XK0-005 Scripting, Containers and Automation Practice Test 3 — 15 Questions

Question 1

A DevOps engineer needs to run a container that executes a batch job and then exits. The container image is stored in a private registry. Which Docker command should be used to run the container and automatically remove it after it exits?

Accepted Answer

docker run --rm private.registry.com/batch:latest. The `docker run --rm` command automatically removes the container after it exits, which is ideal for batch jobs that should not leave behind stopped containers. The image reference `private.registry.com/batch:latest` pulls from a private registry when not cached locally. This combination ensures the container runs once, completes its task, and is cleaned up without manual intervention.

Answer

docker start --rm private.registry.com/batch:latest

Answer

docker run -d private.registry.com/batch:latest

Answer

docker exec --rm private.registry.com/batch:latest

Question 2

Which TWO statements are true regarding the use of Ansible for automation? (Choose TWO.)

Accepted Answer

Ansible playbooks are written in YAML.. Option B is correct because Ansible playbooks are written in YAML (YAML Ain't Markup Language), which is a human-readable data serialization standard. YAML allows for simple, declarative syntax to define automation tasks, variables, and handlers, making playbooks easy to write and maintain without requiring programming expertise.

Answer

Ansible requires a dedicated master server to manage nodes.

Answer

Ansible uses a pull-based model where nodes fetch configurations from a central server.

Answer

Ansible modules are written in Ruby.

Question 3

A pod in the Kubernetes cluster is in CrashLoopBackOff. Based on the exhibit, what is the most likely cause?

Accepted Answer

The application inside the container is crashing repeatedly.. The CrashLoopBackOff status indicates that a container in a pod is repeatedly crashing after starting. Kubernetes attempts to restart the container, but the application inside exits with a non-zero exit code, causing the restart loop. This is most commonly caused by the application itself crashing due to a bug, misconfiguration, or resource issue.

Answer

The container failed to start because of a missing configuration file.

Answer

The image pull failed due to authentication issues.

Answer

The container image is not available in the registry.

Question 4

A Linux administrator is responsible for a critical application that runs as a systemd service on a server. The application occasionally hangs, and the administrator wants to automate the restart if the service becomes unresponsive. The administrator writes a Bash script that checks if the service is active and responsive by pinging a local health endpoint. If the health check fails three consecutive times, the script restarts the service. The script is intended to run every minute via a cron job. However, after implementing the cron job, the service is restarted even when it is functioning correctly, causing unnecessary downtime. The administrator reviews the script and finds the following logic:

#!/bin/bash
SERVICE="myapp"
COUNT_FILE="/tmp/${SERVICE}_failcount"
if curl -f http://localhost:8080/health; then
    echo 0 > "$COUNT_FILE"
else
    FAILS=$(cat "$COUNT_FILE" 2>/dev/null || echo 0)
    FAILS=$((FAILS + 1))
    echo "$FAILS" > "$COUNT_FILE"
    if [ "$FAILS" -ge 3 ]; then
        systemctl restart "$SERVICE"
        echo 0 > "$COUNT_FILE"
    fi
fi

What is the most likely cause of the false restarts?

Accepted Answer

Multiple instances of the script are running concurrently due to cron timing, causing a race condition on the count file.. Option B is correct because the cron job runs the script every minute, but if the health check takes longer than a minute (e.g., due to network latency or a slow endpoint), multiple instances of the script can overlap. Each instance reads, increments, and writes the count file independently, causing a race condition where the fail count can be artificially inflated, leading to a false restart even when the service is healthy.

Answer

The count file is not being written because the script lacks write permissions to /tmp.

Answer

The script does not reset the count file after a successful health check.

Answer

The script does not handle the case where the count file does not exist on the first failure.

Question 5

A Linux administrator is creating a shell script to back up configuration files to a remote server. The script must ensure that if any command fails (e.g., rsync or tar), the script exits immediately and does not continue. Which TWO of the following should be included in the script to achieve this behavior? (Choose two.)

Accepted Answer

trap 'exit 1' ERR. Option A is correct because `trap 'exit 1' ERR` instructs the shell to execute `exit 1` whenever a command returns a non-zero exit status, which immediately terminates the script on any failure. Option D is correct because `set -e` causes the shell to exit immediately if any command (or pipeline, unless overridden) fails, providing a straightforward way to enforce fail-fast behavior in a backup script.

