LFCS Service Configuration — Timed 20 Questions

Question 1

A system administrator configures a web server using systemd. After creating a custom service unit file, the administrator runs `systemctl daemon-reload` but the service still fails to start with a 'Unit not found' error. What is the most likely cause?

Accepted Answer

The unit file is placed in /usr/lib/systemd/system/ instead of /etc/systemd/system/.. The 'Unit not found' error after `systemctl daemon-reload` indicates that systemd cannot locate the unit file. Unit files in `/usr/lib/systemd/system/` are intended for distribution packages and are not automatically scanned by `daemon-reload` unless they are symlinked or the directory is explicitly included. The correct location for custom administrator-created unit files is `/etc/systemd/system/`, which is the primary location for locally managed units and is always included in the unit search path.

Answer

The administrator forgot to run `systemctl enable` before starting the service.

Answer

The administrator is not in the 'systemd' group.

Answer

The service name was misspelled in the `systemctl start` command.

Question 2

A server runs a custom application that listens on TCP port 8080. The administrator wants to ensure the application starts automatically on boot and restarts if it crashes. Which systemd unit file directive should be used to achieve the restart behavior?

Accepted Answer

Restart=on-failure. The `Restart=on-failure` directive in a systemd unit file instructs systemd to automatically restart the service unit when it exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This directly satisfies the requirement for the application to restart if it crashes, as a crash typically results in an unclean exit that triggers the restart condition.

Answer

RestartSec=5

Answer

Type=notify

Answer

RemainAfterExit=yes

Question 3

An administrator needs to configure a service to run as a non-root user for security reasons. Which systemd unit file directive accomplishes this?

Accepted Answer

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.

Answer

AmbientCapabilities=CAP_NET_BIND_SERVICE

Answer

DynamicUser=yes

Answer

Group=myuser

Question 4

A developer reports that a web application's logs are not being written to /var/log/myapp.log. The service runs as user 'myapp' and the log directory /var/log/myapp/ has permissions 755 owned by root. What is the most likely cause?

Accepted Answer

The service user 'myapp' does not have write permission to the log directory.. Option D is correct because the /var/log/myapp/ directory has permissions 755, which grants read and execute access to the 'others' category but not write. Since the service runs as user 'myapp', which is not the owner (root) and not in the root group, it falls under 'others' and thus lacks write permission. Without write permission on the directory, the service cannot create or write to /var/log/myapp.log, even if the file itself might have different permissions.

Answer

AppArmor is denying access.

Answer

SELinux is blocking the write.

Answer

The service is logging to systemd-journald instead of a file.

Question 5

An administrator wants to ensure that a custom service (myapp.service) starts only after the network is available and the PostgreSQL database service is running. Which systemd unit file directive should be used?

Accepted Answer

After=network.target postgresql.service. Option D is correct because the `After=` directive in a systemd unit file specifies ordering constraints, ensuring that `myapp.service` starts only after `network.target` and `postgresql.service` have reached the 'started' state. This does not create a dependency that forces those units to start; it only orders the startup sequence, which is exactly what the administrator needs to guarantee the service starts after the network and PostgreSQL are available.

Answer

Requires=network.target postgresql.service

Answer

Wants=network.target postgresql.service

Answer

BindsTo=network.target postgresql.service

Question 6

Which TWO statements are true about systemd service unit files? (Choose two.)

Accepted Answer

The [Service] section is mandatory for a service unit file.. Option C is correct because the [Service] section is mandatory in a systemd service unit file; without it, systemd cannot determine how to manage the service process. This section defines the service type, execution command, and other runtime parameters essential for the unit to function.

Answer

Environment variables can be loaded using EnvFile= directive.

Answer

The default service type is 'forking'.

Answer

The [Service] section must appear before the [Unit] section.

Question 7

Which THREE actions will affect the state of a systemd service that is currently running? (Choose three.)

Accepted Answer

systemctl kill myapp.service. Option A is correct because `systemctl kill myapp.service` sends a signal (default SIGTERM) to the main process of the running service, which can terminate or alter its state. This directly changes the service from a running state to a stopped or failed state depending on the signal and process behavior.

Answer

systemctl disable myapp.service

Answer

systemctl daemon-reload

Question 8

An administrator runs 'systemctl status sshd' and sees the output above. The administrator wants sshd to start automatically at boot. Which command should be used?

