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| Certification Vendor: | Linux Foundation |
|---|---|
| Exam Name: | Linux Foundation Certified System Administrator (LFCS) Exam |
| Exam Number: | LFCS |
| Exam Price: | USD 300 |
| Exam Duration: | 120 minutes |
| Passing Score: | Approximately 66% (performance-based scoring) |
| Available Languages: | English |
| Exam Format: | Hands-on lab tasks in a live Linux environment, Performance-based practical exam, Proctored online exam |
| Related Certifications: | Linux Foundation Certified Engineer (LFCE) |
| Certificate Validity Period: | 3 years |
| Real Exam Qty: | Performance-based tasks (typically ~12–17 hands-on tasks) |
| Recommended Training: | Linux Foundation LFCS Training Courses |
| Exam Registration: | Linux Foundation Certification Registration |
| Sample Questions: | Linux Foundation LFCS Sample Questions |
| Exam Way: | Online, remotely proctored performance-based exam in a live Linux environment |
| Pre Condition: | No strict prerequisites, but strong Linux command-line experience is recommended. |
| Official Syllabus URL: | https://training.linuxfoundation.org/certification/linux-foundation-certified-sysadmin-lfcs/ |
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The LFCS Certification Exam is a vendor-neutral certification that validates the skills and knowledge required for a system administrator to manage Linux systems. It is designed to assess an individual's ability to perform tasks such as configuring, maintaining, and troubleshooting Linux systems, as well as installing and configuring software, managing user accounts, and securing Linux systems.
NEW QUESTION # 50
Which of the following commands replaces each occurrence of 'bob' in the file letter with 'Bob' and writes the result to the file newletter?
Answer: E
NEW QUESTION # 51
When using rpm --verify to check files created during the installation of RPM packages, which of the following information is taken into consideration? (Choose THREE correct answers.)
Answer: A,D,E
NEW QUESTION # 52
Task
First, build the Dockerfile located at ~/flying-jay/Dockerfile, tagging the container image as myapp:latest.
Next, start a detached container using the built image tagged myapp:latest, mapping the container port 80/tcp to host port 8080/tcp and limiting the memory usage to 256m.
Finally, ensure that the container is started automatically on boot or restart of Docker.
Answer:
Explanation:
See the complete solution in Explanation.
Explanation:
Objective: Build a Docker image from the existing Dockerfile, create and start a container in detached mode, configure its network port mapping and memory limit, and ensure Docker automatically restarts the container following a Docker daemon restart or system reboot.
The task requires four specific configurations:
Requirement
Correct configuration
Docker image
myapp:latest
Container execution
Detached (-d)
Port mapping
Host 8080/tcp # Container 80/tcp
Memory limit
256m
Automatic restart
--restart=always
The essential Docker commands are:
Docker's official documentation confirms the behavior of the image-building, container-execution, memory- limit, port-publishing and restart-policy options used here.
Docker Docs
+2
Step 1: Connect to the correct Linux server.
The video specifies host lfcs00096.
From the candidate terminal, execute:
This connects to the Linux host where the Docker image and container must be created.
All subsequent commands must be executed on this host.
Step 2: Verify that Docker is installed.
Execute:
This displays the installed Docker client version.
For example:
The actual version may differ.
Check whether the Docker daemon is accessible:
This reports information about the Docker Engine, including its version, storage driver, available resources and container runtime.
If the Docker daemon is unavailable, investigate the service before proceeding.
Step 3: Verify that the Docker service is running.
Execute:
A running service should report:
For a concise check:
Expected:
If Docker is installed but stopped, start it:
There is no reason to reinstall Docker if the existing installation is functioning.
Step 4: Navigate to the Dockerfile directory.
The task specifies:
Execute:
Verify the working directory:
Then inspect its contents:
The directory should contain the Dockerfile and any files required to build the application.
Step 5: Verify that the Dockerfile exists.
Execute:
You can also confirm that it is a regular file:
An exit status of 0 indicates that the file exists.
