Free Practice Questions for LPI 305-300 Exam

 A Pod in Kubernetes is a collection of one or more containers that share the same network and storage resources, and a specification for how to run the containers. A Pod is the smallest unit of workload Kubernetes can run, meaning that it cannot be divided into smaller units. Therefore, option C is correct. All containers of a Pod run on the same node, which is the smallest unit of computing hardware in Kubernetes. A node is a physical or virtual machine that hosts one or more Pods. Therefore, option A is also correct. Pods are not always created automatically and cannot be explicitly configured. Pods can be created manually using YAML or JSON files, or using commands like kubectl run or kubectl create. Pods can also be created automatically by higher-level controllers, such as Deployment, ReplicaSet, or StatefulSet. Therefore, option B is incorrect. When a Pod fails, Kubernetes does not restart the Pod on another node by default. Pods are ephemeral by nature, meaning that they can be terminated or deleted at any time. If a Pod is managed by a controller, the controller will create a new Pod to replace the failed one, but it may not be on the same node. Therefore, option D is incorrect. systemd is not used to manage individual Pods on the Kubernetes nodes. systemd is a system and service manager for Linux operating systems that can start and stop services, such as docker or kubelet. However, systemd does not interact with Podsdirectly. Pods are managed by the kubelet service, which is an agent that runs on each node and communicates with the Kubernetes control plane. Therefore, option E is incorrect. References:

Pods | Kubernetes

What is a Kubernetes pod? - Red Hat

What’s the difference between a pod, a cluster, and a container?

What are Kubernetes Pods? | VMware Glossary

Kubernetes Node Vs. Pod Vs.Cluster: Key Differences - CloudZero

The firmware attribute of the element in a libvirt domain definition specifies the type of firmware used to boot the virtual machine. The valid values for this attribute are efi and bios, which correspond to the Extensible Firmware Interface (EFI) and the Basic Input/Output System (BIOS) respectively. EFI is a newer standard that supports more features and security than BIOS, such as Secure Boot and faster boot times. BIOS is an older standard that is widely compatible and supported by most hypervisors and operating systems. The other values, scsi, virtio, and pcie, are not related to firmware, but to different types of devices or drivers that can be used in a virtual machine. References: 1 (search for firmware enum)

LXC implements system containers, which are a type of operating-system-level virtualization. System containers allow running multiple isolated Linux systems on a single Linux control host, using a single Linux kernel. System containers share the same kernel with the host and each other, but have their own file system, libraries, andprocesses. System containers are different from application containers, which are designed to run a single application or service in an isolated environment. Application containers are usually smaller and more portable than system containers, but also more dependent on the host kernel and libraries. Hardware containers, CPU emulation, and paravirtualization are not related to LXC, as they are different kinds of virtualization methods that involve hardware abstraction, instruction translation, or modification of the guest operating system. References:

1: LXC - Wikipedia

2: Linux Virtualization : Linux Containers (lxc) - GeeksforGeeks

3: Features - Proxmox Virtual Environment

 Libvirt is a toolkit that provides a common API for managing different virtualization technologies, such as KVM, Xen, LXC, and others. Libvirt allows users to configure and control various aspects of a virtual machine (also called a domain), such as its CPU, memory, disk, network, and other resources. Among the resources that can be limited by libvirt for a KVM domain are:

Amount of CPU time: Libvirt allows users to specify the number of virtual CPUs (vCPUs) that a domain can use, as well as the CPU mode, model, topology, and tuning parameters. Users can also set the CPU shares, quota, and period to control the relative or absolute amount of CPU time that a domain can consume. Additionally, users can pin vCPUs to physical CPUs or NUMA nodes to improve performance and isolation. These settings can be configured in the domain XML file under the  and  elements12.

Size of available memory: Libvirt allows users to specify the amount of memory that a domain can use, as well as the memory backing, tuning, and NUMA node parameters. Users can also set the memory hard and soft limits, swap hard limit, and minimum guarantee to control the memory allocation and reclaim policies for a domain. These settings can be configured in the domain XML file under the , , and  elements13.

