XK0-006 Practice Test 42 — 15 Questions

Question 1

A company is deploying a new web application using Docker containers. The application requires configuration values that vary between environments (development, staging, production). Which approach ensures the configuration is securely managed and applied without modifying the container image?

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

Accepted Answer

Pass configuration via environment variables and use Docker secrets for sensitive data.. Docker supports passing configuration via environment variables at runtime without altering the image, and Docker secrets securely manage sensitive data (e.g., passwords, API keys) by storing them in encrypted memory and mounting them as temporary files in `/run/secrets/`. This decouples configuration from the immutable image, adhering to the twelve-factor app methodology and ensuring environment-specific values are applied without rebuilding.

Answer

Build separate images for each environment with the configuration baked in.

Answer

Store configuration in a JSON file within the base image and override it at runtime.

Answer

Use a Dockerfile to copy the configuration file from the host at build time.

Question 2

A Linux system administrator is troubleshooting a server that runs a web application. Users report that the web application occasionally returns 503 Service Unavailable errors. The Apache web server appears to be running (systemctl status httpd shows active). The server has 8GB RAM and runs multiple applications. The administrator runs free -m and sees that swap usage is at 75% while available memory is very low. The top output shows that a process named 'databased' is consuming 40% of memory. The databased process is not a core application and is not needed for the web server. The administrator wants to resolve the issue without restarting the server. What should the administrator do?

Accepted Answer

Kill the databased process using kill -9. The immediate cause of the 503 errors is memory exhaustion: swap is at 75% and available RAM is critically low. The non-essential 'databased' process is consuming 40% of memory, starving Apache. Killing it with kill -9 frees that memory instantly, resolving the pressure without a restart. This directly addresses the root cause—a rogue process hogging RAM—rather than treating symptoms.

Answer

Enable the OOM killer to handle memory pressure automatically

Answer

Increase swap space by adding a swap file

Answer

Reduce Apache's MaxClients setting

Question 3

A Linux server is running low on disk space in the /var partition. The administrator runs 'du -sh /var/log/*' and finds that /var/log/syslog is 10 GB. Which of the following is the BEST long-term solution to prevent recurrence?

Accepted Answer

Configure logrotate to rotate and compress the syslog file daily.. Logrotate is the standard Linux utility for managing log file growth. By configuring logrotate to rotate and compress /var/log/syslog daily, the system automatically archives old logs and prevents a single file from consuming excessive disk space, addressing the root cause without manual intervention.

Answer

Manually truncate the syslog file with '> /var/log/syslog'.

Answer

Delete the syslog file and restart the syslog service.

Answer

Increase the log rotation frequency in /etc/logrotate.conf to monthly.

Question 4

A company runs a critical web application on a single server using Docker containers. The application consists of a web frontend container and a backend API container. Recently, the server ran out of disk space due to Docker logs and temporary images. The sysadmin is tasked with automating cleanup to prevent recurrence. The solution must not disrupt running containers. Which approach should be taken?

Accepted Answer

Configure log rotation for containers using `--log-opt max-size=10m` and `--log-opt max-file=3` in the Docker run command, and schedule `docker image prune -f` weekly.. It addresses both root causes: log growth and dangling images. Configuring `--log-opt max-size=10m` and `--log-opt max-file=3` limits container log file size and count without stopping containers, while `docker image prune -f` removes unused images safely. This combination prevents disk exhaustion without disrupting running containers, meeting all requirements.

Answer

Increase disk space by adding a new volume.

Answer

Create a script that stops all containers, removes unused images, and restarts containers.

Answer

Schedule a cron job to run `docker system prune -a -f` daily.

Question 5

Refer to the exhibit. The service fails to start with the error 'Failed to start My Service: Unit not found'. What is the most likely cause?

Accepted Answer

The service file is not in the correct directory.. The error 'Unit not found' indicates that systemd cannot locate the service unit file. Systemd service files must be placed in specific directories such as /etc/systemd/system/ or /usr/lib/systemd/system/. If the file is in the wrong directory, systemd will not recognize the unit, causing the 'Unit not found' error. Option B correctly identifies this as the most likely cause.

Answer

The User specified does not exist.

Answer

The network target is not reached.

Answer

The ExecStart script is missing.

Question 6

A user reports that a web server is unreachable. The administrator runs 'curl -I https://example.com' and gets no response. Which command should be used next to check if the server is reachable at the network level?

