LFCS Service Configuration Practice Test 5 — 15 Questions

Question 1

A system administrator manages a database server service (database.service) that experiences periodic CPU spikes, causing excessive load on the server. The administrator wants to limit the service's CPU usage to 25% of a single CPU core. The service is running on a system with cgroup v2. Which directive should be added to the [Service] section of the unit file to achieve this?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

CPUQuota=25%. In cgroup v2, the `CPUQuota=` directive in a systemd unit file directly limits the CPU time a service can use, expressed as a percentage of a single CPU core. Setting `CPUQuota=25%` restricts the service to using at most 25% of one core, which matches the administrator's requirement to cap CPU usage at 25% of a single core.

Answer

CPUAccounting=true

Answer

CPUWeight=100

Answer

CPUShares=256

Question 2

A system administrator needs to ensure that a custom service named 'myapp.service' starts automatically after a reboot and also restarts automatically no matter how the service stops, even if it exits normally. Which two actions should the administrator take? (Choose two.)

Accepted Answer

Run 'systemctl enable myapp.service' to enable the service.. Option B is correct because 'systemctl enable myapp.service' creates the necessary symlinks (typically under /etc/systemd/system/*.wants/) so systemd starts the unit automatically at boot, satisfying the reboot requirement. Option D is correct because 'Restart=always' in the [Service] section instructs systemd to restart the service regardless of exit status, including a clean exit code 0, which matches the requirement that it restart no matter how it stops. Option C is incorrect because 'Restart=on-failure' only restarts on non-zero exit codes, signals, or timeouts, so a normal exit would not trigger a restart. Option A is incorrect because 'systemctl mask' links the unit to /dev/null and prevents it from being started at all, the opposite of the desired behavior. Option E is incorrect because 'After=network.target' only orders startup relative to the network target and does not enable boot startup or automatic restarts.

Answer

Run 'systemctl mask myapp.service' to prevent manual stops.

Answer

Set 'Restart=on-failure' in the [Service] section of the service file.

Answer

Add 'After=network.target' to the [Unit] section of the service file.

Question 3

Refer to the exhibit. A Linux administrator sees that 'myapp.service' is in a failed state with exit status 1. To troubleshoot, which command should the administrator use to view the full error output that the service produced before exiting?

Accepted Answer

journalctl -u myapp.service. journalctl -u myapp.service retrieves the full log output for that systemd unit from the journal, including stdout/stderr captured before the service exited with status 1. This is the correct tool to see the complete error trace, not just the summary. systemctl status only shows a truncated tail and the exit code.

Answer

systemctl status myapp.service

Answer

systemctl reload myapp.service

Answer

systemctl restart myapp.service

Question 4

A system administrator needs to configure a new systemd service unit file for a custom application. The service should start after the network is fully online and requires the /opt/data directory to be mounted. Which section of the unit file should contain the After= and Requires= directives to define these dependencies?

Accepted Answer

[Unit]. Dependency and ordering directives such as After= and Requires= are placed in the [Unit] section because they describe the unit's relationships with other units and targets. The [Service] section is for execution parameters, [Install] for enabling, and [Path] for path units. Thus, [Unit] is correct.

Answer

[Path]

Answer

[Install]

Answer

[Service]

Question 5

A Linux administrator is configuring a custom systemd service that must not start until a network share is mounted. The mount is managed by a systemd mount unit named mnt-data.mount. Which directive should be added to the [Unit] section of the service unit to enforce this ordering?

Accepted Answer

After=mnt-data.mount. The service must wait for the mount unit to be active before starting. The After= directive explicitly defines ordering, ensuring the service starts only after mnt-data.mount has activated. Requiring the mount alone does not guarantee order, and Before= would reverse the desired sequence.

Answer

Before=mnt-data.mount

Answer

Wants=mnt-data.mount

Answer

Requires=mnt-data.mount

Question 6

A Linux administrator is managing a systemd service called app.service that runs a Java application. The service is configured with Restart=on-failure and RestartSec=5. After a recent update, the application crashes immediately upon start with exit code 1. The administrator notices that systemd keeps restarting the service every 5 seconds indefinitely. Which command should the administrator use to view the number of times the service has been restarted and the current restart limit status?

Accepted Answer

systemctl show app.service -p NRestarts -p StartLimitBurst -p StartLimitIntervalSec. To see the number of restarts and the restart limit configuration, systemctl show with specific properties is the correct tool. NRestarts gives the count, while StartLimitBurst and StartLimitIntervalSec define the rate limiting. Other commands provide logs or status but not these internal counters.

Answer

journalctl -u app.service -n 50

Answer

systemctl status app.service

Answer

systemctl list-units --state=failed

Question 7

A system administrator wants to change the default runlevel (target) of a Linux system from graphical.target to multi-user.target. Which command should they use?

Accepted Answer

systemctl set-default multi-user.target. The default target is set by the /etc/systemd/system/default.target symlink. The systemctl set-default command manages this symlink, pointing it to the desired target. isolate switches the current runtime state but does not persist. enable is for enabling units to start automatically, not for setting the boot target. Therefore, set-default is the correct command.

Answer

systemctl default multi-user.target

Answer

systemctl isolate multi-user.target

Answer

systemctl enable multi-user.target

Question 8

A system administrator needs to prevent a service named backup.service from starting automatically at boot, while keeping it available for manual start. The service is currently enabled. Which command should the administrator run?

