XK0-006 Practice Test 48 — 15 Questions

Question 1

A junior Linux administrator needs to run a long-running backup script as the user 'backupuser' but currently has an active SSH session as 'adminuser'. The script should continue running even if the SSH session disconnects, and no output should be sent to the terminal. Which command should the administrator use?

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

Accepted Answer

sudo -u backupuser nohup /usr/local/bin/backup.sh > /dev/null 2>&1 &. The correct command combines sudo -u to run as backupuser, nohup to ignore hangup signals, and output redirection to /dev/null, with & to background it. This ensures the backup script continues after SSH disconnection and produces no terminal output, meeting both requirements precisely.

Answer

su backupuser -c '/usr/local/bin/backup.sh' &

Answer

screen -dmS backup sudo -u backupuser /usr/local/bin/backup.sh

Answer

at now + 0 minutes <<< 'sudo -u backupuser /usr/local/bin/backup.sh'

Question 2

A Linux administrator schedules a maintenance script with cron using the entry `30 2 * * 1 /usr/local/bin/backup.sh`. The script runs but produces no output and fails silently when executed by cron, though it works when run interactively. Which action best addresses the silent failure?

Accepted Answer

Redirect the script's stdout and stderr to a log file within the crontab entry or script.. Cron runs jobs with a minimal environment and no terminal, so interactive successes can become silent failures. Because cron only emails output when a mail transfer agent is configured, failures frequently vanish. Capturing stdout and stderr to a log file exposes the environment-related errors, such as an incomplete PATH or missing variables, that cause the discrepancy between interactive and scheduled execution.

Answer

Move the script to `/etc/cron.d/` so it inherits the system environment.

Answer

Add the `nohup` command before the script path in the crontab line.

Answer

Change the schedule to run every minute so the failure is observed sooner.

Question 3

A Linux administrator is packaging an internal automation tool as a container image and must ensure the resulting image is minimal, reproducible, and does not include a shell or package manager. Which TWO practices best support that goal? (Choose two.)

Accepted Answer

Build the application as a static binary and copy it into a scratch or distroless base image. Minimal container images combine a static or self-contained artifact with a base image that ships no shell or package manager, and multi-stage builds keep all compilation tooling out of the final layer. Together these practices produce small, reproducible images whose contents are limited to what the application needs at runtime, with no interactive tooling available to an attacker.

Answer

Add a RUN apk add --no-cache bash step so operators can exec into the container for debugging

Answer

Tag the image as latest and rebuild it nightly from the moving base image to keep it current

Answer

Run the container as root so the entrypoint can install missing packages at startup

Question 4

An administrator needs to schedule a backup script to run every Monday at 2:00 AM. Which crontab entry will accomplish this?

Accepted Answer

0 2 * * 1 /path/to/backup.sh. The correct crontab entry must set minute to 0, hour to 2, and day of week to 1 (Monday). The fields are minute, hour, day of month, month, day of week, command. The entry '0 2 * * 1 /path/to/backup.sh' satisfies these conditions and schedules the backup for every Monday at 2:00 AM.

Answer

2 0 * * 1 /path/to/backup.sh

Answer

0 2 * * 0 /path/to/backup.sh

Answer

0 2 1 * * /path/to/backup.sh

Question 5

A Linux administrator is configuring a systemd timer to run a maintenance script daily. The administrator creates maint.service and maint.timer unit files, then runs systemctl start maint.timer. The script does not run at the expected time. Which command should the administrator run to enable the timer so it starts automatically at boot and triggers on schedule?

Accepted Answer

systemctl enable maint.timer. A systemd timer must be enabled, not merely started, to be activated at boot. Enabling creates the appropriate symlink in the timer's target directory so systemd starts it automatically, and the timer then triggers the associated service according to its OnCalendar or OnUnitActiveSec schedule. Enabling the service or reloading the unit does not achieve persistent scheduled execution.

Answer

systemctl reload maint.timer

Answer

systemctl enable maint.service

Answer

systemctl daemon-reexec

Question 6

A Linux server reports that its root filesystem is 100 percent full, and applications are failing to write logs. The administrator needs to identify what is consuming space and reclaim it safely. Which two commands are appropriate to determine where the space is used? (Choose two.)

Accepted Answer

find / -xdev -type f -size +500M -exec ls -lh {} \;. Finding what filled the root filesystem requires two complementary views: per-directory totals to narrow the search, and a scan for unusually large individual files. Staying on one filesystem with -x and -xdev prevents mounted volumes from skewing results. Together these commands point the administrator to the exact data to review or remove.

Answer

lsblk -f

Answer

df -i /

Answer

fsck -n /dev/sda1

Question 7

A Linux administrator uses Ansible to manage a fleet of servers and needs to ensure a configuration file is present with specific contents on all web servers, restarting the service only when the file changes. Which Ansible module and handler pattern accomplishes this?

Accepted Answer

Use the `copy` module with a `notify` directive that triggers a handler containing the `service` module with `state: restarted`. Idempotent configuration management requires a module that reports change status and a handler that reacts to that status. The `copy` module writes the file and reports changed only on difference, and the `notify` directive invokes a handler that restarts the service. Unconditional shell restarts, `force: no`, or timestamp-only modules all fail to deliver a restart triggered specifically by a content change.

Answer

Use the `file` module with `state: touch` and a `cron` job to restart the service periodically

Answer

Use the `template` module with `force: no` and no handler, relying on the service to reload automatically

Answer

Use the `shell` module to run `systemctl restart httpd` after writing the file with a `command` task

Question 8

A Linux administrator needs to ensure that all user passwords meet a minimum length of 12 characters and include at least one uppercase letter, one lowercase letter, one digit, and one special character. Which file should be edited to enforce these password complexity requirements?