The other resources listed in the question are not directly limited by libvirt for a KVM domain. File systems allowed in the domain are determined by the disk and filesystem devices that are attached to the domain, which can be configured in the domain XML file under the  and  elements14. Number of running processes and number of available files are determined by the operating system and the file system of the domain, which are not controlled by libvirt.

References:

libvirt: Domain XML format

CPU Allocation

Memory Allocation

Hard drives, floppy disks, CDROMs

The command docker run -tid -v data:/data debian bash creates and runs a new container from the debian image, with an interactive terminal and a detached mode, and mounts a named volume data at /data in the container12. If the volume data does not exist, it is created automatically3. If the command is executed twice in succession, two containers are created and run, each with its own terminal and process ID, but they share the same volume data. This means that both containers can access, modify, and see the contents of the data volume, and any changes made by one container are reflected in the other container. Therefore, the statement C is true and the correct answer. The statements A, B, D, and E are false and incorrect, as they do not describe the behavior of the command or the volume correctly. References:

1: docker run | Docker Docs.

2: Docker run reference | Docker Docs - Docker Documentation.

3: Use volumes | Docker Documentation.

[4]: How to Use Docker Run Command with Examples - phoenixNAP.

IaaS is a type of cloud computing service that offers essential compute, storage, and networking resources on demand, on a pay-as-you-go basis. IaaS is one of the four types of cloud services, along with software as a service (SaaS), platform as a service (PaaS), and serverless12. IaaS eliminates the need for enterprises to procure, configure, or manage infrastructure themselves, and they only pay for what they use23. Some examples of IaaS providers are Microsoft Azure, Google Cloud, and Amazon Web Services.

 LXC and Docker are both container technologies that use Linux kernel features to create isolated environments for running applications. The main mechanisms that they use are:

Linux Capabilities: These are a set of privileges that can be assigned to processes to limit their access to certain system resources or operations. For example, a process with the CAP_NET_ADMIN capability can perform network administration tasks, such as creating or deleting network interfaces. Linux capabilities allow containers to run with reduced privileges, enhancing their security and isolation.

Kernel Namespaces: These are a way of creating separate views of the system resources for different processes. For example, a process in a mount namespace can have a different file system layout than the host or other namespaces. Kernel namespaces allow containers to have their own network interfaces, process IDs, user IDs, and other resources, without interfering with the host or other containers.

Control Groups: These are a way of grouping processes and applying resource limits and accounting to them. For example, a control group can limit the amount of CPU, memory, disk I/O, or network bandwidth that a process or a group of processes can use. Control groups allow containers to have a fair share of the system resources and prevent them from exhausting the host resources.

POSIX ACLs and file system permissions are not mechanisms used by LXC and Docker to create containers. They are methods of controlling the access to files and directories on a file system, which can be applied to any process, not just containers.

References:

LXC vs Docker: Which Container Platform Is Right for You?

LXC vs Docker: Why Docker is Better in 2023 | UpGuard

What is the Difference Between LXC, LXD and Docker Containers

lxc - Which container implementation docker is using - Unix & Linux Stack Exchange

Sparse images are a type of virtual disk images that grow in size as data is written to them, but do not shrink when data is deleted from them. Sparse images may consume an amount of space different from their nominal size, which is the maximum size that the image can grow to. For example, a sparse image with a nominal size of 100 GB may only take up 20 GB of physical storage if only 20 GB of data is written to it. Sparse images allocate backend storage at the first usage of a block, which means that the physical storage is only used when the virtual machine actually writes data to a block. This can save storage space and improve performance, as the image does not need to be pre-allocated or zeroed out.

Sparse images are not automatically shrunk when files within the image are deleted, because the virtual machine does not inform the host system about the freed blocks. To reclaim the unused space, a special tool such as virt-sparsify1 or qemu-img2 must be used to compact the image. Sparse images can be used with both full virtualization and paravirtualization, as the type of virtualization does not affect the format of the disk image. Sparse images are not automatically resized when their maximum capacity is about to be exceeded, because this would require changing the partition table and the filesystem of the image, which is not a trivial task. To resize a sparse image, a tool such as virt-resize3 or qemu-img2 must be used to increase the nominal size and the filesystem size of the image. References: 1 (search for “virt-sparsify”), 2 (search for “qemu-img”), 3 (search for “virt-resize”).