Accepted Answer

ping -c 4 example.com. The `curl -I` command failed to get a response, which could be due to a network-level issue rather than an application-layer problem. The `ping` command uses ICMP echo requests to test basic IP-level connectivity to the host, bypassing higher-layer protocols like HTTP/TLS. If the server is unreachable at the network layer, `ping` will show packet loss or timeouts, confirming a routing or firewall issue.

Answer

dig -x example.com

Answer

lsof -i :443

Answer

ss -tlnp | grep 443

Question 7

A system administrator is troubleshooting a network issue where a server cannot reach the internet. The server's IP address is 192.168.1.10/24, and the default gateway is 192.168.1.1. Which command should be used to verify the default gateway configuration?

Accepted Answer

ip route show. The `ip route show` command displays the kernel's IPv4 routing table, which includes the default gateway entry (destination 0.0.0.0/0 via 192.168.1.1). This directly verifies whether the default gateway is configured correctly for the server to reach external networks.

Answer

ip neigh show

Answer

ip addr show

Answer

ip link show

Question 8

An administrator is troubleshooting a service that fails to start. The administrator wants to view the last 50 lines of the service's journal log entries from the current boot. Which journalctl command should be used?

Accepted Answer

journalctl -u service -b -n 50. journalctl -u service -b -n 50 shows entries for the unit (-u), from current boot (-b), last 50 lines (-n 50).

Answer

journalctl -f -n 50 -u service

Answer

journalctl -u service --since today

Answer

journalctl -x -n 50 -u service

Question 9

An administrator wants to list all USB storage devices attached to the system. Which command provides this information?

Accepted Answer

lsblk. lsblk lists block devices; USB storage typically appears as sda, sdb, etc.

Answer

fdisk -l

Answer

lspci

Answer

lsusb

Question 10

A technician needs to check the current memory usage on a Linux system, including buffers and cache. Which command provides the most user-friendly output?

Accepted Answer

free -h. The `free -h` command displays memory usage in a human-readable format (e.g., KiB, MiB, GiB) and explicitly breaks down total, used, free, shared, buffers/cache, and available memory. This makes it the most user-friendly option for quickly assessing current memory usage including buffers and cache.

Answer

cat /proc/meminfo

Answer

iostat -m

Answer

vmstat -s

Question 11

A user wants to create a symbolic link to a file named 'original' in their home directory. Which command creates a symbolic link named 'link'?

Accepted Answer

ln -s original link. ln -s creates a symbolic link; order is target (existing file) then link name.

Answer

ln original link

Answer

ln -s link original

Answer

symlink original link

Question 12

Which command can be used to generate an SSH key pair for user authentication?

Accepted Answer

ssh-keygen. The `ssh-keygen` command is the standard tool for generating SSH key pairs (public and private keys) used for user authentication. It creates RSA, ECDSA, Ed25519, or DSA key files (e.g., `~/.ssh/id_rsa` and `~/.ssh/id_rsa.pub`) and supports options like `-t` for key type and `-b` for bit length, directly enabling passwordless login via public key authentication.

Answer

ssh-keyscan

Answer

ssh-copy-id

Answer

ssh-add

Question 13

An administrator wants to start a long-running script in the background so that it continues running even after logging out. Which command should be used?

Accepted Answer

nohup script.sh &. nohup prevents the process from receiving SIGHUP when the terminal closes. & runs it in background.

Answer

script.sh &

Answer

nohup script.sh

Answer

bg script.sh

Question 14

A developer wants to change all occurrences of 'foo' to 'bar' in a configuration file and save the changes in-place. Which sed command should be used?

Accepted Answer

sed -i 's/foo/bar/g' file. sed -i 's/foo/bar/g' file performs an in-place global substitution. The -i flag edits the file directly.

Answer

sed -i 's/foo/bar/' file

Answer

sed -n 's/foo/bar/p' file

Answer

sed 's/foo/bar/g' file

Question 15

A Linux server is booting but stops at a prompt with the message 'Give root password for maintenance'. Which systemd target is the system likely trying to reach?

Accepted Answer

emergency.target. emergency.target gives a single-user root shell with minimal services. rescue.target also gives a shell but with more services loaded. The prompt 'Give root password for maintenance' is typical of emergency mode.

Answer

graphical.target

Answer

multi-user.target

Answer

rescue.target