Free Practice Questions for LPI 305-300 Exam

The purpose of the kubelet service in Kubernetes is to run containers on the worker nodes according to the Kubernetes configuration. The kubelet is an agent or program that runs on each node and communicates with the Kubernetes control plane. It receives a set of PodSpecs that describe the desired state of the pods that should be running on the node, and ensures that the containers described in those PodSpecs are running and healthy. The kubelet also reports the status of the node and the pods back to the control plane. The kubelet does not manage containers that were not created by Kubernetes. References:

Kubernetes Docs - kubelet

Learn Steps - What is kubelet and what it does: Basics on Kubernetes

A hypervisor is a software that creates and runs virtual machines (VMs) by separating the operating system and resources from the physical hardware. One of the main tasks of a hypervisor is to map the resources of VMs to the resources of the host system, such as CPU, memory, disk, and network. This allows the hypervisor to allocate and manage the resources among multiple VMs and ensure that they run efficiently and independently123. Another important task of a hypervisor is to isolate the VMs and prevent unauthorized access to resources of other VMs. This ensures the security and privacy of the VMs and their data, as well as the stability and performance of the host system. The hypervisor can use various techniques to isolate the VMs, such as virtual LANs, firewalls, encryption, and access control145.

The other tasks listed are not part of a hypervisor’s responsibility, but rather of the guest operating system or the application running inside the VM. A hypervisor does not create filesystems during the installation of new VMs, as this is done by the installer of the guest operating system6. A hypervisor does not provide host-wide unique PIDs to the processes running inside the VMs, as this is done by the kernel of the guest operating system7. A hypervisor does not manage authentication to network services running inside a VM, as this is done by the network service itself or by a directory service such as LDAP or Active Directory8. References: 1 (search for “What is a hypervisor?”), 2 (search for “How does a hypervisor work?”), 3 (search for “The hypervisor gives each virtual machine the resources that have been allocated”), 4 (search for “Benefits ofhypervisors”), 5 (search for “Isolate the virtual machines and prevent unauthorized access”), 6 (search for “Create filesystems during the installation of new virtual machine quest operating systems”), 7 (search for “Provide host-wide unique PIDs to the processes running inside the virtual machines”), 8 (search for “Manage authentication to network services running inside a virtual machine”).

The command virsh pool-create-as vms dir --target /vms creates and starts a transient storage pool named vms of type dir with the target directory /vms12. This command resolves the issue of the storage pool not found error, as it makes the existing directory /vms visible to libvirt as a storage pool. The other commands are invalid because:

dd if=/dev/zero of=/vms bs=1 count=0 flags=name:vms is not a valid command syntax. The dd command does not take a flags argument, and the output file /vms should be a regular file, not a directory3.

libvirt-poolctl new --name=/vms --type=dir --path=/vms is not a valid command name. There is no such command as libvirt-poolctl in the libvirt package4.

qemu-img pool vms:/vms is not a valid command syntax. The qemu-img command does not have a pool subcommand, and the vms:/vms argument is not a valid image specification5.

touch /vms/.libvirtpool is not a valid command to create a storage pool. The touch command only creates an empty file, and the .libvirtpool file is not recognized by libvirt as a storage pool configuration file6.

References:

1: virsh - difference between pool-define-as and pool-create-as - Stack Overflow

2: dd(1) - Linux manual page - man7.org

3: 12.3.3. Creating a Directory-based Storage Pool with virsh - Red Hat Customer Portal

4: libvirt - Linux Man Pages (3)

5: qemu-img(1) - Linux manual page - man7.org

6: touch(1) - Linux manual page - man7.org

 The command virsh list is used to list all running domains (VMs) on the current host. The command virsh list --all can be used to list both active and inactive domains. The other options are not valid virsh commands. The command virsh list is a basic command that lists all running domains (VMs). You can also list all configured VMs by adding the --all option. This is useful if you want to see all VMs configured in the target hypervisor that you can use on subsequent commands1. References:

1: 8 Linux virsh subcommands for managing VMs on the command line | Enable Sysadmin.

 The command vagrant init is used to initialize the current directory to be a Vagrant environment by creating an initial Vagrantfile if one does not already exist1. The Vagrantfile contains the configuration settings for the Vagrant box, such as the box name, box URL, network settings, synced folders, provisioners, etc. The command vagrant init does not execute any provisioning tool, start any box, install Vagrant on a Linux host, or download any box. Those actions are performed by other Vagrant commands, such as vagrant provision, vagrant up, vagrant install, and vagrant box add, respectively. References:

1: vagrant init - Command-Line Interface | Vagrant | HashiCorp Developer

The ENTRYPOINT instruction in a Dockerfile specifies the default command to run when a container is started from the image. The ENTRYPOINT instruction can be written in two forms: exec form and shell form. The exec form uses a JSON array to specify the command and its arguments, such as [ “executable”, “param1”, “param2” ]. The shell form uses a single string to specify the command and its arguments, such as “executable param1 param2”. The shell form is converted to the exec form by adding /bin/sh -c to the beginning of the command. Therefore, the following statements in a Dockerfile are equivalent and will lead to a container that outputs hello world:

