XK0-005 Scripting, Containers and Automation — 100 Questions

Question 1

A DevOps engineer needs to ensure that a containerized web application always restarts automatically if the container exits unexpectedly. Which Docker run option should be used?

Accepted Answer

--restart=always. The `--restart=always` policy ensures that the container restarts regardless of the exit code or reason for termination, including unexpected crashes. This is the correct choice for a containerized web application that must maintain high availability by automatically recovering from any unexpected exit.

Answer

--restart=on-failure

Answer

--restart=unless-stopped

Answer

--restart=no

Question 2

A system administrator wants to create a new user and set a password in a single command as part of a provisioning script. Which command accomplishes this?

Accepted Answer

echo 'user1:password' | chpasswd. Option B is correct because the `chpasswd` command reads username:password pairs from standard input, allowing a single command to create or update a user's password. When combined with `echo`, it sets the password for a new or existing user in one line, which is ideal for provisioning scripts. The `-p` option in `useradd` expects an already-hashed password, not a plaintext one, and `passwd` does not accept the password as an argument for security reasons.

Answer

passwd user1 password

Answer

useradd -m -p password user1

Answer

usermod -p password user1

Question 3

A Linux server that hosts a critical database application has been experiencing occasional kernel panics. The administrator wants to ensure the system automatically reboots after a panic and logs the crash dump. Which sysctl parameter should be set?

Accepted Answer

kernel.panic = 10. Option D is correct because setting `kernel.panic = 10` instructs the Linux kernel to wait 10 seconds after a kernel panic before automatically rebooting. This ensures the system recovers without manual intervention, and combined with a configured crash dump mechanism (e.g., kdump), the crash dump is captured before the reboot.

Answer

kernel.panic_on_warn = 10

Answer

kernel.panic_on_oops = 10

Answer

kernel.panic_print = 10

Question 4

A developer wants to run a container with a specific command that overrides the default entrypoint. Which Docker command should be used?

Accepted Answer

docker run --entrypoint /bin/bash myimage. Option C is correct because the `--entrypoint` flag in `docker run` allows you to override the default entrypoint defined in the Docker image. By specifying `--entrypoint /bin/bash`, the container will start with `/bin/bash` as its entrypoint, ignoring any `ENTRYPOINT` or `CMD` instructions in the Dockerfile. This is the standard Docker syntax for replacing the entrypoint at runtime.

Answer

docker run myimage /bin/bash

Answer

docker exec myimage /bin/bash

Answer

docker start myimage /bin/bash

Question 5

A senior administrator is troubleshooting a shell script that fails to execute properly. The script starts with #!/bin/bash and has execute permissions. Which of the following could cause the script to fail to run when invoked as ./script.sh?

Accepted Answer

The script contains carriage return characters (\r).. Option B is correct because carriage return characters (\r) are a common issue when scripts are edited on Windows and then transferred to Linux. The shebang line #!/bin/bash expects a Unix-style line ending (LF), but \r characters cause the shell to interpret the command interpreter as '/bin/bash\r', which is not a valid executable path. This results in a 'No such file or directory' error when the script is invoked as ./script.sh, even though permissions are correct.

Answer

The shebang line is not on the first line.

Answer

The script uses #!/bin/sh instead of bash.

Answer

The script starts with a byte order mark (BOM).

Question 6

A cloud engineer needs to automate the deployment of a new virtual machine with a specific configuration using Ansible. Which file format is typically used for Ansible playbooks?

Accepted Answer

YAML. Ansible playbooks are written in YAML (YAML Ain't Markup Language) because it is human-readable, supports complex data structures like lists and dictionaries, and is designed for configuration management. YAML's indentation-based syntax aligns with Ansible's declarative approach, allowing tasks, variables, and handlers to be defined cleanly without the overhead of brackets or tags.

Answer

JSON

Answer

XML

Answer

INI

Question 7

A developer is writing a Bash script that must be portable across different Linux distributions. The script needs to check if a package is installed. Which command should be used to achieve this portability?