Accepted Answer

/etc/security/pwquality.conf. Password complexity requirements are enforced by the pam_pwquality module, which reads its configuration from /etc/security/pwquality.conf. This file allows setting parameters like minlen, ucredit, lcredit, dcredit, and ocredit to require specific character types and lengths. The other files serve different purposes and cannot enforce these rules.

Answer

/etc/pam.d/system-auth

Answer

/etc/login.defs

Answer

/etc/shadow

Question 9

A Linux administrator is configuring a server to use firewalld. The administrator wants to allow incoming traffic on TCP port 8080 only from the 192.168.1.0/24 subnet, while denying it from all other sources, without affecting other services. Which firewalld command should the administrator use to achieve this?

Accepted Answer

firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.1.0/24" port port="8080" protocol="tcp" accept'. Rich rules in firewalld allow combining source addresses, ports, and actions in a single rule. The correct syntax uses --add-rich-rule with a rule that specifies source address, port, protocol, and accept action. This precisely allows TCP 8080 from 192.168.1.0/24. Adding a port with a source argument is not supported, and adding a source to a zone does not restrict individual ports.

Answer

firewall-cmd --permanent --add-source=192.168.1.0/24 --add-port=8080/tcp

Answer

firewall-cmd --permanent --add-port=8080/tcp --source=192.168.1.0/24

Answer

firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.1.0/24" port port="8080" protocol="tcp" drop'

Question 10

After applying a kernel update, a Linux server boots but the root filesystem is mounted read-only, and dmesg shows I/O errors on /dev/sda2. The administrator needs to determine whether the filesystem is corrupted and, if so, repair it safely. Which sequence of actions should the administrator take?

Accepted Answer

Boot into rescue mode, run fsck -n on /dev/sda2 first, then run fsck -y if errors are reported.. A read-only root mount after I/O errors usually means the kernel detected filesystem problems and remounted defensively. Repair requires the filesystem to be offline, so rescue mode is appropriate. fsck -n first confirms and characterizes the damage without risk; if it reports errors, fsck -y applies repairs. Running fsck on a mounted filesystem, forcing a read-write remount, or reformatting are all unsafe or premature.

Answer

Recreate the filesystem with mkfs.ext4 /dev/sda2 and restore from the most recent backup.

Answer

Remount the root filesystem read-write with mount -o remount,rw / and continue using the server.

Answer

From the running system, run fsck -y /dev/sda2 immediately to repair the errors.

Question 11

A Linux administrator needs to parse a structured configuration file and extract the value of a specific key. The file format is JSON, and the administrator wants to use a command-line tool that is commonly preinstalled on modern Linux distributions. Which command should the administrator use?

Accepted Answer

jq. jq is purpose-built for JSON, understands the format's structure, and is commonly available on modern Linux distributions. It can extract a specific key with a simple filter and correctly handles nested data, escaping, and type conversions, making it the appropriate choice for parsing a JSON configuration file.

Answer

awk

Answer

grep

Answer

sed

Question 12

A Linux administrator is troubleshooting a service that fails to start. The service's unit file has a dependency on another service, but the dependent service is not running. The administrator wants to view the dependency tree of the failing service to understand the ordering and requirements. Which command should be used?

Accepted Answer

systemctl list-dependencies failing.service. systemctl list-dependencies is specifically designed to show the dependency tree of a unit, including which units are required or wanted and their current states. It provides a clear hierarchical view that helps diagnose why a service fails due to unmet dependencies. Other commands show status or logs but not the dependency structure.

Answer

systemctl cat failing.service

Answer

journalctl -u failing.service

Answer

systemctl status failing.service

Question 13

A new employee needs a user account on a Linux server. The administrator runs 'useradd -m jdoe' and then 'passwd jdoe'. After setting the password, the employee reports that they cannot log in via SSH. The administrator verifies the password is correct. Which file should the administrator check to ensure the account is not locked?

Accepted Answer

/etc/shadow. The /etc/shadow file holds the password hash and lock indicator. A locked account often has an exclamation mark or asterisk prepended to the password hash, which prevents authentication. Since the password was set correctly, the next step is to verify the account is not locked in /etc/shadow, for example by checking for a '!' prefix.

Answer

/etc/login.defs

Answer

/etc/group

Answer

/etc/passwd

Question 14

A Linux administrator is investigating why a scheduled backup job did not run overnight. The job is defined in the root user's crontab. Which command should the administrator use to review the cron daemon's log entries for the relevant time period?

Accepted Answer

journalctl -u cron --since "yesterday". To determine why a cron job did not execute, the administrator must examine the cron daemon's logs for the relevant period. On systemd-based distributions, cron is managed as a unit, so journalctl -u cron with a time filter surfaces start attempts, command errors, and skipped jobs. Listing the crontab or checking unrelated schedulers does not provide execution history.

Answer

crontab -l -u root

Answer

atq

Answer

systemctl list-timers --all

Question 15

A Linux administrator needs to grant the user 'jsmith' the ability to restart the httpd service without entering a password, while preventing all other sudo commands. The administrator creates the file /etc/sudoers.d/jsmith with the line: jsmith ALL=(root) NOPASSWD: /usr/bin/systemctl restart httpd. After saving the file, jsmith reports that sudo still prompts for a password. Which command should the administrator run to diagnose the issue?

Accepted Answer

sudo -l -U jsmith. The sudo -l -U jsmith command displays the sudo privileges for jsmith, including whether NOPASSWD is applied to the specified command. This directly shows if the rule in /etc/sudoers.d/jsmith is being read and matched, which is essential for troubleshooting why a password is still required.

Answer

journalctl -u sudo

Answer

visudo -c

Answer

grep jsmith /etc/sudoers