ENTRYPOINT [ “echo hello world” ] ENTRYPOINT [ “/bin/sh”, “-c”, “echo hello world” ] ENTRYPOINT “echo hello world” ENTRYPOINT [ “echo”, “hello”, “world” ] ENTRYPOINT [ “/bin/sh”, “-c”, “echo”, “hello”, “world” ] ENTRYPOINT “echo hello world”

The other statements in the question are invalid or incorrect. The statement A. ENTRYPOINT “echo Hello World” is invalid because it uses double quotes to enclose the entire command, which is not allowed in the shell form. The statement D. ENTRYPOINT echo Hello World is incorrect because it does not use quotes to enclose the command, which is required in the shell form. The statement E. ENTRYPOINT “echo”, “Hello”, “World” is invalid because it uses double quotes to separate the command and its arguments, which is not allowed in the exec form. References:

Dockerfile reference | Docker Docs

Using the Dockerfile ENTRYPOINT and CMD Instructions - ATA Learning

Difference Between run, cmd and entrypoint in a Dockerfile

The command that deletes all volumes which are not associated with a container is docker volume prune. This command removes all unused local volumes, which are those that are not referenced by any containers. By default, it only removes anonymous volumes, which are those that are not given a specific name when they are created. To remove both unused anonymous and named volumes, the --all or -a flag can be added to the command. The command will prompt for confirmation before deleting the volumes, unless the --force or -f flag is used to bypass the prompt. The command will also show the total reclaimed space after deleting the volumes12.

The other commands listed in the question are not valid or do not have the same functionality as docker volume prune. They are either made up, misspelled, or have a different purpose. These commands are:

docker volume cleanup: This command does not exist in Docker. There is no cleanup subcommand for docker volume.

docker volume orphan -d: This command does not exist in Docker. There is no orphan subcommand for docker volume, and the -d flag is not a valid option for any docker volume command.

docker volume vacuum: This command does not exist in Docker. There is no vacuum subcommand for docker volume.

docker volume garbage-collect: This command does not exist in Docker. There is no garbage-collect subcommand for docker volume.

References:

docker volume prune | Docker Docs

How to Remove all Docker Volumes - YallaLabs.

Resource management for full virtualization is the process of allocating and controlling the physical resources of the host system to the virtual machines running on it. The hypervisor is the software layer that performs this task, by providing each virtual machine with a virtual hardware of a defined capacity that limits the resources of the virtual machine. For example, the hypervisor can specify how many virtual CPUs, how much memory, and how much disk space each virtual machine can use. The hypervisor can also enforce resource isolation and prioritization among the virtual machines, to ensure that they do not interfere with each other or consume more resources than they are allowed to. The hypervisor cannot provide fine-grained limits to internal elements of the guest operating system, such as the number of processes, because the hypervisor does not have access to the internal state of the guest operating system. The guest operating system is responsible for managing its own resources within the virtual hardware provided by the hypervisor. For example, the guest operating system can create an arbitrary amount of network sockets, as long as it does not exceed the network bandwidth allocated by the hypervisor. Full virtualization can pose limits to virtual machines, and does not always assign the host system’s resources in a first-come-first-serve manner. The hypervisor can use various resource management techniques, such as reservation, limit, share, weight, and quota, to allocate and control the resources of the virtual machines. The hypervisor can also use resource scheduling algorithms, such as round-robin, fair-share, or priority-based, to distribute the resources among the virtual machines according to their needs and preferences. All processes created within the virtual machines are not transparently and equally scheduled in the host system for CPU and I/O usage. The hypervisor can use different scheduling policies, such as proportional-share, co-scheduling, or gang scheduling, to schedule the virtual CPUs of the virtual machines on the physical CPUs of the host system. The hypervisor can alsouse different I/O scheduling algorithms, such as deadline, anticipatory, or completely fair queuing, to schedule the I/O requests of the virtual machines on the physical I/O devices of the host system. The hypervisor can also use different resource accounting and monitoring mechanisms, such as cgroups, perf, or sar, to measure and report the resource consumption and performance of the virtual machines. References:

Oracle VM VirtualBox: Features Overview

Resource Management as an Enabling Technology for Virtualization - Oracle

Introduction to virtualization and resource management in IaaS | Cloud Native Computing Foundation

 The Linux kernel module that must be loaded in order to use QEMU with hardware virtualization extensions is KVM (Kernel-based Virtual Machine). KVM is a full virtualization solution that allows a user space program (such as QEMU) to utilize the hardware virtualization features of various processors (such as Intel VT or AMD-V). KVM consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko. KVM must be loaded into the kernel of the host system in order to use the virtualization extensions of the host system’s CPU. This enables QEMU to run multiple virtual machines with unmodified Linux or Windows images, each with private virtualized hardware. KVM is integrated with QEMU, so there is no need to load it into the kernel of each virtual machine or the first virtual machine. KVM also does not require paravirtualization, which is a technique that modifies the guest operating system to communicate directly with the hypervisor, bypassing the emulation layer. References:

Features/KVM - QEMU

Kernel-based Virtual Machine

KVM virtualization on Red Hat Enterprise Linux 8 (2023)