The Dockerfile is already provided. There is no requirement to create a new Dockerfile or replace its contents.
Step 6: Inspect the Dockerfile before building.
Execute:
A Dockerfile can contain instructions such as:
Instruction
Purpose
FROM
Specifies the base image
RUN
Executes commands during image creation
COPY
Copies files from the build context into the image
WORKDIR
Sets the working directory
EXPOSE
Documents an intended container listening port
CMD
Specifies a default startup command
ENTRYPOINT
Defines the executable launched by the container
The Dockerfile may already configure a web service to listen on port 80.
Do not invent or replace application commands, because the task requires building the existing Dockerfile.
Step 7: Understand the Docker build context.
The Docker build context is the collection of files available to the Docker builder.
Because the Dockerfile is located at:
the normal build context is:
After navigating into that directory, the build context is represented by:
Docker's official documentation confirms that the final positional argument of docker build defines the build context.
Docker Docs
Step 8: Build the Docker image with the exact required tag.
Execute:
This is the first essential Docker command.
sudo provides access to the Docker daemon.
docker build builds an image from a Dockerfile.
-t assigns a repository name and image tag.
myapp:latest is the exact image reference specified in the task.
indicates the current directory as the build context.
An equivalent command, when executed from another directory, would be:
However, the shorter command is preferable after changing into ~/flying-jay.
Step 9: Examine the build output.
During the build, Docker processes the Dockerfile instructions.
A successful build may display output similar to:
This is illustrative.
The actual build output depends on the contents of the Dockerfile, Docker Engine version and BuildKit configuration.
After the command completes, check the exit status:
Expected:
If the build fails, inspect the reported error before proceeding. Common causes include an unavailable base image, missing build-context files or a failing Dockerfile instruction.
Step 10: Verify that the image was created successfully.
Execute:
The output should contain an entry corresponding to:
For more specific verification:
If the image exists, Docker returns its metadata.
If the image does not exist, Docker reports an error.
Do not create a container until the image has been built successfully.
Step 11: Check whether an existing container will conflict.
The task does not specify a required container name. For easier management, the solution will use:
Before creating the container, execute:
Check whether a container named myapp already exists.
If an existing container has that name, inspect it rather than automatically deleting it. Docker container names must be unique.
Using --name myapp is optional for the assessment; it is a convenient identifier for verification.
Step 12: Start the container in detached mode with all required options.
Execute:
This is the second essential command and implements all requested runtime requirements.
Parameter
Purpose
docker run
Creates and starts the container
-d
Runs the container in detached mode
--name myapp
Assigns a convenient container name
--restart=always
Configures automatic restarts
-p 8080:80/tcp
Maps host TCP 8080 to container TCP 80
--memory=256m
Sets a 256 MiB memory limit
myapp:latest
Uses the required Docker image
Docker documents all these options as supported container-runtime settings.
Docker Docs
Step 13: Understand detached mode.
The -d option means detached mode.
When executed with -d, Docker starts the container in the background and returns control to the terminal.
For example:
does not attach the terminal to the container's standard input and output.
Instead, Docker normally prints the new container ID.
The task explicitly requests a detached container, so do not omit -d.
Also, do not use --rm for this task. Removing a container automatically on exit conflicts with the intended persistent container lifecycle.
Step 14: Understand the required port mapping.
The task states:
mapping the container port 80/tcp to host port 8080/tcp
The correct argument is:
Docker port-publishing syntax is:
Therefore:
A connection to:
is forwarded to TCP port 80 inside the container.
Do not reverse the numbers:
That would map host port 80 to container port 8080, which is the opposite of the task's requirement.
By default, publishing without a specific host IP address exposes the port on the Docker host's available network interfaces, subject to network and firewall configuration.
Docker Docs
Step 15: Understand the 256m memory limit.
The required option is:
This configures a hard limit on the container's physical memory usage.
Docker interprets this memory size as:
256
×
1024
×
1024
=
268
,
435
,
456
bytes
256×1024×1024=268,435,456 bytes
Therefore, the configured memory value is:
The memory limit is enforced through Linux kernel resource-management mechanisms, such as control groups (cgroups).