Answer

set -o pipefail

Answer

set -x

Answer

set -u

Question 6

A DevOps engineer is responsible for deploying a containerized web application on a Linux server running Docker. The application consists of three services: a frontend (Nginx), a backend (Node.js), and a database (PostgreSQL). The engineer uses Docker Compose to manage the stack. The deployment works correctly on a test environment, but when deployed to production, the frontend service fails to connect to the backend. Both services are on the same custom bridge network. The engineer checks the logs of the frontend container and sees 'getaddrinfo EAI_AGAIN backend-service'. The backend service is running and healthy. The engineer suspects a DNS resolution issue within the Docker network. Which of the following is the most likely cause and correct solution?

Accepted Answer

The frontend container is trying to resolve 'backend-service' but the backend container's hostname is different because the container_name is set in the docker-compose.yml.. Option A is correct because the frontend container is attempting to resolve 'backend-service' via Docker's embedded DNS, but the backend container's hostname may differ if the `container_name` directive is set in the docker-compose.yml. Docker Compose creates a default hostname equal to the service name unless overridden by `container_name`. If `container_name` is set to something like 'my-backend', the DNS entry for 'backend-service' will not exist, causing an `EAI_AGAIN` (temporary failure in name resolution) error. The solution is to either use the correct hostname (the service name) or set `container_name` to match the expected hostname.

Answer

The containers are not on the same network because the default network driver is 'host' instead of 'bridge'.

Answer

The backend service is listening on a different port than expected.

Answer

The Docker DNS resolver is caching an old IP address for the backend service.

Question 7

Drag and drop the steps to mount a new filesystem in the correct order.

Question 8

Drag and drop the steps to create and apply a systemd service unit in the correct order.

Question 9

Match each Linux command to its primary function.

Question 10

Match each Linux process signal to its typical action.

Question 11

A junior administrator is asked to automate the backup of a configuration file every night at 11 PM. The script /usr/local/bin/backup.sh already exists. Which command should the administrator run to schedule this task?

Accepted Answer

echo "0 23 * * * /usr/local/bin/backup.sh" | crontab -. Option C is correct because the `crontab -` command reads from standard input and installs the cron job. The line `0 23 * * * /usr/local/bin/backup.sh` specifies that the script should run at 23:00 (11 PM) every day, matching the requirement exactly. This is the standard method for scheduling recurring tasks in Linux using cron.

Answer

systemctl start backup.timer

Answer

at 23:00 /usr/local/bin/backup.sh

Answer

nohup /usr/local/bin/backup.sh &

Question 12

A system administrator wants to ensure that a container can access host devices such as USB drives. Which Docker run option should be used?

Accepted Answer

--device /dev/ttyUSB0. The `--device` flag in Docker allows a container to directly access a specific host device, such as `/dev/ttyUSB0` for a USB drive or serial adapter. This grants the container read/write permissions to the device node without requiring full privileged access, making it the precise and secure option for this requirement.

Answer

--privileged

Answer

--pid=host

Answer

--net=host

Question 13

An administrator is tasked with creating a systemd service that runs a Python script after the network is available. The script must restart automatically if it fails. Which systemd service unit directive should be used to ensure restart on failure?

Accepted Answer

Restart=on-failure. The `Restart=on-failure` directive instructs systemd to restart the service unit only when the process exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This is the correct choice because the requirement is to restart the script only if it fails, not unconditionally. Using `Restart=always` would restart the service even after a clean exit, which is unnecessary and could mask intentional stops.

Answer

Restart=always

Answer

RemainAfterExit=yes

Answer

RestartSec=5

Question 14

Which command will run a container in detached mode with the name 'web' and map host port 8080 to container port 80, using the nginx image?

Accepted Answer

docker run -d --name web -p 8080:80 nginx. Option A is correct because `docker run` creates and starts a new container. The `-d` flag runs it in detached mode (background), `--name web` assigns the name 'web', `-p 8080:80` maps host port 8080 to container port 80, and `nginx` specifies the image to use. This is the standard syntax for deploying a container with port mapping and a custom name.

Answer

docker exec -d --name web -p 8080:80 nginx

Answer

docker start -d --name web -p 8080:80 nginx

Answer

docker run -it --name web -p 8080:80 nginx

Question 15

An administrator needs to create a shell script that will be executed by a non-login shell. The script requires access to environment variables set in the user's profile. Which file should the script source to ensure these variables are available?

Accepted Answer

~/.bashrc. Option A is correct because ~/.bashrc is the file sourced by non-login interactive shells in Bash. When a script is executed by a non-login shell, it does not read ~/.bash_profile or ~/.profile; instead, it reads ~/.bashrc. By sourcing ~/.bashrc within the script, the administrator ensures that environment variables defined there (e.g., PATH, custom aliases) are available to the script.

Answer

/etc/profile

Answer

~/.profile

Answer

~/.bash_profile