Accepted Answer

command -v package. The `command -v package` command is the most portable way to check if a package is installed across different Linux distributions because it uses the POSIX-standard `command` shell built-in, which works in any Bourne-compatible shell (bash, sh, dash, etc.) regardless of the underlying package manager. It returns the path to the executable if the package's binary is in the PATH, or nothing if it is not installed, making it distribution-agnostic.

Answer

which package

Answer

dpkg -l package

Answer

rpm -q package

Question 8

A junior administrator needs to view the logs of a running container named 'webapp'. Which command should be used?

Accepted Answer

docker logs webapp. The `docker logs webapp` command retrieves the stdout and stderr output streams from the container's main process, which is the standard way to view logs for a running or stopped container. This is the correct approach because Docker captures these streams and stores them in a JSON file on the host, accessible via the `docker logs` command.

Answer

docker attach webapp

Answer

docker inspect webapp

Answer

docker stats webapp

Question 9

A Linux administrator is writing a script that must wait for a background process to finish before continuing. The process ID is stored in a variable. Which command should be used to wait for this process?

Accepted Answer

wait $PID. Option C is correct because the `wait` command in Bash, when given a specific process ID (PID), suspends execution of the calling shell script until that background process terminates. This directly fulfills the requirement to wait for a specific background process whose PID is stored in a variable.

Answer

sleep 10

Answer

wait

Answer

kill -0 $PID

Question 10

A systems administrator wants to build a custom Docker image from a Dockerfile located in the current directory. Which command should be used?

Accepted Answer

docker build .. The `docker build .` command reads the Dockerfile from the current directory and builds a custom Docker image from its instructions. This is the standard command for building an image from a Dockerfile, where the dot represents the build context (the current directory).

Answer

docker create .

Answer

docker commit .

Answer

docker image build .

Question 11

Which TWO of the following are valid methods to pass environment variables to a Docker container at runtime?

Accepted Answer

Using the -e flag with docker run. Option A is correct because the `-e` flag (or `--env`) with `docker run` allows you to set environment variables directly on the command line, e.g., `docker run -e MY_VAR=value`. This is a standard and widely used method to pass environment variables at runtime without modifying the image.

Answer

Using the ENV instruction in the Dockerfile

Answer

Using the --environment flag with docker run

Answer

Using the --env flag with docker run

Question 12

A Linux administrator needs to implement a cron job that runs a script every day at 2:30 PM. Which TWO cron schedule expressions are equivalent?

Accepted Answer

30 14 * * *. In cron syntax, the first field is minute (0-59), the second is hour (0-23) in 24-hour format. 2:30 PM corresponds to hour 14 in 24-hour time. Therefore, '30 14 * * *' correctly specifies the job runs at minute 30 of hour 14 every day. Option A and E are identical and both use the correct 24-hour representation.

Answer

30 2 * * * PM

Answer

30 2 * * *

Answer

30 2 * * *

Question 13

Which THREE of the following are valid systemd unit types?

Accepted Answer

timer. A is correct because `timer` is a valid systemd unit type used to schedule and trigger other units (typically services) based on time events, similar to cron but integrated with systemd. Timers can be monotonic (relative to system events) or real-time (calendar-based), and they are defined in `.timer` files.

Answer

system

Answer

cron

Question 14

A developer is writing a shell script that needs to handle errors. Which THREE of the following are best practices for robust script error handling?

Accepted Answer

Check the exit code of commands using $?. Option B is correct because checking the exit code of commands using `$?` allows the script to conditionally handle failures based on the specific return value of each command. This is a fundamental error-handling technique in shell scripting, as every command returns an exit code (0 for success, non-zero for failure), and inspecting `$?` immediately after a command lets the developer decide how to respond to that specific error.

Answer

Ignore errors to simplify the script

Answer

Use set +e to allow the script to continue on error

Question 15

Based on the exhibit, what is the most likely cause of the repeated connection refused errors?

Accepted Answer

The database service is down.. The 'connection refused' error indicates that the client's TCP SYN packet reached the target host on port 3306, but the host actively rejected the connection because no process is listening on that port. This is the classic symptom of the MySQL/MariaDB database service being stopped or crashed, as the OS TCP stack sends an RST packet when a connection attempt hits a port with no listening socket.

