 15 Questions

Question 1

Which command enables a service to start automatically at boot in a systemd-based system?

Accepted Answer

systemctl enable service. The `systemctl enable` command creates the necessary symlinks in the `/etc/systemd/system/` directory tree (typically `multi-user.target.wants/`) to ensure the specified service unit is started automatically when the system boots. This is the standard mechanism in systemd to configure a service for automatic startup at boot time.

Answer

systemctl set-default service

Answer

systemctl daemon-reload

Answer

systemctl start service

Question 2

A custom systemd service unit file has been created but the service fails to start with 'Exec format error'. What is the most likely cause?

Accepted Answer

The ExecStart command path is incorrect or missing shebang. The 'Exec format error' in systemd indicates that the binary or script specified in the ExecStart directive cannot be executed, typically because the path is incorrect, the file is not executable, or (most commonly) the script lacks a valid shebang line (e.g., #!/bin/bash). Without a shebang, the kernel does not know which interpreter to use, causing an execve() failure.

Answer

The unit file has incorrect permissions

Answer

The user does not have permission to start the service

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The service is disabled

Question 3

An administrator configures a systemd service with Restart=on-failure and RestartSec=10. What happens if the service exits with a non-zero exit code?

Accepted Answer

It waits 10 seconds before restarting. When Restart=on-failure is set, systemd only restarts the service if it exits with a non-zero exit code or is terminated by a signal (excluding SIGHUP, SIGINT, SIGTERM, and SIGPIPE). The RestartSec=10 directive then introduces a 10-second delay before the restart attempt, preventing rapid restart loops and giving the system time to stabilize.

Answer

It restarts immediately

Answer

It retries infinitely regardless of exit code

Answer

It does not restart

Question 4

To check the details of a failed systemd service unit, including the last log entries, which command is most appropriate?

Accepted Answer

systemctl status service. `systemctl status service` is the most appropriate command because it displays the current state of the service unit, including whether it is active, failed, or inactive, along with the last several log entries from the journal for that unit. This provides both the failure status and the contextual log output needed to diagnose why the service failed, all in a single command.

Answer

systemctl list-units --failed

Answer

systemctl is-failed service

Answer

systemctl show service

Question 5

A service is configured to run as a specific user. Which directive in the [Service] section sets the user?

Accepted Answer

User. In systemd service units, the directive to specify the user under which the service process runs is `User=` within the `[Service]` section. This directive sets the Unix user account (by name or UID) that the service's main PID will execute as, ensuring proper privilege separation and security.

Answer

RunAs

Answer

Account

Answer

UserID

Question 6

Which systemd unit type is used to group services and other units together for boot execution?

Accepted Answer

target. In systemd, the 'target' unit type is designed to group services, sockets, timers, and other units into a logical synchronization point for boot execution. Targets do not execute code themselves but instead define dependencies (via Wants, Requires, and After directives) that ensure all associated units are started in the correct order to reach a desired system state, such as multi-user.target or graphical.target.

Answer

socket

Answer

timer

Answer

service

Question 7

A system administrator wants to limit the CPU usage of a service. Which systemd resource control directive should be used?

Accepted Answer

CPUAccounting=yes and CPUQuota. To limit CPU usage in systemd, you must first enable CPU accounting with `CPUAccounting=yes` to track CPU consumption, and then set `CPUQuota` to specify a maximum percentage of CPU time the service can use. Without `CPUAccounting=yes`, the `CPUQuota` directive is ignored by systemd, making the combination essential for enforcing a hard CPU limit.

Answer

CPUShares

Answer

CPUQuota

Answer

CPULimit

Question 8

To ensure a service starts only after /var/lib/mysql is mounted, which directive should be used in the unit file?

Accepted Answer

After=var-lib.mount. The `After=` directive in a systemd unit file specifies that the current unit should start only after the listed units have been activated. By setting `After=var-lib.mount`, the service will wait until the mount unit for `/var/lib/mysql` is fully mounted before starting, ensuring the required filesystem is available.

Answer

Requires=/var/lib/mysql

Answer

BindsTo=var-lib.mount

Answer

Before=var-lib.mount

Question 9

A service that was once enabled is now failing to start. The administrator wants to immediately disable it to prevent boot delays. Which command sequence is correct?

Accepted Answer

systemctl disable --now service. `systemctl disable --now service` both stops the service immediately and disables it from starting at boot in a single atomic command. This is the most efficient way to prevent boot delays caused by a failing service, as it combines the stop and disable actions without relying on shell operators that could fail if the first command exits with a non-zero status.

Answer

systemctl disable service ; systemctl stop service

Answer

systemctl stop service && systemctl disable service

Answer

systemctl mask service

Question 10

Which TWO commands can be used to check the status of a service?

Accepted Answer

service status. The `service` command is a legacy SysV init wrapper that can query the status of a service by calling the appropriate init script with the `status` argument. It remains available on many Linux distributions for backward compatibility, making it a valid tool to check service status.

Answer

systemd-analyze

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start stop restart

Answer

initctl status

Question 11

Which TWO directives are typically used in a systemd service unit file to configure dependencies?

Accepted Answer

Wants. B is correct because the `Wants` directive in a systemd service unit file specifies a weaker dependency: the listed units are started if possible, but the current unit will still activate even if they fail. E is correct because the `Requires` directive creates a stronger dependency: the listed units must be successfully started for the current unit to start; if they fail, the current unit is deactivated. Both are fundamental for defining service dependencies in systemd.

Answer

After

Answer

Before

Answer

Alias

Question 12

Which THREE of the following are valid systemd unit types?

Accepted Answer

target. 'target' is a standard systemd unit type used to group other units together, similar to runlevels in SysVinit. Targets are defined in .target files and are essential for defining synchronization points during system boot or service state transitions.

Answer

notification

Answer

startup

Question 13

Based on the exhibit, what is the correct interpretation?

Accepted Answer

The service is running but the unit file has been modified recently and needs reloading. The 'daemon-reload' notice in the systemctl status output indicates that the unit file has been modified on disk but systemd has not yet reloaded its configuration. Running 'systemctl daemon-reload' will re-read the unit files and apply the changes, which is why option C is correct.

Answer

The service is inactive

Answer

The configuration file is corrupt

Answer

The service is failing

Question 14

Which of the following statements is true about this unit?

Accepted Answer

The service will be restarted indefinitely with a 10-second delay between restarts regardless of exit status. The `Restart=always` directive in a systemd service unit causes the service to be restarted indefinitely regardless of the exit status, and the `RestartSec=10` directive introduces a 10-second delay between each restart attempt. This behavior is defined in the systemd.service(5) man page, where `Restart=always` triggers a restart for any exit reason, including clean exits or signals.

Answer

The service can be started by a timer unit

Answer

The service will start automatically at boot only if network-online.target is reached

Answer

The service requires SELinux context

Question 15

What can be concluded from the log?

Accepted Answer

SSH server failed to start due to configuration error. The log shows that the SSH service failed to start because of a configuration error. Specifically, the log entry indicates a syntax error or invalid directive in the SSH daemon configuration file (typically /etc/ssh/sshd_config), which prevents the service from binding to the port and starting. This is a common issue when editing the configuration file manually, as the SSH daemon validates its configuration at startup and will refuse to run if any errors are found.

Answer

SSH server is masked

Answer

SSH server is running with errors

Answer

SSH server stopped normally