Accepted Answer

systemctl disable backup.service. To prevent automatic startup while retaining the ability to start manually, the service must be disabled. Disabling removes the boot-time symlinks but leaves the unit file intact. Masking would prevent manual start, and stopping or killing only affects the current runtime state.

Answer

systemctl stop backup.service

Answer

systemctl mask backup.service

Answer

systemctl kill backup.service

Question 9

A Linux administrator is troubleshooting a custom systemd service named data-sync.service that repeatedly fails with the error 'start request repeated too quickly'. The unit file has Restart=always and RestartSec=5. Which command should the administrator use to reset the failed state and clear the restart counter so the service can be started again?

Accepted Answer

systemctl reset-failed data-sync.service. When a systemd service is configured with Restart=always and crashes repeatedly, systemd enforces a start limit (default 5 starts in 10 seconds) and then refuses further starts with the error 'start request repeated too quickly'. To recover, the administrator must clear the failed state and restart counter using systemctl reset-failed, after which the service can be started normally. This command is specifically designed for this purpose and is the correct tool for the scenario.

Answer

systemctl daemon-reload

Answer

systemctl restart data-sync.service

Answer

systemctl kill data-sync.service

Question 10

A junior administrator has written a custom systemd service unit file named backup.service in /etc/systemd/system/. The unit is intended to run a backup script once per day. After placing the file, the administrator runs systemctl start backup.service, but systemd reports 'Unit backup.service not found.' The file exists and has correct syntax. Which command should the administrator run to make systemd aware of the new unit file?

Accepted Answer

systemctl daemon-reload. systemd maintains an in-memory cache of unit files and does not watch /etc/systemd/system/ for new files. After adding or modifying a unit, systemctl daemon-reload must be run so systemd re-reads unit definitions and rebuilds dependencies. Only then does systemctl start recognize the new backup.service unit.

Answer

systemctl reload backup.service

Answer

systemctl reset-failed backup.service

Answer

systemctl enable backup.service

Question 11

A Linux administrator is configuring a custom systemd service called backup.service. The service should run a backup script only when the server is connected to AC power and not running on battery. Which condition directive should be added to the [Unit] section of backup.service?

Accepted Answer

ConditionACPower=true. ConditionACPower=true is the correct directive because it directly checks whether the system is running on AC power. When the system is on battery, the condition fails, and systemd skips the unit. This prevents the backup from running and draining battery. Other conditions check file existence, kernel command line, or capabilities, none of which reliably indicate AC power status.

Answer

ConditionKernelCommandLine=ac

Answer

ConditionCapability=CAP_SYS_ADMIN

Answer

ConditionPathExists=/sys/class/power_supply/AC/online

Question 12

A Linux administrator is configuring a systemd service that must only start after the network is fully online and must stop if the network goes down. The unit file currently has After=network.target. However, the service sometimes starts before DNS resolution is available, causing failures. Which target should the administrator use instead to ensure the network is fully configured and DNS is available?

Accepted Answer

network-online.target. network-online.target is designed specifically to wait until the network is fully operational, including DNS resolution. By using After=network-online.target and Wants=network-online.target, the service will not start until the network is truly online. This is the correct target for services that require actual network connectivity, unlike network.target which only signals that the network stack has started.

Answer

network.target

Answer

multi-user.target

Answer

basic.target

Question 13

A Linux administrator needs to modify the default runlevel (target) on a systemd-based Linux server so that it boots into a graphical environment by default. Which command should the administrator use?

Accepted Answer

systemctl set-default graphical.target. The default systemd target is controlled by the /etc/systemd/system/default.target symlink. The systemctl set-default command is the official way to change this symlink to point to the desired target, such as graphical.target for a graphical boot. Unlike isolate, which only changes the current state, set-default persists across reboots. Using enable is incorrect because it does not alter the default.target symlink. Manual symlink creation is possible but not the recommended practice.

Answer

systemctl enable graphical.target

Answer

ln -sf /usr/lib/systemd/system/graphical.target /etc/systemd/system/default.target

Answer

systemctl isolate graphical.target

Question 14

A system administrator needs to configure a systemd service so that it restarts automatically only when it exits with a non-zero exit code, but not when it is cleanly stopped by an administrator. The service unit file currently has no Restart directive. Which combination of directives should the administrator use?

Accepted Answer

Restart=on-failure and RestartSec=5. Restart=on-failure is the correct directive because it restarts the service only on abnormal termination, such as non-zero exit codes or signals. It does not restart on a clean stop, which matches the requirement. RestartSec=5 adds a delay to prevent tight restart loops. The other Restart values either restart too broadly (always) or too narrowly (on-abnormal, on-success).

Answer

Restart=always and RestartSec=5

Answer

Restart=on-success and RestartSec=5

Answer

Restart=on-abnormal and RestartSec=5

Question 15

A system administrator wants to view the current runtime status of the sshd.service, including whether it is active, its main PID, and recent log entries. Which command should they use?

Accepted Answer

systemctl status sshd.service. systemctl status sshd.service is the correct command because it provides a concise overview of the service's current state, including active/inactive, main PID, and the last few log lines. It combines status and recent logs in one output, exactly matching the administrator's need. Other commands either only show logs or only list units without detailed status.

Answer

systemctl show sshd.service

Answer

journalctl -u sshd.service -f

Answer

systemctl list-units --type=service | grep sshd