One distinction matters: --memory=256m limits physical memory, but Docker may permit additional swap usage depending on its swap configuration.
The task does not separately specify a swap limit. Therefore, --memory=256m is the appropriate requested setting without introducing unrelated swap restrictions.
Docker Docs
Step 16: Understand automatic container restart behavior.
The final requirement is:
Finally, ensure that the container is started automatically on boot or restart of Docker.
Docker supports several restart policies.
Restart policy
Behavior
no
No automatic restart
on-failure
Restart after a failed process exit, subject to options
always
Restart when the container exits and after applicable Docker daemon restarts unless-stopped Similar to always, but retains a manually stopped state across daemon restarts For this task, use:
This is appropriate because the task specifically requires automatic startup after boot or a Docker daemon restart.
Docker documents that a manually stopped container using always is normally restarted when the Docker daemon restarts, unlike unless-stopped.
Docker Docs
Step 17: Verify that the container was created and started.
Execute:
A successful result should include a container using:
Its status should indicate that it is running.
For example:
This is an illustrative result.
If no running container appears, inspect stopped containers:
A successful docker run -d response only confirms that Docker accepted the startup request; it does not guarantee the application continues running.
Step 18: Verify the image used by the container.
Execute:
Expected:
This confirms that the running container was created using the required image reference.
Docker's official inspect documentation supports using formatted output to retrieve individual container configuration fields.
Docker Docs
Step 19: Verify the container's TCP port mapping.
Execute:
Expected output includes a mapping equivalent to:
Depending on the host configuration, Docker may also display an IPv6 mapping.
For a targeted check:
This should identify host TCP port 8080.
The docker port command is specifically documented for inspecting published port mappings.
Docker Docs
Step 20: Verify the configured memory limit.
Execute:
Expected:
This confirms the configured 256 MiB limit.
You can also examine runtime resource usage:
This displays the current memory consumption and configured memory limit.
An illustrative result might show:
The actual usage depends on the application.
Step 21: Verify the automatic restart policy.
Execute:
Expected output:
This confirms that the Docker container has the required restart policy.
If an otherwise correctly configured container was created without that setting, the restart policy can be corrected using:
There is no need to recreate the container solely to change its restart policy.
Docker Docs
Step 22: Ensure Docker itself starts at boot.
A container restart policy works when the Docker daemon is running.
Check whether the Docker service is enabled:
Expected:
On Ubuntu, Docker is commonly enabled to start automatically at boot.
If it is disabled, execute:
Where containerd.service is installed and is part of the Docker Engine setup, verify that its startup configuration is appropriate as well.
Docker's official Linux post-installation documentation recommends enabling Docker and containerd services for boot-time startup on systemd-based systems when they are not already enabled.
Docker Docs
Step 23: Test the application through host port 8080.
If the Dockerfile starts an HTTP application on port 80, execute:
A valid HTTP response confirms that the host's published port can reach the containerized application.
For example:
The actual response code depends on the application's configuration.
An HTTP response is an application-level test. The Docker task itself requires the port mapping to be configured correctly, so do not confuse an application error with an incorrect port-publishing setting without further investigation.
Step 24: Troubleshoot a container that exits unexpectedly.
If the container does not remain running, execute:
Check its current state.
Then inspect its logs:
Common causes of immediate container exit include:
An invalid startup command.
A missing application dependency.
An application configuration error.
Failure of the image's main process.
Memory exhaustion.
Do not assume that --restart=always repairs application failures.
Docker's restart policy takes effect after a container has started successfully, with Docker documenting a minimum successful startup period of approximately ten seconds before restart monitoring applies.
NEW QUESTION # 53
Which of the following commands will help identify a broken router between the local and the remote machine?
Answer: A
NEW QUESTION # 54
CORRECT TEXT
Which port is the default server port for the HTTPS protocol? (Specify the port number using digits.)
Answer:
Explanation:
443
NEW QUESTION # 55
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