Answer

The DNS resolution for the database host fails.

Answer

A firewall is blocking port 3306.

Answer

The database credentials are incorrect.

Question 16

After building and running the container as shown in the exhibit, the administrator tries to access http://localhost:8080 but receives a connection refused error. What is the most likely cause?

Accepted Answer

The container exited immediately after starting.. The most likely cause is that the container exited immediately after starting. When a container runs a command that finishes quickly (e.g., a shell script that exits), the container stops, and no process listens on port 8080. This results in a 'connection refused' error because the container is no longer running to accept connections.

Answer

The port mapping is incorrect.

Answer

The base image is not compatible.

Answer

The CMD syntax is incorrect.

Question 17

Based on the exhibit, how often does the healthcheck.sh script run?

Accepted Answer

Every 5 minutes. The cron expression `*/5 * * * *` in the crontab file means the script runs every 5 minutes. The `*/5` in the minute field triggers execution every 5 minutes, while the asterisks in the hour, day, month, and weekday fields mean every hour, every day, every month, and every day of the week, respectively.

Answer

Every 5 days

Answer

Every 5 hours

Answer

Every 5 seconds

Question 18

A company runs a critical web application on a single Linux server. The application consists of a Node.js backend and a PostgreSQL database. The server is running out of disk space frequently due to application logs. The administrator wants to implement a log rotation solution that is automated, minimizes data loss, and compresses old logs. The administrator has root access and wants to use built-in tools. Currently, logs are written to /var/log/app/access.log and /var/log/app/error.log. The application never closes its log files. Which of the following is the best course of action?

Accepted Answer

Configure logrotate with daily rotation, compression, and the copytruncate option.. Option C is correct because logrotate with the copytruncate option allows the log file to be rotated without requiring the application to close or reopen its file handles. This is essential since the application never closes its log files. Daily rotation with compression addresses the frequent disk space issue while minimizing data loss, and logrotate is a built-in Linux tool that runs automatically via cron.

Answer

Configure the systemd journal to capture the application logs and set MaxRetentionSec.

Answer

Create a cron job that runs every hour to move the logs to a backup directory and restart the application.

Answer

Configure logrotate with a weekly rotation and no copytruncate, since the application will eventually close the log files.

Question 19

A development team uses Git for version control and wants to automate the testing of every commit pushed to the repository. They have a Jenkins server running on a Linux machine. The team wants to automatically trigger a Jenkins pipeline job whenever a push is made to the main branch of their Git repository. The Jenkins server is behind a firewall and cannot be accessed from the internet. The Git repository is hosted on a private GitHub repository. Which of the following is the best approach to trigger the Jenkins job automatically?

Accepted Answer

Configure Jenkins to poll the Git repository every minute for changes.. Option B is correct because Jenkins' polling mechanism allows it to periodically check the Git repository for changes, which works even when the Jenkins server is behind a firewall and cannot receive inbound webhooks. Polling every minute provides near-real-time automation without requiring internet access to the Jenkins server, making it the only viable option given the network constraint.

Answer

Have developers manually click 'Build Now' in Jenkins after each push.

Answer

Configure a GitHub webhook to send a POST request to the Jenkins server.

Answer

Set up a cron job on the Git server to execute a script that triggers Jenkins.

Question 20

An administrator needs to deploy a containerized web application on a Linux server. The application requires port 8080 to be mapped to host port 80. Which command will run the container in detached mode with this port mapping?

Accepted Answer

docker run -d -p 80:8080 webapp. Option D is correct because the `-d` flag runs the container in detached mode, and `-p 80:8080` maps host port 80 to container port 8080, which matches the requirement. The syntax is `-p host_port:container_port`, so `-p 80:8080` correctly exposes the application's container port 8080 on the host's port 80.

Answer

docker run -p 80:8080 webapp

Answer

docker run -d -p 8080:80 webapp

Answer

docker run -d -p 8080:80 webapp