Accepted Answer

systemctl enable sshd. The `systemctl enable sshd` command creates the necessary symlinks in the systemd unit configuration directories (e.g., `/etc/systemd/system/multi-user.target.wants/`) so that the sshd service is started automatically at boot. This is the correct way to configure a service to start on boot in a systemd-based Linux distribution.

Answer

systemctl reenable sshd

Answer

systemctl mask sshd

Answer

systemctl start sshd

Question 9

A system administrator is configuring a custom systemd service that runs a Python script. The script logs output to stdout. The administrator wants to ensure that the service restarts automatically if it crashes, but only after a 10-second delay. Which directive should be added to the [Service] section of the unit file?

Accepted Answer

Restart=on-failure
RestartSec=10. Option B is correct because `Restart=on-failure` ensures the service restarts only when it exits with a non-zero exit code or is terminated by a signal (e.g., SIGKILL), which matches the 'crashes' scenario. Adding `RestartSec=10` introduces a 10-second delay before the restart attempt, as required. The other options either restart on success (irrelevant) or always restart (which would restart even on intentional stops), or omit the restart condition entirely.

Answer

Restart=on-success
RestartSec=10

Answer

Restart=always
RestartSec=10

Answer

RestartSec=10

Question 10

A Linux administrator needs to temporarily stop a service named 'httpd' without disabling it from starting automatically on subsequent boots. Which command should be used?

Accepted Answer

systemctl stop httpd. The `systemctl stop httpd` command sends a SIGTERM signal to the main process of the httpd service, causing it to stop immediately. This action does not modify the service's enablement state, so the service will still start automatically on subsequent boots if it is enabled. This is the correct way to temporarily stop a service without altering its boot-time behavior.

Answer

systemctl mask httpd

Answer

systemctl disable httpd

Answer

systemctl kill httpd

Question 11

A system administrator needs to ensure the Apache httpd service starts automatically on system boot. Which command should they use?

Accepted Answer

systemctl enable httpd. The `systemctl enable httpd` command creates the necessary symlinks in the systemd unit configuration directories (typically `/etc/systemd/system/multi-user.target.wants/`) to ensure the Apache httpd service starts automatically at boot time. This is the correct approach because `enable` configures the service to be started on system startup, whereas `start` only runs it immediately without affecting boot behavior.

Answer

systemctl start httpd

Answer

systemctl disable httpd

Answer

systemctl reload httpd

Question 12

Which TWO commands can be used to check the status of the sshd service on a system using systemd?

Accepted Answer

systemctl is-active sshd. Option B is correct because `systemctl is-active sshd` directly queries systemd to report whether the sshd service is currently in an active (running) state, returning a simple exit code and text output (e.g., 'active' or 'inactive'). Option E is correct because `systemctl status sshd` provides a comprehensive view of the service's current state, including whether it is active, its PID, recent log entries, and cgroup details, making it a standard command for checking service health on systemd-based systems.

Answer

systemctl list-units --type=service

Answer

systemctl is-enabled sshd

Answer

systemctl cat sshd

Question 13

A company runs a critical web application on a Linux server. The application is managed by a systemd service called 'myapp.service'. Recently, after a scheduled maintenance reboot, the service failed to start automatically. The administrator manually started it with 'systemctl start myapp' and it ran fine. The unit file is located at /etc/systemd/system/myapp.service and contains: [Unit] Description=MyApp After=network.target [Service] ExecStart=/usr/local/bin/myapp Restart=on-failure [Install] WantedBy=multi-user.target. The administrator wants to ensure the service starts automatically after future reboots. However, after running 'systemctl enable myapp', the service still didn't start after the next reboot. What is the most likely cause?

Accepted Answer

The service depends on a target that is not reached before the service starts, and 'Restart=on-failure' does not retry the start if the condition is not met.. Option B is correct because the 'After=network.target' directive only specifies ordering, not a requirement. If the network target is not fully reached before the service starts, systemd will attempt to start the service once and, if it fails, 'Restart=on-failure' will restart it only if the start was successful but the process later exits with a failure. It does not retry the initial start if a dependency condition is not met. The service must have 'Requires=network.target' or 'Wants=network.target' to ensure the target is active before the service starts.

Answer

The 'systemctl enable' command only creates symlinks; a separate 'systemctl start' must be run after enable.

Answer

The 'systemctl enable' command was not run as root.

Answer

The unit file has a syntax error that prevents systemd from parsing it.

Question 14

Order the steps to create a new partition on a disk using fdisk.

Question 15

Match each Linux process signal to its numeric value.

Question 16

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 17

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

Answer

The service is disabled

Question 18

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. Option D is correct because 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 19

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 20

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